D-fence Against the Canadian Winter: Making Insufficient Vitamin D Levels a Higher Priority for Public Health

Résumé

With most of the country situated above the latitude of the 42nd parallel north, there is a significant portion of the Canadian population that is not getting enough of the sunshine vitamin during the winter. Vitamin D is naturally produced when skin is exposed to sunlight, however during the winter months in Canada the sun is too low in the sky for this to occur. A full quarter of the Canadian population is estimated to have vitamin D levels so low as to be considered insufficient or deficient by Health Canada guidelines. Increasing vitamin D intake should be considered a public health priority. Vitamin D deficiency is known to be linked to rickets in children and osteomalacia in adults (bone softening and malformation) as well as osteoporosis (loss of bone density, increasing susceptibility to fractures). However a growing body of evidence also suggests that vitamin D may have a role in the prevention of chronic diseases such as heart disease, high blood pressure, diabetes, cancer, cognitive decline, Parkinson’s disease, multiple sclerosis and arthritis. There is, of course, no way to change Canada’s proximity to the equator. But there are ways to help Canadians get more vitamin D through dietary intake. Improving the vitamin D status of the Canadian population through food fortification and dietary supplements represents an inexpensive intervention that can improve the health of the population, but debate remains over how much vitamin D the Canadian population needs and how to ensure the population adheres to whatever recommendations are made. Food fortification has already demonstrated its effectiveness in improving vitamin D levels (as it has for other public health priorities, such as with iodized salt). Decades ago, the prevalence of rickets in Canadian children led health professionals to lobby for, and win, legislation making vitamin D fortification mandatory for milk. Other foods, such as orange juice, milk of plant origin and margarine are sometimes also fortified with vitamin D. However many Canadians do not consume milk or the other fortified foods or do not take dietary supplements at the current recommended levels, increasing their risk of vitamin D insufficiency. It is clear there is a need to gain a better understanding of the benefits and the costs of strategies associated with vitamin D intake in the general population. There have been longstanding concerns about the risk of people consuming too much vitamin D (leading to hypercalcemia). More recently there has emerged great disagreement in the scientific and regulatory communities over what constitutes an excessive dosage of vitamin D, and even what constitutes the optimal blood-serum level for vitamin D. The inability to settle on firm guidelines is paralyzing any movement towards increasing vitamin D intake in the Canadian population. Fortification and public health strategies are needed to ensure current vitamin D targets are met. Health Canada’s proposal to allow greater levels of vitamins and minerals to be added to foods, to meet consumer demand (within maximum limits), has been on the table since 2005. A decade later, the Canadian winters have grown no shorter, and the solar zenith angle has not changed. It is becoming an increasingly urgent matter of public health to reach a consensus on updated guidelines for vitamin D intake levels and limits, to better inform Canadians.