Women may lower their risk of breast cancer by getting more vitamin D. In a German study of premenopausal women with and without the disease, those with cancer were more likely to have blood vitamin D levels below 50 nanomoles per liter. (About 35 percent of young U.S. women have levels this low, another study shows.) More study is needed; it's possible the cancer causes the deficiency, says lead author Sascha Abbas, a scientist at the German Cancer Research Center. But the nutrient has many known anti-cancer effects. Women concerned about low vitamin D should aim for 1,000 IU daily from food and vitamin supplements, advises Henry Lim, professor of dermatology at Henry Ford Hospital in Detroit. He adds they should not seek exposure to the sun or use tanning booths, which can boost vitamin D levels but are also linked with skin cancer and premature aging.