NUTRITION
August 1, 2006

Keep on the Sunny Side

Here is a surprise for those of us who are afraid to sunbathe for fear of skin cancer. According to a new study, exposure to UVB radiation from the sun can reduce your risk of 16 different types of cancer. These include gastrointestinal cancers, urogenital cancers, lymphomas, and head and neck cancers.

So sunlight is now good for you? Not exactly. Spending too much time in the sun can still cause skin cancer, but exposure to sunlight carries benefits, as well. One of the most important is that it causes the body to produce more vitamin D; and it is vitamin D, not sunlight itself, that appears to protect against a variety of cancers.

"This study provides important additional support for the vitamin D/cancer hypothesis" according to researcher William Grant. "The mechanisms whereby vitamin D reduces the risk of cancer are well known, and include effects on intercellular adhesion, apoptosis (programmed cellular death), the inhibition of angiogenesis around tumors [starving blood stupply to cancerous tumors], and the inhibition of metastasis [stopping the cancer spread]."

Published in the August 2006 issue of Anticancer Research the study sorted through health data from 49 states and the District of Columbia for two periods: 1950-69 and 1970-94.

Grant's co-author, Dr. Cedric Garland of UC San Diego's Moores Cancer Center, points out that you do not have to sunbathe to increase your vitamin D levels — you can achieve the same level of cancer protection by taking dietary supplements. "While solar ultraviolet B is not always available or convenient for synthesis of vitamin D and entails a possible small increase in risk of nonmelanoma skin cancer, vitamin D supplements are readily available and nontoxic in the preventive range of 1,000-1,500 IU/day."

According to Grant, "Other recent studies recently found that it takes 1000 to 1500 International Units (I.U.) of vitamin D per day to reduce the risk of cancer incidence and death by 30-50%. In the U.S., dietary sources provide only 250 to 300 I.U. per day. People with fair skin living in the sunnier regions of the country can make 1500 I.U. of vitamin D in about 20 minutes near solar noon with 10-20% of their body exposed. Those with darker skin require 2-4 times as much time or body exposed for the same vitamin D production. This may help explain why black Americans have higher cancer incidence and mortality rates than white Americans, which was described recently in the Journal of the National Medical Association."

Garland added, "Briefly exposing a large enough area of skin for adequate vitamin D synthesis is more effective than increasing the amount of time spent in the sun. Protracted exposures to the sun are counterproductive after the 20-30 minutes at most when vitamin D synthesis for the day is complete. People of all ages should wear a hat whenever spending more than a few minutes in the sun, and should spend the time walking or otherwise in motion."
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