DECIDING whether to avoid direct sunshine just became more complicated. Keeping out of the sun helps avoid skin cancer, but sunshine also allows your skin to manufacture vitamin D, which plays a key role in preventing colorectal cancer.
In a review of studies examining links between vitamin D and colorectal cancer, Cedric Garland and his colleagues at the University of California, San Diego, conclude that taking 1000 units, or 25 micrograms, of the vitamin daily – equivalent to five times US guidelines for young adults – halves the risk of colorectal cancer.
Vitamin D is thought to prevent colorectal cancer by helping the lining cells of the gut stick together properly, preventing the formation of pre-cancerous polyps.
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“A few minutes’ exposure to the sun produces thousands of units of vitamin D”
“What’s clear is that 1000 units is the minimum to produce an effect,” says Garland. The team estimates that if all US adults consumed 1000 units of vitamin D per day, it could save 28,000 lives each year (Journal of Steroid Biochemistry and Molecular Biology, vol 97, p 179).
Although vitamin supplements are the safest option, the study will reopen the debate about avoiding the sun – not least because about 60,000 Americans die each year from colorectal cancer, versus 2000 from non-melanoma skin cancer. A few minutes’ exposure to summer sun can produce many thousands of units of the vitamin.
