News Keeps Getting Worse for Vitamins

November 20, 2008, 12:45 pm 


The best efforts of the scientific community to prove the health benefits of vitamins keep falling short. 

Consumers don’t want to give up their vitamins. (Tony Cenicola/The New York Times)

This week, researchers reported the disappointing results from a large clinical trial of almost 15,000 male doctors taking vitamins E and C for a decade. The study showed no meaningful effect on cancer rates.

Another recent study found no benefit of vitamins E and C for heart disease.

In October, a major trial studying whether vitamin E and selenium could lower a man’s risk for prostate cancer ended amidst worries that the treatments may do more harm than good.

And recently, doctors at Memorial Sloan-Kettering Cancer Center in New York warned that vitamin C seems to protect not just healthy cells but cancer cells, too.

Everyone needs vitamins, which are critical for the body. But for most people, the micronutrients we get from foods usually are adequate to prevent vitamin deficiency, which is rare in the United States. That said, some extra vitamins have proven benefits, such as vitamin B12 supplements for the elderly and folic acid for women of child-bearing age. And calcium and vitamin D in women over 65 appear to protect bone health.

But many people gobble down large doses of vitamins believing that they boost the body’s ability to mop up damaging free radicals that lead to cancer and heart disease. In addition to the more recent research, several reports in recent years have challenged the notion that megadoses of vitamins are good for you.

A Johns Hopkins School of Medicine review of 19 vitamin E clinical trials of more than 135,000 people showed high doses of vitamin E (greater than 400 IUs) increased a person’s risk for dying during the study period by 4 percent. Taking vitamin E with other vitamins and minerals resulted in a 6 percent higher risk of dying. Another study of daily vitamin E showed vitamin E takers had a 13 percent higher risk for heart failure.

The Journal of Clinical Oncology published a study of 540 patients with head and neck cancer who were being treated with radiation therapy. Vitamin E reduced side effects, but cancer recurrence rates among the vitamin users were higher, although the increase didn’t reach statistical significance.

A 1994 Finland study of smokers taking 20 milligrams a day of beta carotene showed an 18 percent higher incidence of lung cancer among beta carotene users. In 1996, a study called Caret looked at beta carotene and vitamin A use among smokers and workers exposed to asbestos, but the study was stopped when the vitamin users showed a 28 percent higher risk for lung cancer and a 26 percent higher risk of dying from heart disease.

A 2002 Harvard study of more than 72,000 nurses showed that those who consumed high levels of vitamin A from foods, multivitamins and supplements had a 48 percent higher risk for hip fractures than nurses who had the lowest intake of vitamin A. 

The Cochrane Database of Systematic Reviews looked at vitamin C studies for treating colds. Among more than two dozen studies, there was no overall benefit for preventing colds, although the vitamin was linked with a 50 percent reduction in colds among people who engaged in extreme activities, such as marathon runners, skiers and soldiers, who were exposed to significant cold or physical stress. The data also suggested vitamin C use was linked with less severe and slightly shorter colds. 

In October 2004, Copenhagen researchers reviewed seven randomized trials of beta carotene, selenium and vitamins A, C and E (alone or in combination) in colon, esophageal, gastric, pancreatic and liver cancer. The antioxidant users had a 6 percent higher death rate than placebo users. 

Two studies presented to the American College of Cardiology in 2006 showed that vitamin B doesn’t prevent heart attacks, leading The New England Journal of Medicine to say that the consistency of the results “leads to the unequivocal conclusion” that the vitamins don’t help patients with established vascular disease.

The British Medical Journal looked at multivitamin use among elderly people for a year but found no difference in infection rates or visits to doctors.

Despite a lack of evidence that vitamins actually work, consumers appear largely unwilling to give them up. Many readers of the Well blog say the problem is not the vitamin but poorly designed studies that use the wrong type of vitamin, setting the vitamin up to fail. Industry groups such as the Council for Responsible Nutrition also say the research isn’t well designed to detect benefits in healthy vitamin users.

Lack of Exercise Explains Depression-Heart Link

November 26, 2008, 2:43 pm

By Tara Parker-Pope

For years cardiologists and mental health experts have known that depression raises risk for heart attack by 50 percent or more. 

But what hasn’t been clear is why depressed people have more heart problems. Does depression cause some biological change that increases risk? Does the inflammatory process that leads to heart disease also trigger depression? 

The answer may be far simpler. A new study suggests that people who are depressed are simply less likely to exercise, a finding that explains their dramatically higher risk for heart problems.

Researchers, led by doctors from the Veterans Affairs Medical Center in San Francisco, recruited 1,017 participants with heart disease to track their health and lifestyle habits. As they expected, those patients who had symptoms of depression fared worse. About 10 percent of depressed heart patients had additional heart problems, during the study, compared with 6.7 percent of the other patients. After controlling for other illnesses and the severity of heart disease, the finding translates to a 31 percent higher risk of heart problems among the depressed people, according to the study published this week in the Journal of the American Medical Association.

But once the researchers factored in the effect of exercise, the difference in risk among depressed people disappeared. In the same study, patients who didn’t exercise, whether or not they were depressed, had a 44 percent higher risk of heart problems, after controlling for a variety of factors including medication adherence, smoking and other illnesses.

The findings are important because some earlier studies have suggested a link between antidepressant use and lower heart risk. The explanation may be that patients who take antidepressants start to feel better and take care of themselves, adopting healthy behaviors including exercise. In a study of nearly 2,500 heart-attack patients, published in the Journal of the American Medical Association in June 2003, behavioral therapy to treat depression didn’t change survival rates compared with patients who received regular care. But among about 20 percent of patients in the study who ended up on antidepressants, the risk of dying or suffering a second nonfatal heart attack was 42 percent lower. Another study, called Sadheart (which stands for Sertraline Antidepressant Heart Attack Randomized Trial) showed the death rate from heart-related problems was 20 percent lower among patients taking the drug, although the data weren’t statistically significant.

The research suggests that doctors treating patients for depression should also talk to them about their lifestyle habits, and encourage them to exercise. The findings, say the researchers, suggest that the heart problems associated with depression “could potentially be preventable.”

The evidence that health behaviors fully explain the link between depression and heart disease in this study is convincing, says Dr. Mary A. Whooley, professor of medicine, epidemiology and biostatistics at the University of California, San Francisco. However, she notes the study is limited to older men with stable coronary disease, and as a result, more study is needed of women and other patients with heart disease.

It remains an open question whether the study findings will change the way doctors counsel their patients. “The clinical practice question is a challenging one,” says Dr. Whooley. “It’s easy for us to tell patients to exercise, take their medicines, and refrain from smoking, but actually changing health behaviors is very difficult.”

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Scientists Find Clues to Aging in a Red Wine Ingredient’s Role in Activating a Protein

November 27, 2008

By NICHOLAS WADE

A new insight into the reason for aging has been gained by scientists trying to understand how resveratrol, a minor ingredient of red wine, improves the health and lifespan of laboratory mice. They believe that the integrity of chromosomes is compromised as people age, and that resveratrol works by activating a protein known as sirtuin that restores the chromosomes to health.

The finding, published online Wednesday in the journal Cell, is from a group led by David Sinclair of the Harvard Medical School. It is part of a growing effort by biologists to understand the sirtuins and other powerful agents that control the settings on the living cell’s metabolism, like its handling of fats and response to insulin. 

Researchers are just beginning to figure out how these agents work and how to manipulate them, hoping that they can develop drugs to enhance resistance to disease and to retard aging.

Sirtris, a company Dr. Sinclair helped found, has developed a number of chemicals that mimic resveratrol and are potentially more suitable as drugs since they activate sirtuin at much lower doses than resveratrol. This month, one of these chemicals was reported in the journal Cell Metabolism to protect mice on fatty diets from getting obese and to enhance their endurance in treadmills, just as resveratrol does.

Though the sirtuin field holds considerable promise, the dust has far from settled. Resveratrol is a powerful agent with many different effects, only some of which are exerted through sirtuin. So drugs that activate sirtuin may not be as splendid a tonic for people as resveratrol certainly seems to be for mice. 

The new finding concerns maintenance of the chromosomes, the giant molecules of DNA that make up the genome. 

Each cell has six feet of DNA packed into its nucleus, carrying the 20,000 or so genetic instructions needed to operate the human body. Each cell must provide instant access to the handful of these genes needed by its cell type, but also keep the rest firmly switched off to avoid chaos. 

Sirtuin’s normal role is to help gag all the genes that a cell needs to keep suppressed. It does so by keeping the chromatin, the stuff that wraps around the DNA, packed so tightly that the cell cannot get access to the underlying genes.

But sirtuin has another critical role, one that is triggered by emergencies like a break in both DNA strands of a chromosome. After a double strand break, sirtuin rushes to the site to help knit the two parts of the chromosome back together. But in this salvage operation, it leaves its post, and the genes it was repressing are liable to come back into action, causing mayhem. 

This, Dr. Sinclair and his colleagues suggest, may be a fundamental cause of aging in mice and probably people, too. 

The gene-gagging role of sirtuin was discovered in the 1980s by biologists studying yeast, a standard laboratory organism. Dr. Sinclair and Leonard Guarente of the Massachusetts Institute of Technology found in 1997 that sirtuin could also repair a certain kind of genomic damage in yeast, and in doing so extended the yeast cell’s lifespan. But this particular kind of damage does not occur in mammalian cells, raising the puzzle of why extra sirtuin should be good for them.

Dr. Sinclair’s new report, if verified, resolves this problem by showing that sirtuin has retained its genomic repair role in higher organisms but that the repair is focused on a different kind of genomic damage — that of breaks in a chromosome.

These experiments “elegantly demonstrate” that sirtuin works in much the same way in mammals as in yeast, Dr. Jan Vijg of the Albert Einstein College of Medicine wrote in a commentary in Cell. The question now is whether sirtuin is a pro-longevity factor in mammals, he said in an e-mail message. 

Ronald Evans, a biologist at the Salk Institute, said the new report was provocative but did not prove the case that the relocation of sirtuin was a cause of aging. Tests with mice genetically engineered to lack the sirtuin gene could show if the mice suffered from premature aging, as Dr. Sinclair’s idea would predict.

Dr. Sinclair said he agreed that the case for sirtuin’s role in aging had not been proved. “We are careful not to say this is the cause of aging, but based on everything we know it’s not a bad hypothesis,” he said. 

It would be nice to test aging in mice that lack the sirtuin gene, as Dr. Evans proposed, but they die too young, Dr. Sinclair said.

Dr. Sinclair has been taking large daily doses of resveratrol since he and others discovered five years ago that it activated sirtuin. “I’m still taking it, and I feel great,” he said, “but it’s too early to say if I’m young for my age.” 

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Study Suggests Some Cancers May Go Away

November 25, 2008
 
By GINA KOLATA

Cancer researchers have known for years that it was possible in rare cases for some cancers to go away on their own. There were occasional instances of melanomas and kidney cancers that just vanished. And neuroblastoma, a very rare childhood tumor, can go away without treatment.

But these were mostly seen as oddities — an unusual pediatric cancer that might not bear on common cancers of adults, a smattering of case reports of spontaneous cures. And since almost every cancer that is detected is treated, it seemed impossible even to ask what would happen if cancers were left alone.

Now, though, researchers say they have found a situation in Norway that has let them ask that question about breast cancer. And their new study, to be published Tuesday in The Archives of Internal Medicine, suggests that even invasive cancers may sometimes go away without treatment and in larger numbers than anyone ever believed.

At the moment, the finding has no practical applications because no one knows whether a detected cancer will disappear or continue to spread or kill. 

And some experts remain unconvinced. 

“Their simplification of a complicated issue is both overreaching and alarming,” said Robert A. Smith, director of breast cancer screening at the American Cancer Society.

But others, including Robert M. Kaplan, the chairman of the department of health services at the School of Public Health at the University of California, Los Angeles, are persuaded by the analysis. The implications are potentially enormous, Dr. Kaplan said. 

If the results are replicated, he said, it could eventually be possible for some women to opt for so-called watchful waiting, monitoring a tumor in their breast to see whether it grows. “People have never thought that way about breast cancer,” he added.

Dr. Kaplan and his colleague, Dr. Franz Porzsolt, an oncologist at the University of Ulm, said in an editorial that accompanied the study, “If the spontaneous remission hypothesis is credible, it should cause a major re-evaluation in the approach to breast cancer research and treatment.”

The study was conducted by Dr. H. Gilbert Welch, a researcher at the VA Outcomes Group in White River Junction, Vt., and Dartmouth Medical School; Dr. Per-Henrik Zahl of the Norwegian Institute of Public Health; and Dr. Jan Maehlen of Ulleval University Hospital in Oslo. It compared two groups of women ages 50 to 64 in two consecutive six-year periods. 

One group of 109,784 women was followed from 1992 to 1997. Mammography screening in Norway was initiated in 1996. In 1996 and 1997, all were offered mammograms, and nearly every woman accepted.

The second group of 119,472 women was followed from 1996 to 2001. All were offered regular mammograms, and nearly all accepted. 

It might be expected that the two groups would have roughly the same number of breast cancers, either detected at the end or found along the way. Instead, the researchers report, the women who had regular routine screenings had 22 percent more cancers. For every 100,000 women who were screened regularly, 1,909 were diagnosed with invasive breast cancer over six years, compared with 1,564 women who did not have regular screening.

There are other explanations, but researchers say that they are less likely than the conclusion that the tumors disappeared.

The most likely explanation, Dr. Welch said, is that “there are some women who had cancer at one point and who later don’t have that cancer.” 

The finding does not mean that mammograms caused breast cancer. Nor does it bear on whether women should continue to have mammograms, since so little is known about the progress of most cancers.

Mammograms save lives, Dr. Smith said. Even though they can have a downside — most notably the risk that a woman might have a biopsy to check on an abnormality that turns out not to be cancer — “the balance of benefits and harms is still considerably in favor of screening for breast cancer,” he said.

But Dr. Suzanne W. Fletcher, an emerita professor of ambulatory care and prevention at Harvard Medical School, said that it was also important for women and doctors to understand the entire picture of cancer screening. The new finding, she said, was “part of the picture.” 

“The issue is the unintended consequences that can come with our screening,” Dr. Fletcher said, meaning biopsies for lumps that were not cancers or, it now appears, sometimes treating a cancer that might not have needed treatment. “In general we tend to underplay them.” 

Dr. Welch said the cancers in question had broken through the milk ducts, where most breast cancers begin, and invaded the breast. Such cancers are not microscopic, often are palpable, and are bigger and look more ominous than those confined to milk ducts, so-called ductal carcinoma in situ, or DCIS, Dr. Welch said. Doctors surgically remove invasive cancers and, depending on the circumstances, may also treat women with radiation, chemotherapy or both.

The study’s design was not perfect, but researchers say the ideal study is not feasible. It would entail screening women, randomly assigning them to have their screen-detected cancers treated or not, and following them to see how many untreated cancers went away on their own.

But, they said, they were astonished by the results.

“I think everybody is surprised by this finding,” Dr. Kaplan said. He and Dr. Porzsolt spent a weekend reading and re-reading the paper.

“Our initial reaction was, ‘This is pretty weird,’ ” Dr. Kaplan said. “But the more we looked at it, the more we were persuaded.”

Dr. Barnett Kramer, director of the Office of Disease Prevention at the National Institutes of Health, had a similar reaction. “People who are familiar with the broad range of behaviors of a variety of cancers know spontaneous regression is possible,” he said. “But what is shocking is that it can occur so frequently.”

Although the researchers cannot completely rule out other explanations, Dr. Kramer said, “they do a good job of showing they are not highly likely.” 

A leading alternative explanation for the results is that the women having regular scans used hormone therapy for menopause and the other women did not. But the researchers calculated that hormone use could account for no more than 3 percent of the effect. 

Maybe mammography was more sensitive in the second six-year period, able to pick up more tumors. But, the authors report, mammography’s sensitivity did not appear to have changed. 

Or perhaps the screened women had a higher cancer risk to begin with. But, the investigators say, the groups were remarkably similar in their risk factors. 

Dr. Smith, however, said the study was flawed and the interpretation incorrect. Among other things, he said, one round of screening in the first group of women would never find all the cancers that regular screening had found in the second group. The reason, he said, is that mammography is not perfect, and cancers that are missed on one round of screening will be detected on another.

But Dr. Welch said that he and his colleagues considered that possibility, too. And, he said, their analysis found subsequent mammograms could not make up the difference.

Dr. Kaplan is already thinking of how to replicate the result. One possibility, he said, is to do the same sort of study in Mexico, where mammography screening is now being introduced.

Donald A. Berry, chairman of the department of biostatistics at M. D. Anderson Cancer Center in Houston, said the study increased his worries about screenings that find cancers earlier and earlier. Unless there is some understanding of the natural history of the cancers that are found — which are dangerous and which are not — the result can easily be more treatment of cancers that would not cause harm if left untreated, he said. 

“There may be some benefit to very early detection, but the costs will be huge — and I don’t mean monetary costs,” Dr. Berry said. “It’s possible that we all have cells that are cancerous and that grow a bit before being dumped by the body. ‘Hell bent for leather’ early detection research will lead to finding some of them. What will be the consequence? Prophylactic removal of organs in the masses? It’s really scary.”

But Dr. Laura Esserman, professor of surgery and radiology at the University of California, San Francisco, sees a real opportunity to figure out why some cancers go away.

“I am a breast cancer surgeon; I run a breast cancer program,” she said. “I treat women every day, and I promise you it’s a problem. Every time you tell a person they have cancer, their whole life runs before their eyes.

“What if I could say, ‘It’s not a real cancer, it will go away, don’t worry about it,’ ” she added. “That’s such a different message. Imagine how you would feel.”

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October 3, 2008, 11:33 am

What’s the Healthiest Diet of All?

By Peter Libby, M.D.

Diners at an outdoor cafe in Corsica, France. (Ed Alcock for The New York Times)

What exactly do doctors mean by a “healthy diet”?

Many of us consider the Mediterranean diet to be the closest thing known to an ideal meal plan, rich in vegetables, fruits, legumes, cereals, fish, olive oil and, yes, a bit of red wine with meals. Compared to traditional American menu — high in red meat and in butter and other dairy products — the Mediterranean diet is lower in saturated fat, more varied and often more satisfying.

Decades worth of research also suggests that this way of eating is healthier. Many studies have documented reduced rates of heart disease and cancer among those adhering to a Mediterranean diet, compared to those eating more red meat and dairy-based regimens. Most of these studies have involved observations rather than actual intervention trials, however, and they have varied in size.

Now the British Medical Journal has published a systematic compilation of a dozen of the most methodologically sound of these observational studies, which included over 1.5 million people followed for up to eighteen years, analyzing cardiovascular consequences and some other important health outcomes. This large meta-analysis found decreased cardiovascular death as well as cancer mortality, as well as a lowered incidence of Parkinson’s disease and Alzheimer’s disease, in those following the Mediterranean diet versus those on other diets.

While such meta-analyses have limitations and cannot be considered as persuasive as large, randomized intervention trials, the new study further supports the idea that the Mediterranean diet can confer important health benefits.

Different diets abound, many even promoted by physicians. But it’s a mistake to think of a diet as a temporary measure; instead, it is a lifetime commitment to healthy choices. Need to lose weight now? Don’t rush. Take comfort in knowing that even a modest incremental reduction can confer significant health benefits, lowering your risk of heart disease or diabetes. Crash diets only set us up “yo-yo” weight loss and regain.

Whatever eating habits you adopt must be sustainable over the long term. Many researchers regard this as the Mediterranean diet’s greatest strength. You can stick to it, and like it, year after year.

How sad, then, to learn that a diet that whose adherents were among the longest-lived in the world is now fading from view. The governments of Greece, Italy, Spain and Morocco have asked that UNESCO designate the Mediterranean diet an “intangible piece of cultural heritage.” But as The Times recently reported, fast food is proliferating across the Mediterranean region, threatening to propagate a U.S.-style obesity epidemic.

In Greece, three-quarters of the adult population is now overweight or obese, and at increasing risk for diabetes, heart disease and arthritis, among other maladies. “Much of the highly praised diet didn’t exist any more,” said a senior economist at the United Nations. ”It has become just a notion.” Rather than turning our backs on this traditional diet, the new data suggest we could all derive substantial health benefits from it.

[For some dishes with a Mediterranean flair, check out The Times' Recipes for Health. -- Eds.]

Living Longer, in Good Health to the End

By JANE E. BRODY

Published: August 25, 2008

You don’t have to be an actuary or funeral director to have noticed the striking increase in the length of many Americans’ lives. The obituaries in this or any other newspaper show a growing number of people who depart this world in their late 80s or 90s, or even at 100 or older.

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The fastest-growing segment of the population consists of people over 85, and by 2050 some 800,000 Americans will have celebrated their 100th birthday.

Doomsayers consider this a terrifying trend, bound to bankrupt Social Security and Medicare and overwhelm the ability of doctors and medical facilities to care for the burgeoning population of the oldest old.

But there is increasing evidence that the societal burden of increased longevity need not be so drastic. Long-term studies have shown that how people live accounts for more than half the difference in how hale and hearty they will remain until very near the end.

Many very old people have assumed “bragging rights” about their age and what they can still accomplish despite it, as Michael Kinsley wrote in The New Yorker in April.

At a pool in downtown Los Angeles, Mr. Kinsley encountered a stranger who interrupted his laps long enough to say, “I’m 90 years old.” The man, Richard Ibañez, a retired judge, died in November at age 97, but swam every morning until the last week of his life, his grandson, Christopher A. Karachale, wrote in a letter to the magazine.

A friend’s father, Irving Weinig, who lived in an assisted living facility in New York, requested new clothes for his 104th birthday so he could look spiffy when he had lunch with “the girls,” an activity he enjoyed until his death at 108.

And last spring the Island Nursing and Rehab Center in Holtsville, N.Y., boasted about a new resident, Nora Elizabeth Wright, who was turning 106.

All of these examples speak to a concept proposed in The New England Journal of Medicine in 1980 by Dr. James F. Fries of Stanford University: that adult vigor can be extended well into the ninth decade of life, with illness and disability compressed into a period that shortly precedes death.

Who Lives the Longest?

Many studies have examined the factors that predict the length of people’s lives, with nearly universal agreement that about 35 percent is determined by genes over which we have little or no control.

Dr. Nir Barzilai and colleagues at Albert Einstein College of Medicine found, for example, that individuals “with exceptional longevity” and a low incidence of age-related diseases have significantly larger HDL and LDL particles in their blood, a genetic characteristic that reduces their risk of developing cardiovascular diseases.

Scientists are searching for ways to extend healthy life spans by manipulating “bad” genes, but the potential exists now for modifying many of the environmental factors that account for the other 65 percent of longevity. And I suspect that most of us who hope to join the ranks of the oldest old would like to do so in a manner similar to that of Richard Ibañez and Irving Weinig — in rather good shape physically and mentally almost to the very end.

“Longevity is a Pyrrhic victory if those additional years are characterized by inexorable morbidity from chronic illness, frailty-associated disability and increasingly lowered quality of life,” Dr. William J. Hall of the Highland Hospital Center for Healthy Aging in Rochester wrote in The Archives of Internal Medicine in February.

New Habits Are Effective

Dr. Richard S. Rivlin, an internist and director of the nutrition and cancer prevention career development program at Weill Cornell Medical College, said in an interview that it was never too late to adopt habits that predict a healthy old age.

“While measures started early in life are most likely to have the greatest health benefit,” he said, “older people should never feel that turning over a new leaf at their age is anything but highly effective.”

He said there was clear evidence that measures taken in one’s 70s could help prevent “several important categories of disease, such as hypertension, heart disease, osteoporosis and even cancer.”

In The American Journal of Clinical Nutrition last year, Dr. Rivlin noted that changes in body composition, like loss of bone and muscle and accumulation of body fat, typically accompany aging and can affect health in a variety of ways: poor posture that impairs breathing; falls and fractures; loss of mobility; a reduced metabolic rate; and weight gain that can lead to diabetes, heart and blood vessel disease and some forms of cancer.

But these changes in body composition, he added, “are not an invariable accompaniment of aging.” Much can be done to limit and even reverse them, he said, including restricting calories and following a diet of high-quality protein and limited saturated fat and replacing simple sugars with whole grains rich in fiber.

The Importance of Exercise

A second critical measure for the “young-elderly,” as he calls 70-year-olds, is to “make regular exercise a part of their daily lifestyle,” including aerobic activities that raise the heart rate; weight-bearing activities that strengthen muscles and bones; and stretching exercises that reduce stiffness and improve flexibility and balance.

Another age-related concern is cognitive decline, which is more likely in people with metabolic syndrome, a cluster of modifiable risk factors that includes abdominal obesity, high blood pressure, insulin resistance and abnormal cholesterol levels. Dr. Hall cautioned against therapeutic nihilism in treating older people with such risk factors.

“Chronological age is a very imperfect determinant on which to base medical decision-making,” he wrote.

Dr. Hall’s comments were based on a 25-year study by Dr. Laurel B. Yates of Brigham and Women’s Hospital and her Boston colleagues of 2,357 men who were healthy at an average age of 72 when the study began. Of the 970 men who survived to at least age 90, the primary modifiable predictors of longevity were not smoking; preventing diabetes, obesity and high blood pressure; and exercising regularly.

“Compared with nonsurvivors, men with exceptional longevity had a healthier lifestyle, had a lower incidence of chronic diseases and were three to five years older at disease onset,” the Boston team reported in February in The Archives of Internal Medicine. “They had better late-life physical function and mental well-being. More than 68 percent rated their late-life health as excellent or very good, and less than 8 percent reported fair or poor health.”

Other long-term studies have also pinpointed exercise as the single most potent predictor of healthy longevity, in women as well as in men. It is not that very old people like Judge Ibañez can exercise because they are healthy, these findings indicate. Rather, they achieve a healthy old age because they exercise.

Studies Cast Doubt on Use of Calcium in Some Cases

By ANAHAD O'CONNOR

Published: April 28, 2005

espite what doctors have long recommended, regularly taking calcium and vitamin D does not prevent fractures in older people who have broken a bone or who have osteoporosis, according to two large studies released yesterday.

People with osteoporosis are often encouraged to consume as much calcium and vitamin D as possible to strengthen their bones and to lower the likelihood of injuries.

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But the new studies, involving thousands of elderly people in Britain who had symptoms of the disease, found that those who took calcium and vitamin D tablets were just as likely to break a bone as those who took neither.

The authors of the reports, published in The Lancet and the British medical journal BMJ, said their findings suggested that for people with brittle bones, relying solely on the supplements might not be enough.

"Our trial indicates that routine supplementation with calcium and vitamin D3, either alone or in combination, is not effective in the prevention of further fractures in people who have had a recent low-trauma fracture," the authors of the Lancet study wrote.

Other experts called the findings important but cautioned that they did not apply to most people.

Just people older than 70, a majority of them women with previous bone injuries, were included in the studies.

Because vitamin D and calcium are widely considered early preventive measures, it is no surprise that the studies failed to find them effective in people who already had osteoporosis or signs of it, said Dr. Steven R. Goldstein, a professor of obstetrics and gynecology at the New York University medical center.

"This is something we've known for a long time, that calcium and vitamin D alone are not enough to treat osteoporosis," Dr. Goldstein said. "Once you've developed frank osteoporosis and a bone fracture, you're going to need medication, not simply vitamin D and calcium to prevent fractures."

Osteoporosis causes bones to become thinner and occurs primarily in the elderly.

About 10 million Americans older than 50 develop the disease each year, and 1.5 million break bones because of it. Osteoporosis can be treated with drugs like biphosphonates that prevent the bones from deteriorating, but doctors often recommend taking supplements or eating foods rich in calcium and vitamin D to build up bone mass.

The largest of the two studies, in The Lancet, followed more than 5,o00 Scots who had broken bones in the last decade. Separated in four groups, the subjects received large doses of calcium, vitamin D, a combination of the two or a placebo. After several years, the researchers found that all four groups had roughly the same number of fractures, mostly to the hip.

Dr. Joan McGowan, an expert on osteoporosis at the National Institutes of Health, said it was surprising that there were not fewer fractures among the people who took the calcium and vitamin D, but that neither was seen a replacement for medication." Nobody thinks calcium and vitamin D are as potent as some of the other bone-active drugs that we have available," Dr. McGowan said.

Let the Sunshine in

By C. CLAIBORNE RAY

Published: April 15, 2008

Correction Appended

Q. Am I still getting vitamin D when I’m outside on a gray, cloudy day?

Victoria Roberts

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A. Just as it is possible to get a sunburn on an overcast day, it is possible to get the ultraviolet-B radiation needed for the skin to synthesize vitamin D even when skies are cloudy and gray. Efficiency varies, however, with the season, the altitude, skin color, the length of skin exposure and the percentage exposed, and air pollution.

Complete cloud cover halves the energy of ultraviolet rays, and shade reduces it by 60 percent, according to the National Institutes of Health.

The wavelengths of ultraviolet light needed to make vitamin D are from about 290 to 320 nanometers, within the ultraviolet-B range, which is also associated with sunburn and skin damage.

At the earth’s northern latitudes for much of the year, and at the midlatitudes in winter, the sun does not stay far enough above the horizon (45 degrees) for the angle of the sun’s rays to guarantee an efficient ultraviolet-B bath. Northerners may have to rely on the vitamin D synthesized in the summer or on foods and supplements.

Readers may submit questions by mail to Question, Science Times, The New York Times, 620 Eighth Avenue, New York, N.Y. 10018, or by e-mail to question@nytimes.com.

This article has been revised to reflect the following correction:

Correction: April 23, 2008
An answer in the Q&A column on April 15, about people getting vitamin D from exposure to the sun on a cloudy day, and a column on May 17, 2005, about getting the vitamin from exposure to sunlight through a window, incorrectly attributed a position to the National Institutes of Health about sun exposure and vitamin D. The columns also referred to an outdated fact sheet posted on the N.I.H. Web site. The recommendation for 10 to 15 minutes of exposure twice a week is the view of an author cited by the institutes; the N.I.H. itself makes no recommendation on sun exposure. An updated fact sheet on the topic can be found at http://dietary-supplements.info.nih.gov/factsheets.

An Oldie Vies for Nutrient of the Decade

By JANE E. BRODY

Published: February 19, 2008

The so-called sunshine vitamin is poised to become the nutrient of the decade, if a host of recent findings are to be believed. Vitamin D, an essential nutrient found in a limited number of foods, has long been renowned for its role in creating strong bones, which is why it is added to milk.

Stuart Bradford

Now a growing legion of medical researchers have raised strong doubts about the adequacy of currently recommended levels of intake, from birth through the sunset years. The researchers maintain, based on a plethora of studies, that vitamin D levels considered adequate to prevent bone malformations like rickets in children are not optimal to counter a host of serious ailments that are now linked to low vitamin D levels.

To be sure, not all medical experts are convinced of the need for or the desirability of raising the amount of vitamin D people should receive, either through sunlight, foods, supplements or all three. The federal committee that establishes daily recommended levels of nutrients has resisted all efforts to increase vitamin D intake significantly, partly because the members are not convinced of assertions for its health-promoting potential and partly because of time-worn fears of toxicity.

This column will present the facts as currently known, but be forewarned. In the end, you will have to decide for yourself how much of this vital nutrient to consume each and every day and how to obtain it.

Where to Obtain It

Through most of human history, sunlight was the primary source of vitamin D, which is formed in skin exposed to ultraviolet B radiation (the UV light that causes sunburns). Thus, to determine how much vitamin D is needed from food and supplements, take into account factors like skin color, where you live, time of year, time spent out of doors, use of sunscreens and coverups and age.

Sun avoiders and dark-skinned people absorb less UV radiation. People in the northern two-thirds of the country make little or no vitamin D in winter, and older people make less vitamin D in their skin and are less able to convert it into the hormone that the body uses. In addition, babies fed just breast milk consume little vitamin D unless given a supplement.

In addition to fortified drinks like milk, soy milk and some juices, the limited number of vitamin D food sources include oily fish like salmon, mackerel, bluefish, catfish, sardines and tuna, as well as cod liver oil and fish oils. The amount of vitamin D in breakfast cereals is minimal at best. As for supplements, vitamin D is found in prenatal vitamins, multivitamins, calcium-vitamin D combinations and plain vitamin D. Check the label, and select brands that contain vitamin D3, or cholecalciferol. D2, or ergocalciferol, is 25 percent less effective.

Vitamin D content is listed on labels in international units (I.U.). An eight-ounce glass of milk or fortified orange juice is supposed to contain 100 I.U. Most brands of multivitamins provide 400 a day. Half a cup of canned red salmon has about 940, and three ounces of cooked catfish about 570.

Myriad Links to Health

Let’s start with the least controversial role of vitamin D — strong bones. Last year, a 15-member team of nutrition experts noted in The American Journal of Clinical Nutrition that “randomized trials using the currently recommended intakes of 400 I.U. vitamin D a day have shown no appreciable reduction in fracture risk.”

“In contrast,” the experts continued, “trials using 700 to 800 I.U. found less fracture incidence, with and without supplemental calcium. This change may result from both improved bone health and reduction in falls due to greater muscle strength.”

A Swiss study of women in their 80s found greater leg strength and half as many falls among those who took 800 I.U. of vitamin D a day for three months along with 1,200 milligrams of calcium, compared with women who took just calcium. Greater strength and better balance have been found in older people with high blood levels of vitamin D.

In animal studies, vitamin D has strikingly reduced tumor growth, and a large number of observational studies in people have linked low vitamin D levels to an increased risk of cancer, including cancers of the breast, rectum, ovary, prostate, stomach, bladder, esophagus, kidney, lung, pancreas and uterus, as well as Hodgkin’s lymphoma and multiple myeloma.

Researchers at Creighton University in Omaha conducted a double-blind, randomized, placebo-controlled trial (the most reliable form of clinical research) among 1,179 community-living, healthy postmenopausal women. They reported last year in The American Journal of Clinical Nutrition that over the course of four years, those taking calcium and 1,100 I.U. of vitamin D3 each day developed about 80 percent fewer cancers than those who took just calcium or a placebo.

Vitamin D seems to dampen an overactive immune system. The incidence of autoimmune diseases like Type 1 diabetes and multiple sclerosis has been linked to low levels of vitamin D. A study published on Dec. 20, 2006, in The Journal of the American Medical Association examined the risk of developing multiple sclerosis among more than seven million military recruits followed for up to 12 years. Among whites, but not blacks or Hispanics, the risk of developing M.S. increased with ever lower levels of vitamin D in their blood serum before age 20.

A study published in Neurology in 2004 found a 40 percent lower risk of M.S. in women who took at least 400 I.U. of vitamin D a day.

Likewise, a study of a national sample of non-Hispanic whites found a 75 percent lower risk of diabetes among those with the highest blood levels of vitamin D.

Vitamin D is a fat-soluble vitamin that when consumed or made in the skin can be stored in body fat. In summer, as little as five minutes of sun a day on unprotected hands and face can replete the body’s supply. Any excess can be stored for later use. But for most people during the rest of the year, the body needs dietary help.

Furthermore, the general increase in obesity has introduced a worrisome factor, the tendency for body fat to hold on to vitamin D, thus reducing its overall availability.

As for a maximum safe dose, researchers like Bruce W. Hollis, a pediatric nutritionist at the Medical University of South Carolina in Charleston, maintain that the current top level of 2,000 I.U. is based on shaky evidence indeed — a study of six patients in India. Dr. Hollis has been giving pregnant women 4,000 I.U. a day, and nursing women 6,000, with no adverse effects. Other experts, however, are concerned that high vitamin D levels (above 800 I.U.) with calcium can raise the risk of kidney stones in susceptible people.

Nutrition: Vitamin D May Play Larger Role in Health

By ERIC NAGOURNEY

Published: August 18, 2008

A lack of vitamin D has been found in some studies to play an unrecognized role in death among people suffering from a variety of medical problems, including heart disease and cancer.

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Now researchers say they have evidence that even in the general population, having too little of the vitamin appears to be associated with a higher risk of death.

Writing in The Archives of Internal Medicine, researchers say they looked at the vitamin D levels and death rates of more than 13,000 people over a period of more than six years.

Those who fell in the lowest quarter of vitamin D levels had a 26 percent higher risk of death from all causes than those in the top quarter, found the study, which was led by Dr. Michal L. Melamed of the Albert Einstein College of Medicine.

About 41 percent of men and 53 percent of women in the United States have levels of the vitamin that are considered too low.

The researchers pointed to other studies looking at the role in disease of vitamin D, which can be found in milk and also comes from exposure to the sun. Researchers have found, for example, that deaths from cardiovascular disease are higher in the winter, when less sun leads to lower levels of vitamin D.

The question now, the study says, is whether taking supplements to raise levels of the vitamin would lower the risk of death.

PERSONAL HEALTH; A Second Opinion on Sunshine: It Can Be Good Medicine After All

June 17, 2003

By JANE E. BRODY

Can sunshine, now shunned by so many who fear skin cancer and wrinkles, save many more lives than it harms? Most definitely, says a leading expert in the field, Dr. Michael F. Holick, a professor of medicine, dermatology, physiology and biophysics at the Boston University School of Medicine.

Dr. Holick, who discovered the active form of vitamin D, has pulled together an impressive body of evidence in support of his advice that no one should be, as he puts it, a ''sunphobe'' or, for that matter, a sun worshiper.

He has concluded that relatively brief but unfettered exposure to sunshine or its equivalent several times a week can help to ward off a host of debilitating and sometimes deadly diseases, including osteoporosis, hypertension, diabetes, multiple sclerosis, rheumatoid arthritis, depression and cancers of the colon, prostate and breast.

In other words, Dr. Holick says, sunshine is good medicine.

But like all medicines, the right dosage is critical to reaping the rewards that sunlight has to offer without suffering unwanted consequences.

Dr. Holick elaborates on these research-based ideas in a small but important book, ''The UV Advantage,'' written with Mark Jenkins, a health writer. Though originally scheduled for publication next month, the book fell victim to a publishing world shake-up and will not come out until the fall or winter.

But given the arrival of the sunshine season, people should have the opportunity to benefit from the doctor's insights without further delay.

A Ubiquitous Hormone

Dr. Holick's argument that controlled exposure to sunshine can have powerful health benefits stems from decades of research into the many roles played by vitamin D in the body. The main source of this essential nutrient is neither food nor dietary supplement. It is sunshine.

Vitamin D is made in the skin when it is exposed to the ultraviolet B (UVB) rays in sunshine, as well as those from tanning machines. But the amount of vitamin D formed in a given period of sun exposure depends on the color of that skin -- that is, how rich the skin is in melanin, which blocks UV rays.

The darker a person's skin, the longer he or she has to be in sun to form a significant amount of vitamin D.

A national study showed that 42 percent of African-American women ages 15 to 49 were deficient in vitamin D by the end of winter. A very dark-skinned person may need to spend up to 50 times as much time in the sun to make the same amount of vitamin D as someone of Scandinavian descent. For the average African-American, 5 to 10 times as much time in the sun will be needed.

Another critical factor is where a person lives in relation to the Equator. The farther away, the less intense one's exposure to UVB rays. This is undoubtedly why people in northern latitudes evolved with light skin, to enhance their ability to absorb UVB rays, and those near the Equator evolved with very dark skin, to limit that absorption to a physiologically desirable amount.

For vitamin D to perform its myriad biochemical roles in body cells, it must first be converted into an activated form, vitamin D hormone. For years it was thought that this process took place only in the kidneys, which then sent tiny amounts of the hormone to the circulatory system for delivery to other tissues.

But studies by Dr. Holick and others have shown that the cells in many different organs do not have to rely on the meager supply of vitamin D hormone from the kidneys. Rather, cells in other tissues, including the prostate, breast, colon and immune system, are also able to convert vitamin D into the active hormone.

Many Health Effects

Everyone should know that vitamin D is critical to the formation and maintenance of normal bones. Even if people consume enough calcium, they cannot build and maintain bone mass if they are deficient in vitamin D. One symptom of vitamin D deficiency is pain and weakness in the muscles and bones. Based on that symptom, Dr. Holick has suggested that some disorders diagnosed as fibromyalgia may in fact be vitamin D deficiency.

Dr. Holick noted a recent resurgence of rickets in the United States, the combined result of exclusive breast-feeding (breast milk has almost no vitamin D) and keeping babies out of the sun or slathered with sunscreen.

A sunscreen with an S.P.F. of 8 blocks 95 percent of the skin's ability to make vitamin D, and an S.P.F. of 15 blocks it by 99 percent.

In the prostate, the vitamin D hormone has been shown to act as a powerful inhibitor of abnormal cell growth, and cells in the colon and breast have similar mechanisms for using this hormone.

A Scandinavian study linked low levels of vitamin D in the blood to a risk of developing prostate cancer that is about 50 percent higher than it is for those with normal and high levels. And in eight years of research conducted in an aging study in Baltimore, experts found that those with low levels of circulating vitamin D had a 50 percent greater risk of developing colon cancer than those with normal to high levels.

Dr. William Grant of the National Aeronautics and Space Administration reported that people who worked outdoors or lived in sunny climates had lower death rates from cancers of the breast, colon, prostate, ovary, bladder, uterus, esophagus, rectum and stomach.

Dr. Grant calculated that 85,000 fewer cases of cancer and 30,000 fewer cancer deaths would occur each year if everyone got as much sun as people living in the Southwest.

The same applies to autoimmune diseases like multiple sclerosis, rheumatoid arthritis and Type 1 diabetes, which is usually diagnosed in children and young adults.

Dr. Holick, meanwhile, has found that exposing people with high blood pressure to UVB rays in a tanning salon lowers their blood pressure readings about as much as a drug will. He also found that increasing vitamin D improved the heart's pumping ability and reduced cardiac strain.

Safe in the Sun

How much vitamin D is enough? Although the official recommended amount ranges from 200 international units for infants to 600 for the elderly, Dr. Holick and other experts say 1,000 units a day are needed, an amount few people consume through foods or supplements. Sunshine must fill in the gap.

''Between 90 percent and 95 percent of most people's vitamin D comes from casual exposure to sunlight,'' Dr. Holick said. He does not advocate tanning. Rather, he proposes exposing unprotected skin to sunlight for a matter of minutes, with the recommended time determined by a person's skin type, the time of year, the time of day and the latitude.

He suggests figuring out how long it takes for one's skin to turn pink in the sun (not burned, just pink) and then exposing a quarter of one's body (e.g., hands, arms and face or, if not the face, then the arms and legs) to the sun for one quarter of that time. After that, if a person plans to remain outdoors, the advice is to cover up or apply sunscreen that blocks both UVA and UVB rays.

For example, a person with Skin Type 2 (characteristic of most Caucasians) that burns easily and hardly tans who lives in the northern half of the country might expose a quarter of the body surface to the sun for 5 to 10 minutes a day between 11 a.m. and 3 p.m. during the next five months to build up enough vitamin D to last through the winter.

Vitamin D Deficiency May Lurk in Babies

By RONI CARYN RABIN

Published: August 25, 2008

Until she was 11 months old, Aleanie Remy-Marquez could have starred in an advertisement for breast milk. She took to nursing easily, was breast-fed exclusively for six or seven months, and ate little else even after that. She was alert and precocious and developed at astonishing speed, her mother said, sitting at four months and walking by eight months.

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But once Aleanie started putting weight on her feet, her mother noticed that her legs were curving in a bow shape below the knees. Doctors diagnosed vitamin D-deficiency rickets, a softening of the bones that develops when children do not get enough vitamin D — a crucial ingredient for absorbing calcium and building bone, and the one critical hormone that breast milk often cannot provide enough of.

“I thought I was doing the best thing for her,” said Stephanie Remy-Marquez, of Hyde Park, Mass., after blood tests showed her daughter had no detectable vitamin D. X-ray images of the baby’s wrists and knees showed the edges of the bones and growth plates as blurry and fraying instead of crisp and sharp.

“Breast milk is supposed to be an entire meal, dessert and drinks included,” Ms. Remy-Marquez said. “I thought it was the ultimate cocktail.”

Aleanie’s case was unusual enough to be written up in the journal Clinical Pediatrics in May, but several similar reports have been published in recent years. Some experts fear that vitamin D deficiency, which can be asymptomatic, may be more common than pediatricians realize and that rickets — perceived to be a 19th-century scourge that was wiped out with the fortification of milk — may be going undetected.

Physicians have known for more than a century that exclusive breast-feeding may be associated with vitamin D deficiency and rickets, and that the condition is easily prevented and treated with inexpensive vitamin drops or cod liver oil. But doctors are reluctant to say anything that might discourage breast-feeding.

Now some researchers are also linking vitamin D deficiency with other chronic diseases like diabetes, autoimmune disorders and even cancer, and there have been calls to include blood tests of vitamin D levels in routine checkups.

“I completely support breast-feeding, and I think breast milk is the perfect food, and the healthiest way to nourish an infant,” said Dr. Catherine M. Gordon, director of the bone health program at Children’s Hospital Boston and an author of several studies on vitamin D deficiency, including Aleanie’s case.

“However,” Dr. Gordon continued, “we’re finding so many mothers are vitamin D deficient themselves that the milk is therefore deficient, so many babies can’t keep their levels up. They may start their lives vitamin D deficient, and then all they’re getting is vitamin D deficient breast milk.”

Some doctors and public health officials say conditions may be ripe for rickets to re-emerge: more infants are being breast-fed for extended periods, children are drinking more juice or soda and less milk, and they are spending less time exposed to sunlight, which enables the skin to synthesize vitamin D.

Children with dark skin, like Aleanie, who is African-American, appear to be at even greater risk for rickets because they do not synthesize vitamin D through the skin as easily as those with light skin.

The solution, Dr. Gordon said, is not to quit breast-feeding but to supplement breast-fed infants with vitamin drops, as recommended by the American Academy of Pediatrics. The academy issued guidelines in 2003 recommending that infants be given 200 international units of vitamin D daily, and it may be increasing the recommended level soon.

But pediatricians do not consistently prescribe vitamin drops. A 2004 survey of North Carolina pediatricians found that fewer than half routinely recommended them, and one in six never recommended them.

Vitamin D deficiency may not be immediately apparent, even as it affects growth, muscle and bone mineralization, said Dr. Craig Langman, professor of kidney disease and pediatrics at Feinberg School of Medicine in Chicago.

“It sort of sneaks up on you,” he said. “So the worst scenario is the gas tank is empty and the car won’t go — you have rickets. But at very low levels of gas the car doesn’t perform very well and you start having intermittent loss of power and that sort of thing; as a result you may not be forming enough bone during childhood.”

A recent review of 14 studies, done by researchers at the National Institute of Child Health and Human Development and published in The Archives of Pediatrics & Adolescent Medicine in June, found that extreme vitamin D deficiency was rare in the United States, but that up to 78 percent of breast-fed babies who were not supplemented in wintertime were deficient.

Meanwhile, the number of papers describing cases of nutritional rickets in babies and young children in the United States has been accumulating over the past decade or so, from places as disparate as Alaska, Minnesota, Nevada and Texas.

The patients are more likely to be African-American and dark-skinned, and more likely to have been exclusively breast-fed for an extended period of time, without vitamin supplementation. Rates are often higher when there is less sunlight.

In a study conducted by Dr. Gordon of vitamin D levels in 365 mostly African-American and Latino infants and toddlers, 40 percent had low levels and 12 percent were deficient. Although there is a debate about what levels are considered deficient, one toddler in the study was found to have rickets, 13 children showed evidence of bone loss and 3 had bone changes consistent with rickets.

The study, published in The Archives of Pediatrics & Adolescent Medicine in June, found that breast-feeding without supplementation was a significant risk factor.

“Human milk is very low in vitamin D, absolutely — there is no question about that,” said Dr. Frank Greer, professor of pediatrics at University of Wisconsin School of Medicine and Public Health and chairman of the committee on nutrition of the American Academy of Pediatrics. “Historically speaking, we probably got it from the sun, but now we’re afraid of the sun and we don’t go out as much.”

Teenagers are also at risk for vitamin D deficiency. Although their large bones protect them against rickets, they are at risk for osteopenia and even osteoporosis, and may have weaker bones that are more likely to fracture, said Dr. Robert Schwartz, professor of pediatrics at Wake Forest University Baptist Medical Center in Winston-Salem, N.C., who said he had observed cases of osteopenia and osteoporosis in teenagers.

“The tragedy of this is that when they’re young, they’re building up bone for the rest of their life,” Dr. Schwartz said. As people age and their bones weaken, he said: “Those who had adequate vitamin D and calcium will slide down from the top of the mountain. These kids will slide down from the middle.”

The Well column will return next week.

More Articles in Health » A version of this article appeared in print on August 26, 2008, on page F5 of the New York edition.

Better to Be Fat and Fit Than Skinny and Unfit

Stuart Bradford

By TARA PARKER-POPE

Published: August 18, 2008

Often, a visit to the doctor’s office starts with a weigh-in. But is a person’s weight really a reliable indicator of overall health?

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Increasingly, medical research is showing that it isn’t. Despite concerns about an obesity epidemic, there is growing evidence that our obsession about weight as a primary measure of health may be misguided.

Last week a report in The Archives of Internal Medicine compared weight and cardiovascular risk factors among a representative sample of more than 5,400 adults. The data suggest that half of overweight people and one-third of obese people are “metabolically healthy.” That means that despite their excess pounds, many overweight and obese adults have healthy levels of “good” cholesterol, blood pressure, blood glucose and other risks for heart disease.

At the same time, about one out of four slim people — those who fall into the “healthy” weight range — actually have at least two cardiovascular risk factors typically associated with obesity, the study showed.

To be sure, being overweight or obese is linked with numerous health problems, and even in the most recent research, obese people were more likely to have two or more cardiovascular risk factors than slim people. But researchers say it is the proportion of overweight and obese people who are metabolically healthy that is so surprising.

“We use ‘overweight’ almost indiscriminately sometimes,” said MaryFran Sowers, a co-author of the study and professor of epidemiology at the University of Michigan. “But there is lots of individual variation within that, and we need to be cognizant of that as we think about what our health messages should be.”

The data follow a report last fall from researchers at the Centers for Disease Control and Prevention and the National Cancer Institute showing that overweight people appear to have longer life expectancies than so-called normal weight adults.

But many people resist the notion that people who are overweight or obese can be healthy. Several prominent health researchers have criticized the findings from the C.D.C. researchers as misleading, noting that mortality statistics don’t reflect the poor quality of life and suffering obesity can cause. And on the Internet, various blog posters, including readers of the Times’s Well blog, have argued that the data are deceptive, masking the fact that far more overweight and obese people are at higher cardiovascular risk than thin people.

Part of the problem may be our skewed perception of what it means to be overweight. Typically, a person is judged to be of normal weight based on body mass index, or B.M.I., which measures weight relative to height. A normal B.M.I. ranges from 18.5 to 25. Once B.M.I. reaches 25, a person is viewed as overweight. Thirty or higher is considered obese.

“People get confused by the words and the mental image they get,” said Katherine Flegal, senior research scientist at the C.D.C.’s National Center for Health Statistics. “People may think, ‘How could it be that a person who is so huge wouldn’t have health problems?’ But people with B.M.I.’s of 25 are pretty unremarkable.”

Several studies from researchers at the Cooper Institute in Dallas have shown that fitness — determined by how a person performs on a treadmill — is a far better indicator of health than body mass index. In several studies, the researchers have shown that people who are fat but can still keep up on treadmill tests have much lower heart risk than people who are slim and unfit.

In December, a study in The Journal of the American Medical Association looked at death rates among 2,600 adults 60 and older over 12 years. Notably, death rates among the overweight, those with a B.M.I. of 25 to 30, were slightly lower than in normal weight adults. Death rates were highest among those with a B.M.I. of 35 or more.

But the most striking finding was that fitness level, regardless of body mass index, was the strongest predictor of mortality risk. Those with the lowest level of fitness, as measured on treadmill tests, were four times as likely to die during the 12-year study than those with the highest level of fitness. Even those who had just a minimal level of fitness had half the risk of dying compared with those who were least fit.

During the test, the treadmill moved at a brisk walking pace as the grade increased each minute. In the study, it didn’t take much to qualify as fit. For men, it meant staying on the treadmill at least 8 minutes; for women, 5.5 minutes. The people who fell below those levels, whether fat or thin, were at highest risk.

The results were adjusted to control for age, smoking and underlying heart problems and still showed that fitness, not weight, was most important in predicting mortality risk.

Stephen Blair, a co-author of the study and a professor at the Arnold School of Public Health at the University of South Carolina, said the lesson he took from the study was that instead of focusing only on weight loss, doctors should be talking to all patients about the value of physical activity, regardless of body size.

“Why is it such a stretch of the imagination,” he said, “to consider that someone overweight or obese might actually be healthy and fit?”

well@nytimes.com