TORONTO (CP) - Sunlight may be the easiest and most natural way to get a health-enhancing dose of vitamin D, but Canadians should know that a little sun goes a long way, says a Canada-U.S. consensus group formed to determine the risks and benefits of exposure to ultraviolet rays.
In what has turned out to be a delicate balancing act, the group is advising that while too much time in the sun raises the risk of skin cancer, avoiding it entirely can lead to a deficiency in vitamin D - and that may elevate the risk of other types of cancers and diseases.
Many Canadians and Americans from northern states are deficient in vitamin D, a nutrient produced by the body through the skin's exposure to sunlight. The consensus group acknowledges that a decade of public health messages to limit exposure to the sun may be responsible in part for that widespread deficiency.
"This is an issue of weighing risks and benefits," said Heather Logan, director of cancer control policy for the Canadian Cancer Society, one of the organizations involved in the consensus group, which released its findings and recommendations Thursday.
"So while sunlight is important for a person's health, we know that you don't need to get a tan in order to get the benefits," Logan said. "Just a little bit of sun goes a long way."
The advisory group, a coalition of health-related associations from Canada and the United States, has reiterated the long-standing caution that too much UV radiation from the sun or tanning lights is potentially dangerous: it can cause skin cancer (including the deadliest form, malignant melanoma) and cataracts.
Experts agree that sun protection is needed when the UV index is three or higher, usually between 11 a.m. and 4 p.m. during warm-weather months.
But at the same time, adequate levels of vitamin D can promote health by helping to build strong bones in children and maintaining them into old age, as well as possibly preventing certain malignancies, in particular colorectal cancer.
Vitamin D deficiency has also been linked to multiple sclerosis, a disease that tends to occur more frequently among populations in northern or extreme southern climes.
"It might be possible for some people to get enough sun to produce adequate vitamin D levels through a five-minute walk, perhaps early in the morning," said Logan. "Five minutes a day is an example, but it's going to vary depending" on the individual.
"Unfortunately, we need more research to be able to be more crisp in telling people exactly how long to be out in the sun . . . There's no simple answer."
How much sun someone can safely tolerate to produce enough vitamin D depends on their age, where they live and their complexion. Darker-skinned people take longer to absorb UV rays compared with lighter-skinned individuals because they have higher melanin levels. While that may mean dark-skinned Canadians can safely stay out in the summer sun a bit longer, the downside is that they have more difficulty making vitamin D during winter months when sunshine is low.
Because few foods contain vitamin D - it is found naturally in such oily fish as salmon, tuna and sardines and is added to milk, soy beverages and margarine - the Dietitians of Canada is recommending for the first time that Canadians take supplements.
"The amount that we think people need now is a lot more than you could possibly get from diet unless you ate fish every day, and not just fish but the right kind of fish," said Susan Whiting of the Dietitians of Canada, one of the organizations that helped formulate the recommendations.
"In order to compensate for not getting as much sun exposure, we need more dietary (sources) and it has to be supplements," Whiting, a professor of nutrition at the University of Saskatchewan, said from Saskatoon.
Current recommended daily allowances for vitamin D - which experts say are woefully outdated and inadequate - advise that children and adults over age 70 need 400 international units (IUs) a day, while adults up to age 50 require only half that amount.
Whiting said 1,000 IUs of vitamin D is a far more realistic amount for all ages, up to a maximum of 2,000 IUs daily, depending on the individual.
Reinhold Vieth, director of the Bone and Mineral Laboratory at Mount Sinai Hospital in Toronto, said the recommendations break new ground because they endorse supplementation of a vitamin for the first time.
"Supplementation means 'Take more vitamin pills.' To me that's new," said Vieth, an internationally recognized expert on vitamin D.
He's also pleased to see a subtle shift in the message about sun safety, which he called an evolution in thinking.
"What they're recognizing in regards to the UV message is that it does not apply to everybody. They've accepted the fact that some Canadians don't have white skin, and that they're at particular risk for vitamin D deficiency."