Vitamin D, known for preventing bone deformities in children and osteoporosis in adults, may also play a significant role in cancer prevention. Recent studies have found lower rates of breast, colon, prostate and ovarian cancer with higher blood levels of vitamin D. The question is: What is the optimal amount?
The National Institutes of Health s Institute of Medicine is considering increasing vitamin D recommendations, which currently top out at 2,000 international units for anyone older than 12 months old. But after reviewing data from 29 studies, researchers concluded a universal intake of vitamin D of at least 2,000 IU and up to 3,500 IU daily in North America could reduce colon and breast cancer rates by 50 percent. Researchers believe vitamin D may help prevent cancer by aiding the immune system in discouraging unnatural cell reproduction, and hindering the formation of new blood vessels for tumors.
Called the ‘‘sunshine vitamin, it is uniquely made by the body with 10-15 minutes of sun exposure twice a week. UV rays transform the inactive form of vitamin D under the skin into the active, beneficial form found in blood, but sunscreen with an SPF of 8 or greater blocks its formation. Rates of cancer are higher in North America possibly because of less sun exposure and weaker UV rays in the winter.
In Boston, for example, sunlight exposure from November to February is insufficient to produce vitamin D. Another way to get vitamin D is through diet and supplementation, though not many foods are a significant source. Fatty fish, like tuna, salmon or mackerel, will provide 200-360 IU per 3-ounce serving.
Fortified milk is the other major dietary source with 100 IU per cup. Lesser amounts are found in fortified cereals and some dairy products. Vitamin D insufficiency is reported to occur in 40 percent of the population.
To meet recommendations, most adults should consider taking a simple multivitamin containing at least 400 IU of vitamin D daily and eat good food sources. Children should be encouraged to drink milk instead of juice and soda. Some doctors are now testing blood for vitamin D levels and recommending additional supplementation when needed.
High-risk populations - dark-skinned people, the elderly, and those with a family history of colon cancer or breast cancer - should discuss the need for additional supplementation with their doctor.
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