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[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. "

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