Vitamin D tests conducted on a group of University of Toronto students have found that virtually all non-whites had insufficient levels of the sunshine vitamin, putting them at elevated risk of debilitating diseases such as osteoporosis, cancer and diabetes.
The research, which is awaiting publication in a medical journal, found that 100 per cent of those of African origin were short of vitamin D, as were 93 per cent of South Asians (those of Indian or Pakistani origin), and 85 per cent of East Asians (those of Chinese, Indochinese or Filipino origin, among other countries).
The findings have alarmed the researchers, who say that if the results are typical of Canada's growing non-white population, the country could be facing a public health crisis.
"I think it's important to take measures as soon as possible for this," said Esteban Parra, an anthropologist at the university who worked on the study and said the result "really surprised" researchers.
Insufficient vitamin D amounts were also found among those of European ancestry, but were less widespread, at 34 per cent of those surveyed.
The research, based on blood tests conducted at the university's Mississauga campus in February and March, is the first to systematically examine vitamin D levels of a group of racially diverse, young Canadian adults and categorize the results by ethnicity.
A variety of factors influence how much of the vitamin people have, but skin colour and diet are among the most important.
The results indicate that Canada may have to revise its vitamin D intake levels and increase awareness about the risk of deficiencies, particularly among non-whites.
Some of the levels found - among people from all ethnic groups - were so low that if the students had been infants, they would have been at risk of the debilitating childhood bone disease known as rickets. Insufficiency in the study was defined as a blood level of less than 50 nanomoles/litre, or about half the amount found earlier this year to prevent cancer in a U.S. trial.
Currently, Health Canada doesn't have a racially based recommendation for vitamin D, and tells everyone to take the same amount. It didn't respond to requests for its reaction to the study, but said earlier this year that it was interested in reviewing the country's vitamin D recommendations.
The Canadian Cancer Society, however, earlier this year advised non-whites that they need to consume more than whites. The recommendation, through diet and supplements: 1,000 IU a day year-round for non-whites, and that amount in fall and winter for whites.
The new study vindicates the cancer society's approach, and also suggests that the country's main food-fortification strategy - adding vitamin D to milk and infant formula - doesn't work for non-whites as they get older, although it helps prevent rickets during infancy.
The idea of adding the nutrient to milk was adopted when the population was mainly of Northern European origin, the group most likely to drink the dairy product over a full lifetime and least likely to have allergies to it.
The U of T findings reinforced the importance of skin colour, which has been known for more than a decade to be a factor determining how easily a person is able to make vitamin D at a given latitude.
Most of a person's vitamin D is made when skin is exposed to strong spring and summer ultraviolet light, hence its nickname the sunshine vitamin. Those with darker skins have more pigmentation due to melanin, a natural sunscreen, that slows the ability of skin to make the vitamin.
"The darker your skin, the lower your average vitamin D level will be. There is no doubt about it," said Reinhold Vieth, a professor in the department of nutritional sciences at the university and another of the researchers. Dr. Vieth said Canada needs a public health strategy that includes more information about vitamin D, particularly for those at risk of deficiencies based on skin colour.
