In July 2016, the U.K.’s Scientific Advisory Committee on Nutrition (SACN) released a report on vitamin D. It recommended new standards for vitamin D intake and offered advice to the government on how to achieve these levels. In contrast, Health Canada adopted the Institute of Medicine’s (IOM) recommended intakes six years ago but has offered no advice on how Canadians can meet them.
Vitamin D is an unusual nutrient in that short intervals of sun exposure throughout the year ought to be sufficient to meet needs. However, there is insufficient ultraviolet B radiation for skin synthesis in countries in northern latitudes. Hence, reliance on other sources of vitamin D is necessary in Canada between October and May and also for anyone who gets no summer sun exposure whatsoever. It is important to note that UVB required for vitamin D production comes from midday sunshine in May to October when the UV Index is above 3.
The evidence points to needing daily intake of 600 IU per day for most Canadians. This is the minimum amount to protect against moderate to severe deficiency, defined as rickets (in children) and osteomalacia (in adults). This requirement cannot be achieved by diet alone.
The average Canadian ingests about 200 IU. Those who use supplements manage well, but they represent only 30 per cent of the population. Oily fish is the only natural source of dietary vitamin D that is readily available today. Canada has had mandatory vitamin D fortification of milk and margarine since the 1970s and has recently allowed other foods to have vitamin D added, such as fruit juice, soy milk and breakfast cereal.
Acknowledging that it is difficult to achieve sufficient intake from natural food sources alone, SACN recommended that finding food-based solutions become a research priority. The committee has urged the population in the U.K. to take vitamin D supplements in winter, when UVB exposure is not possible. And because the cost of supplements may place an additional burden on people with low income, the U.K. offers them for free to some pregnant women and families with children under age five.
In Canada, the practices of requiring mandatory vitamin D fortification of staple foods and encouraging older adults to take a supplement have kept most of the population free from severe deficiency. However, since the release of the recommendation of 600 IU for everyone from age one to 70 (and 800 IU for those over 70), Osteoporosis Canada, the Vitamin D Society, Pure North and other groups who view the need for supplementation as a high priority have provided the only dietary advice.
Twelve million Canadians do not meet blood level requirements for vitamin D. Effective strategies for improving the situation are needed, as research indicates there are many benefits from vitamin D beyond good bone health, including reduced risk of cancer, cardiovascular disease, dementia, diabetes mellitus, multiple sclerosis and respiratory infections. Further, a study published in Dermato-Endocrinology reports that inadequate vitamin D levels result in an estimated $12.5 billion annually in direct and indirect costs and contribute to 23,000 premature deaths each year.
Beyond an urgently needed campaign in this country to encourage supplement use, there must also be a doubling of vitamin D fortification in foods and an increase in the number of foods that are fortified, to allow more Canadians to ingest an average level of 400 IU per day. Although the recommended vitamin D intake tripled in 2010, food fortification has not kept up.
Finally, sun-safe scenarios should be developed and promoted (e.g., encouraging a brief time of exposure prior to sunscreen use).
With these strategies in mind, it may be possible for Canadians to improve their vitamin D status and live healthier lives.