Findings published in the American Journal of Clinical Nutrition indicate that 25 percent of the 5,306 participants of the Canadian Health Measures Survey had blood levels below the RDA of 50 nanomoles per liter.
Supplement users had higher blood levels of the sunshine vitamin, according to the new data, but reliance on food sources may be inadequate to ensure optimal blood levels of vitamin D, according to researchers from the University of Saskatchewan, Statistics Canada, and the Public Health Agency of Canada.
“This suggests that current food choices alone are insufficient to maintain [vitamin D] concentrations of 50 nmol/L in many Canadians, especially in winter,” they wrote in the AJCN.
Currently, only milk and margarine have mandatory fortification with vitamin D in Canada, indicating a potential to expand fortification.
Recently, renowned vitamin D researcher, Michael Holick PhD, MD, Professor of Medicine at Boston University Medical Center, told NutraIngredients-USA.com that the most realistic approach to boosting the nation’s intake of vitamin D is for food manufacturers to increase the dose of vitamin D per serving.
A bleak outlook
The new study adds to findings from a review published last year in the Molecular Nutrition & Food Research, which indicated that inadequate levels of vitamin D may be causing about 37,000 premature deaths in Canada and costing the country billions of dollars.
Scientists from the Sunlight, Nutrition, and Health Research Center (SUNARC) in San Francisco reported that the economic burden was also decrease if vitamin D levels were improved, and would save about $14.4 billion.
On a positive note, the results of the Canadian Health Measures Survey showed that only 5 percent of the people surveyed were vitamin D deficient, defined as blood levels of 25-hydroxyvitamin D (25(OH)D) – the storage form of the vitamin in the body – less than 30 nmol/L.
Led by Susan Whiting, the researchers took blood samples from 5,306 people aged between six and 79. Supplement use was quantified by interviewing the participants.
Results showed that 75 percent of the participants achieved the RDA, with only 5 percent of participants classed as being vitamin D deficient.
“Supplement users had significantly higher 25(OH)D concentrations than did nonusers, and no seasonal differences were found,” wrote the researchers.
“In non-supplement users, the prevalence of 25(OH)D concentrations <50 nmol/L in winter was 37.2 percent overall and was 60.7 percent in non-whites,” they added.
The researchers said that future studies should investigate what determines supplement use and how this differs between ethnic groups.
The lowdown on D
Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 diabetes.
The science supporting the muscle function of vitamin D, as well as the vitamin’s role in immune health, is sufficiently robust to have merited a positive opinion from the European Food Safety Authority’s (EFSA) Panel on Dietetic Products, Nutrition and Allergies (NDA). Despite such proclamations of support, many people across the world are not getting enough vitamin D.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.111.013268
“The vitamin D status of Canadians relative to the 2011 Dietary Reference Intakes: an examination in children and adults with and without supplement use”
Authors: S.J. Whiting, K.A. Langlois, H. Vatanparast, L.S. Greene-Finestone