Almost half of all adults in the U.S. take supplements daily, but the studies should prompt some of them to reconsider their rationale for doing so, one expert says.
By Karen Kaplan
Vitamin supplements — taken by millions of Americans to boost or maintain their health — don’t reduce the risk of heart attacks, strokes or breast cancer, according to two large studies published today.
In one of the trials, 14,641 middle-aged male physicians took vitamins E and C for an average of eight years but did not see any benefit to their cardiovascular health.
The other study tracked 36,282 postmenopausal women for an average of seven years and found that a daily regimen of vitamin D and calcium did not offer any protection against invasive breast cancer.
Almost half of all adults in the U.S. take vitamins daily, but the results should prompt some of them to reconsider their rationale for doing so, said Howard Sesso, who led the cardiovascular disease study appearing in the Journal of the American Medical Assn.
"You don’t know whether something is really true until you test it in one of these large-scale, long-term clinical trials," said Sesso, an epidemiologist at Brigham and Women’s Hospital in Boston and a professor at Harvard Medical School.
But Dr. David Heber, director of the UCLA Center for Human Nutrition, said the studies didn’t prove vitamins were useless, especially considering that observational studies and experiments with animals had produced mixed results.
"Absence of evidence is not evidence of absence," said Heber, who was not involved with the latest studies.
The heart study was prompted by basic research showing that antioxidants such as vitamins E and C kept the formation of atheroschlerotic plaque in check and helped prevent tissue damage that causes cardiovascular disease.
Sesso’s team tested the effect of 400 international units, or IUs, of vitamin E every other day and 500 milligrams of vitamin C daily. Doctors who participated in the study received either both vitamins, one vitamin and one placebo, or two placebos.
Among the 7,315 people who took vitamin E, there were 620 cases of heart attacks, strokes and deaths from heart disease compared with 625 such cases among the 7,326 people who took the dummy pills, the study said.
The only difference the researchers found was a 74% increase in hemorrhagic strokes among those who took vitamin E, though Sesso said that the strokes were rare in both groups and that the finding could have been a fluke.
The results for vitamin C were also underwhelming — 619 major cardiovascular events among the 7,329 doctors who got the vitamin versus 626 events for the 7,312 who got the placebo, according to the study, which was funded by the National Institutes of Health and BASF Corp., a vitamin maker.
The breast cancer study, reported in the Journal of the National Cancer Institute, was part of an effort to determine whether a combined pill of 1,000 milligrams of calcium and 400 IUs of vitamin D could help prevent hip fractures.
Since some studies suggested vitamin D might reduce the risk of breast cancer, the researchers, led by Dr. Rowan Chlebowski, a medical oncologist at the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, decided to track that too.
Over the course of the study, 528 of the 18,176 women, or 2.9%, who got the combined pill developed invasive breast cancer compared with 546 of the 18,106 who got the placebo, or 3.0%.
In an editorial accompanying the study, Corey Speers and Dr. Powel Brown of the Baylor College of Medicine in Houston praised the research for its "scope and complexity" but said it did not rule out a benefit from vitamin D.
Other studies suggest the daily dose should be between 1,000 and 2,000 IUs per day, well above the amount used in this trial.
The supplements might also prove valuable to premenopausal women, who were not part of this study, they said.
Chlebowski, whose study was also funded by the NIH, cautioned that women shouldn’t stop taking vitamin D based on his results.
"Take it anyway, for other reasons," he said.
Kaplan is a Times staff writer.