Sunlight and Vitamin D: To be or not to be?

Sunlight and Vitamin D: To be or not to be?

TORONTO - It is a generally accepted fact that sunlight is a natural source of vitamin D and that this vitamin is responsible for a variety of health benefits including the prevention of cancer. However, excess of sunlight leads to the development of skin cancer.

It is this catch-22 situation that doctors and researchers from all over North America will attempt to solve as they meet in Toronto this week. This meet is being organized under the aegis of the Canadian Cancer Society.

"There's been mounting scientific evidence to suggest that being in the sun unprotected -- that is, not using sunscreen -- may reduce your risk of some big cancers, like breast, prostate, colorectal and non-Hodgkin's lymphoma," said Heather Logan, a director of cancer control policy at the Society.

"But we know, based on a solid body of evidence, that exposure to ultraviolet radiation can increase your risk of skin cancer, premature aging and cataracts. It's not an easy situation to deal with, and what we don't want people to do is to end up outside unprotected -- to trade cancers for cancers."

Logan added that exposing the hands and feet to sunlight for just about 5 to 10 minutes is known to boost the levels of the vitamin in the body. Edward Giovannucci of the Harvard School of Public Health said that in summer, just 20 seconds of exposure will produce 400 International Units (IU) of the vitamin.

This is the current recommendation followed all over Canada and the United States for almost all age groups. He added that laboratory studies had provided irrefutable proof that vitamin D inhibits rapid multiplication of cells (which leads to cancer), thus averting the condition.

"Cells are becoming relatively starved of the vitamin D ... and they can't really function 100 per cent properly. At least that's the hypothesis, that these lower levels of vitamin D may be increasing the risk of cancers and other conditions," Giovannucci said.

"Probably 1,000 IU is a real minimum and realistically we probably need to go up to 2,000 IUs, which is the upper limit before you worry about toxic or adverse affects." But medical experts differ on the exact time and the nature of exposure that would be ideal. The Canadian Cancer Society said that it was hoping to release some concrete guidelines by the middle of May.