Vitamin E supplements do not protect healthy women against heart attacks and stroke, according to new results from the Women's Health Study, a long-term clinical trial of the effect of vitamin E and aspirin on both the prevention of cardiovascular disease and of cancer.
The vitamin E results of the Women's Health Study are published in the July 6 issue of the Journal of the American Medical Association. In addition to the cardiovascular disease findings, the study authors report that there was no effect of vitamin E on total cancer or on the most common cancers in women - breast, lung, and colon cancers. The Women's Health Study was funded by the National Heart, Lung, and Blood Institute (NHLBI) and the National Cancer Institute of the National Institutes of Health.
"This landmark trial has given women and their physicians important health information. We can now say that despite their initial promise, vitamin E supplements do not prevent heart attack and stroke. Instead, women should focus on well proven means of heart disease prevention, including leading a healthy lifestyle and controlling risk factors such as high blood pressure and high cholesterol," said NHLBI Director Elizabeth G. Nabel, M.D.
The Women's Health Study was conducted between 1992 and 2004. The participants were 39,876 healthy women age 45 years and older who were randomly assigned to receive 600 IU of Vitamin E or placebo and low-dose aspirin or placebo on alternate days. The participants were followed for an average of 10.1 years. The aspirin results published last March found no benefit of aspirin (100 mg every other day) in preventing first heart attacks or death from cardiovascular causes in women but did find a reduced risk of stroke overall, as well as reduced risk of both stroke and heart attack in women aged 65 and older.
In recent years, there has been a great deal of public and scientific interest in the potential of antioxidant vitamins like vitamin E to reduce the risk of cardiovascular disease. Laboratory and animal research suggested that vitamin E might prevent the accumulation of fatty deposits inside arteries, which would reduce the chance of clogged and blocked arteries. Other large observational studies have also suggested that people who eat foods high in vitamin E or take supplements have a lower risk of coronary heart disease. Although several clinical trials conducted prior to the Women's Health study found little cardiovascular benefit from vitamin E, these trials were shorter and primarily studied individuals with cardiovascular disease or CVD risk factors. The intent of the Women's Health Study was to provide a long-term look at the effects of vitamin E supplementation among healthy women.
Participants in the Women's Health Study were monitored for major cardiovascular "events" - a combination of nonfatal heart attack, nonfatal stroke, or cardiovascular death. By the end of the study, participants in the vitamin E group had 482 such events compared to 517 in the placebo group. However, this difference was not statistically different.
For the individual cardiovascular events, the study findings were:
- Nonfatal heart attacks: 184 in the vitamin E group versus 181 in the placebo group -- not a statistically significant difference.
- Nonfatal strokes: 220 in the vitamin E group versus 222 in the placebo group -- not statistically significant.
Study investigators also found no significant effect of vitamin E on total deaths (deaths from all causes). By the end of the study, there were 636 deaths in the vitamin E group compared to 615 in the placebo group.
Although total deaths were unaffected by vitamin E, there was a significant 24 percent reduction in cardiovascular deaths among all women taking the vitamin (106 deaths in the vitamin E group versus 140 in the placebo group). In another positive finding, women 65 and older taking vitamin E had a 26 percent decrease in heart attacks and cardiovascular deaths, but not strokes.
"These intriguing findings deserve further study. But they were not part of the primary aim of the study -- to look at the effect of vitamin E on overall cardiovascular disease, which includes heart attack, stroke, and cardiovascular death. Additionally, previous studies of vitamin E in patients with heart disease have not shown any benefit for cardiovascular deaths. At present, we cannot recommend vitamin E for prevention against cardiovascular disease or cancer," said lead investigator I-Min Lee, MBBS, ScD of Brigham and Women's Hospital.
The study finding of a decrease in major cardiovascular events among women age 65 years and older is relatively unique, added Dr. Lee. "Almost all previous trials have not reported findings by age. If other current trials provide age-related results, these additional data will help clarify the Women's Health Study results of benefit among the women aged 65 years and older," she said.
Overall, the results were not affected by a study participant's menopausal status, use of hormone therapy, body mass index, alcohol intake, or physical activity. The study found no significant side effects among women taking vitamin E except for an increase in nosebleeds, which was likely due to chance, as there was no increase in risk of other types of bleeding, including hemorrhagic stroke.
According to the 1999-2000 National Health and Nutrition Examination Survey, an estimated 13.5 percent of women in the U.S. take vitamin E supplements, although it is not known how many are taking the vitamin to prevent heart disease and stroke.
NHLBI's Dr. Nabel encouraged women to learn more about proven ways to prevent heart disease, the number one killer of women. The Heart Truth (www.hearttruth.gov), NHLBI's program to increase women's awareness of the dangers of heart disease, offers resources and information on leading a healthy lifestyle.
To interview an NHLBI spokesperson about the Women's Health Study findings, contact the NHLBI Communications Office at (301) 496-4236. To interview a study investigator, contact Melanie Franco or Lori Shanks at Brigham and Women's Hospital at (617) 534-1600.