(Xinhua)
Updated: 2007-12-20 11:36

OTTAWA -- Ethnic people other than whites have insufficient levels of vitamin D and are thus at a higher risk of debilitating diseases such as osteoporosis, cancer and diabetes, according to a Canadian study released Wednesday.

Researchers conducted Vitamin D tests on a group of University of Toronto students and found that virtually all non-whites lack vitamin D in their bodies due to their dark skins, the Canadian press reported.

The findings reinforced the importance of skin color, 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, researchers say.

The research, which is awaiting publication in a medical journal, found that 100 percent of those of African origin were short of vitamin D, as were 93 percent of South Asians (those of Indian or Pakistani origin), and 85 percent of East Asians (those of Chinese, Indochinese or Filipino origin, among other countries).

Insufficient vitamin D amounts were also found among those of European ancestry, but were less widespread, at 34 percent of those surveyed.

The research, based on blood tests conducted at Toronto 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 color and diet are among the most important, researchers stress.

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, they say.

Some of the levels 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, the researchers warn.

Insufficiency in the study was defined as a blood level of less than 50 nanomoles/liter, or about half the amount found earlier this year to prevent cancer in a US trial.

Most of a person's vitamin D is made when skin is exposed to strong spring and summer ultraviolet light. 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 Dr. Reinhold Vieth, a professor in the department of nutritional sciences at Toronto University and one of the researchers.