CALGARY, ALBERTA. It is now well established that people with low levels of vitamin D are at increased risk for osteoporosis and bone fractures. Vitamin D can be obtained from an appropriate diet, but is mainly generated through exposure of the skin to sunlight. Several studies have shown that people living at northern latitudes (at or above 42o N) tend to be deficient in vitamin D during the autumn and winter months. Researchers at the University of Calgary have just released the results of a study aimed at determining the extent of vitamin D insufficiency in people living in Calgary (latitude 51o 07' N). The study involved 60 men and 128 women (aged between 27 and 89 years) who had their levels of the vitamin D metabolite 25- hydroxyvitamin D [25(OH)D] measured every three months for a one-year period. Not surprisingly, the researchers found significantly lower levels during autumn and winter than during spring and summer. They also observed that 34 per cent of the participants had 25(OH)D levels below 40 nmol/L at some point during the year (usually during the autumn). A level of 40 nmol/L indicates a pronounced insufficiency and some researchers believe that even levels as high as 80 nmol/L are insufficient. Virtually all participants in the Calgary study (97 per cent) had levels below 80 nmol/L during at least part of the year. A major clinical trial concluded that people with a 25(OH)D level of less than 68 nmol/L had a four times higher risk of bone fractures than did people with higher levels.
Dr. Reinhold Vieth, a world-renowned vitamin D researcher, believes that most Canadians are deficient in
vitamin D and recommends daily supplementation with 1000 IU (25 micrograms) of vitamin D3.