A Little Sun Goes a Long Way toward Breast Cancer Prevention
January 10, 2008—Vitamin D is in the news again, and this time the sunshine vitamin is fighting breast cancer. In the largest study of its kind, German researchers reported in Carcinogenesis that vitamin D protects against postmenopausal breast cancer.
A necessary nutrient for bone health, vitamin D is also attracting attention for its role in immune function. Several studies have suggested that vitamin D might help protect against breast, colon, and prostate cancers, possibly by inhibiting the growth of cancer cells and stopping cancer from spreading.
Most previous studies have looked at the effect of vitamin D obtained from foods—such as egg yolks, butter, fish, and fortified foods—on breast cancer risk. But foods aren’t able to satisfy the body’s requirement for the vitamin by themselves. By far, the most abundant source of vitamin D is from the body itself upon exposure of the skin to sunlight. With the widespread use of sunscreens and decreased time spent outdoors, vitamin D deficiency is becoming increasingly common. People living at higher latitudes are at particularly high risk for vitamin D deficiency during the winter and spring months.
The new study compared the blood levels of vitamin D in 1,394 postmenopausal breast cancer patients with those of 1,365 healthy postmenopausal women.
Having a higher vitamin D level was associated with a lower risk of having breast cancer. The relationship was stronger in women who had never used hormone therapy and in women who had been pregnant two or more times. The researchers noted that vitamin D’s protective effect was more pronounced at lower levels; at higher levels, its protective effect leveled off.
While this study wasn’t able to answer the question of how much vitamin D is needed for breast cancer protection, many doctors recommend that women supplement with 1,000 IU per day. It’s also reasonable—and a good idea—to expose the hands, arms, and face to the sun during the middle of the day for about 15 minutes, three times per week during the summer months, and to skip the sunblock altogether during the winter months in northern areas. Cod liver oil can also be a terrific source of vitamin D, supplying up to 400 IU in 1 teaspoon of the oil.
(Carcinogenesis 2007;e-pub ahead of print)
Kimberly Beauchamp, ND, earned her bachelor’s degree from the University of Rhode Island and her Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. She cofounded South County Naturopaths in Wakefield, RI. Dr. Beauchamp practices as a birth doula and lectures on topics including whole-foods nutrition, detoxification, and women’s health.
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