Guest guest Posted October 15, 2006 Report Share Posted October 15, 2006 [Nice to see this article prominently displayed on the front page of an internal section of the Saturday Globe & Mail] D-FORCE Get your sunshine vitamins Saturday October 14, 2006 MARTIN MITTELSTAEDT ENVIRONMENT REPORTER Now that your winter coat is out of the closet, it's time to focus on the other things you need this season: vitamin pills, salmon and a glass of milk. Chilly weather is definitely here, but right now Torontonians are also facing what some researchers have dubbed a new season, one that profoundly affects everyone in the city -- vitamin D winter. That's the dark time of the year that begins when the sun is so low in the sky that its rays aren't strong enough for the human body to produce the vitamin naturally. Without replenishment from diet or pills, the levels of this " sunshine vitamin " start to crater in all people who live in northern climes during the winter, leaving them susceptible to a host of health problems. Researchers now suspect that the list includes heart disease, diabetes and more than a dozen types of cancers. In Toronto, the vitamin D winter is far longer than its better-known counterpart that brings freezing temperatures and blizzards. A rule of thumb some researchers use is that it begins when the sun is so low in the sky that your shadow, even at high noon, is always longer than you are. This period falls roughly from mid-October to early March. " Starting from now, if you are in Toronto, you can forget it. You will not make any vitamin D even if you go and stand outside without any clothes, " says Rohan Gunasingham, a St. Louis, Mo., physician and expert on vitamin D deficiencies. Until now, vitamin D has been something of the Rodney Dangerfield of the nutrition world, getting little respect for its role in maintaining good health. But a growing number of medical researchers are worried that a lack of vitamin D could pose a health threat. And because the vitamin D winter is so long, almost everyone runs chronically low on this essential nutrient for much of the year. " We have a 4½-month to five-month vitamin D winter. That means that your vitamin D might, if you didn't have any further input, fall by 75 per cent, " says Reinhold Vieth, a nutritional sciences professor at the University of Toronto. Doctors who are concerned about the vitamin say its role is underappreciated by most of their colleagues, but Vitamin D deficiencies are now being linked to a raft of ailments. The best documented are childhood rickets and osteoporosis and fractures in the elderly, but current research is linking low levels to more than a dozen cancers, heart disease, diabetes, the flu and even depression and schizophrenia. The link with cancer is particularly interesting because some types, such as breast cancer, follow a north-south trend around the world, with higher incidences at latitudes where sunlight is sparse for part of the year. Colon and prostate cancer have also been tied to low vitamin D. Measuring the vitamin D winter is something of an inexact science. Some vitamin D researchers say the winter officially starts when the highest angle the sun makes with the horizon during a day falls below 40 degrees. By this measure, the first full day of this winter started in Toronto last week, and it will last until March 5. Another approach is to use Environment Canada's UV index. Vitamin D is made through the interaction of ultraviolet B rays in sunlight and a cholesterol in the skin. An index level of 3 and above indicates vitamin D production. " Once it's less than three, forget it, " according to Dr. Vieth. The UV levels drop in winter because light has to travel through more of the atmosphere before it hits the ground, leading to a filtering effect that cuts down the ultraviolet part of the spectrum. Vitali Fioletov, a research scientist at Environment Canada, says the UV index in a typical year will fall below three in Toronto on Oct. 26. Research by Dr. Vieth suggests most Canadians fall below healthy levels of the vitamin in the winter. The average level among employees at Toronto's Mount Sinai Hospital, where Dr. Vieth also works, was just barely above the level associated with osteoporosis during January and February, according to surveys he has conducted. One of the peculiar aspects of the vitamin D shortfall is that the effect is most pronounced in those with darker skin tones -- who have more melanin, a natural sunscreen that filters out ultraviolet light. This is an adaptation for living in tropical areas where UV radiation is intense year-round, and it becomes a problem in places such as Canada, where UV radiation is more feeble. Dr. Vieth thinks that as a public-health measure, immigrants to Canada from southerly latitudes need to be told that they are at more risk of vitamin D deficiencies than their light-skinned neighbours of European ancestry. This also applies to fair-skinned women from Muslim countries who wear veils in Canada and consequently have almost no sun exposure year-round. " If they move from Lebanon or from Saudi Arabia to Thorncliffe Park in Toronto and continue wearing the same clothing, you can be very certain that their [vitamin D] levels are remarkably low, " he said. During the summer, when sunlight is intense, most light-skinned people in southern Canada can make large amounts of the vitamin with a modest 15 to 20 minutes of daily sun exposure. For the rest of the year, maintaining adequate levels means getting it through diet -- major sources include milk, salmon, sardines and other cold-water fish -- or vitamin pills. There is a big debate in the scientific community on how much supplemental vitamin D is needed in winter. The current minimum daily recommended amount in Canada for those under 50 is 200 International Units, or the amount in one glass of vitamin D-fortified milk. This is tiny compared with the levels of about 10,000 I.U. that the body might produce on a summer day. Susan Whiting, a nutrition professor at University of Saskatchewan, says there is mounting evidence that getting 500 to 1,000 I.U. in winter through supplements is appropriate, and Dr. Vieth thinks even higher amounts are in order. He says we should try to maintain the high levels humans would have where our species evolved, near the equator, where sunlight showers exposed skin with lots of ultraviolet light. " Basically, we're the naked ape, " he said. " They didn't take all that fur off of us for nothing. " Quote Link to comment Share on other sites More sharing options...
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