Mom always told us we needed to spend time in the sun, but watching sunscreen commercials makes us wonder if we should venture beyond the front door unless the moon is shining. Do we really need sunshine? And if so, do we dare step outside for 10 minutes without sunscreen?

According to the National Cancer Institute, up to 50% of those living in the US are at high risk for vitamin D deficiency. Vitamin D deficiency has been linked with several cancers as well as conditions such as osteoporosis and cardiovascular disease. Over the past year, studies have been published demonstrating a significant reduction in the incidence of breast cancer, lung cancer, and colorectal cancer in those receiving the equivalent of 1000 IU’s of vitamin D daily. For those who have been diagnosed with cancer, increased survival geographically going from north to south has been correlated with sun exposure, and hence vitamin D.

So how do we get vitamin D? Historically, sun exposure has been the main source of vitamin D. While our approach has traditionally been to recommend dietary sources of vitamins alone, this is difficult with vitamin D. Even with vitamin D fortified foods, to get 1000 IU’s per day would require drinking 10 glasses of milk! The Canadian Cancer Society has advised that individuals should consider taking a supplement of 1000 IU’s of vitamin D daily during the fall and winter months. In the US, the American Society states that some people may require supplements, and this should be discussed with your health care provider.

What do the authors do? Spending 10 to 15 minutes in the sun without sunscreen (sunscreen with an SPF > 8 blocks formation of vitamin D) in average summer attire, can result in the absorption of a whopping 5000 IU’s. Of course, this is not recommended for everyone, sun protection (hats, sunscreen) should be used after this time, and you should never burn.

But what if it is cloudy? Many things affect how much vitamin D is produced in our bodies by sunlight, including latitude, complexion, season, and time of day. Clouds reduce absorption by 50% and shade by 60%. People with fair complexions require much less sun exposure to absorb vitamin D than those with darker complexions. At latitudes above 40N (northern California), very little vitamin D is produced during the winter months, and hence the Canadian Cancer Society’s recommendation for a supplement.

Have a Sunny Day!

For information on cancer prevention, visit Avoiding Cancer One Day At A Time.
Copyright 2008 Turtle Lake Publications

Posted by Lynne Eldridge, MD

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