Vitamin B May Reduce Women's Breast Cancer Risk
High levels of vitamin B may protect women against breast cancer, the most common non-skin cancer among U.S. women, according to a study in the March 5 Journal of the National Cancer Institute.
Researchers measured levels of folate, a type of B vitamin, in more than 1,400 women. They found that those in the top fifth had a 27 percent lower risk of breast cancer than women with the lowest folate levels. Vitamin B12 may also protect premenopausal women against tumors, the study suggested.
The trial is the first to gauge risk based on direct measurements of B vitamins. It reinforces the importance of eating leafy vegetables and taking vitamin B supplements, study leader Shumin Zhang said in an interview.
``We encourage women to get adequate amounts of folate from food, but taking a supplement is probably good insurance that you will get high enough levels,' said Zhang, an epidemiologist at Brigham and Women's Hospital and Harvard University.
Previous diet studies had pointed to a benefit for vitamin B against breast cancer, the second-leading cause of cancer death in the U.S. after disease in the lung. The latest work also suggests that the nutrients may counteract harmful effects of alcohol, researchers said.
High folate levels halved breast cancer risk for women who have more than one alcoholic drink a day. Drinking more than one glass of beer, wine or hard liquor every day can increase women's breast cancer risk by as much as 20 percent, Zhang said.
U.S. health officials recommend 400 micrograms of folate a day -- about as much as in four glasses of orange juice, Zhang said. Women should also eat folate-rich vegetables such as spinach, broccoli and asparagus to prevent other cancers, heart disease and birth defects in babies, she said.
The study also looked at breast cancer trends among women who had not yet undergone menopause. Those with the highest vitamin B12 levels had a 60 percent lower risk of breast cancer than women with the lowest levels of the vitamin.
``We don't have a good explanation of why there would be a benefit for premenopausal women, and not postmenopausal women,' Zhang said.
The research included a subset of women enrolled in the Nurses' Health Study, which has followed more than 121,000 female registered nurses since 1976. The latest work focused on 712 participants with breast cancer and an equal number who were free of the disease.