Does Vitamin E Prevent Breast Cancer?May 2002
By Dr. Michele Morrow, Board Certified Physician
Since one out of every eight women is destined to develop breast cancer,1 a tremendous amount of research has been undertaken to discover ways of preventing this common killer. One compound that has been extensively studied for its role in preventing breast cancer is vitamin E.
Up until now, however, no one has compiled and analyzed the large volume of published data about vitamin E and breast cancer. A researcher at Wake Forest University School of Medicine took on this enormous task and her comprehensive work was just published in the Journal of Nutritional Biochemistry.2
If you take vitamin E supplements, this eye-opening report reveals startling findings about what forms of vitamin E may be effective, which women are most likely to benefit, and a form of vitamin E that certain women should avoid.
As a prelude to this article, readers should know that emerging evidence is calling into question previously held concepts about how vitamins function in the body. While this new information corroborates what has been earlier cited in this publication, it is nonetheless critical to remind readers of the need to keep up with current findings. For women concerned about breast cancer, there now appear to be validated methods of reducing the risk if the proper forms of vitamin E are consumed.
Some people believe that vitamin E reduces breast cancer risk because of reports showing that severely deficient women suffer far higher rates of breast cancer.
Several studies, for instance, show that premenopausal women with very low intakes of vitamin E are twice as likely to contract breast cancer compared to women who come close to meeting the minimum requirements. This statistic is relatively useless, however, since it was women who consumed less than 7 mg a day who were at a 50% greater risk of contracting breast cancer.3-7 Other studies show no risk reduction in women obtaining greater than 8 mg a day of vitamin E.8,9
Since supplement users take 400 mg or more a day of vitamin E, everyone wants to know how much reduction in breast cancer incidence can be expected when potencies of 400 mg (400 IU) and higher are consumed.
Studies on total vitamin E intake show that women with a family history of breast cancer may derive an 80% risk reduction, whereas women who don't have a family history obtain a 60% risk reduction.5 The risk reduction, however, is not consistent amongst different groups of women. When subsequent analyses of this data was conducted, more definitive information was obtained.5 The chart on the upper right shows different categories of women and the specific risk reduction effect from foods that are high in vitamin E.
Controlled studies on alpha tocopherol
The Nurses Health Study studied 83,234 women at baseline and sought to assess incidences of breast cancer during a 14 year follow-up. This study showed that premenopausal women with a family history who consumed the highest quantity of vitamin E enjoyed a 43% reduction in breast cancer incidence compared to only a 16% risk reduction for women without a family history of breast cancer.11 Based on this study, vitamin E appears to protect against genetic- predisposed breast cancer better than environmental-induced breast cancer. (Note that nutrients like indole-3-carbinol may specifically protect against environmental breast carcinogens.)
Several studies reviewed the effects of standard vitamin E products (alpha tocopherol acetate) taken by themselves. The results fail to show a protective benefit, even when high doses of these alpha tocopherol supplements are consumed.7,11-15 This indicates that other forms of vitamin E found in food (such as gamma tocopherol and tocotrienols) may be responsible for providing the dramatic protective effect against breast cancer shown in surveys that evaluate total vitamin E intake.
Another method that scientists have used to ascertain vitamin E's potential benefit is to measure frozen blood levels of vitamin E and then follow up to see how many women subsequently develop breast cancer. One study of postmenopausal women showed a modest 20% reduction in breast cancer risk in the highest quartile of serum vitamin E (alpha tocopherol) compared to the lowest.16 Other studies based on measuring alpha tocopherol from stored blood serum do not show a protective effect.17,18
Some doctors believe the best way of determining vitamin E status is to test breast adipose (fat) tissue for vitamin E concentration in healthy controls as opposed to newly diagnosed breast cancer patients. One compelling study showed that newly diagnosed breast cancer patients had six times less vitamin E in their breast tissue compared to women without breast cancer.19 The major flaw to this study was that the control group was nine years younger on average than the breast cancer patients and other confounding factors were not accounted for. Other studies seeking to assess adipose concentrations of vitamin E in breast cancer patients are inconclusive. 20,21
Taken together, the results of the studies presented indicate that certain vitamin E fractions found in food confer a significant protective effect, but that commercial alpha tocopherol acetate supplements fail to reduce breast cancer incidence for most women. The data indicate that some other vitamin E component in food may account for the dramatic reductions in breast cancer incidence (as much as 90%) when dietary intake levels of vitamin E are measured.
(Note: 400 mg of vitamin E succinate provides 400 IU of vitamin E activity whereas 400 mg of vitamin E acetate typically provides 200 IU of vitamin E activity.)