Ask a Dietitian

Vitamin D and New Recommended Intake Levels

On June 8th, 2007, the Canadian Cancer Society put forth a new recommendation for vitamin D intake for Canadians. The recommendation was based in part on a new landmark research study that was published in the American Journal of Clinical Nutrition 2007;85:1586-91 (Lappe, JM et al. Vitamin D and Calcium supplementation reduces cancer risk: results of a randomized trial). The study found a significant impact on reducing all-cancer risk in the vitamin D supplemented group. This study adds to the growing body of evidence on vitamin D and cancer prevention but it does have some limitations such as the length of the study being only 4 years and the relatively small subject number of 1200 postmenopausal women.

The Canadian Cancer Society recommendation is for all adult Canadians, in consultation with their doctor, to consider taking a Vitamin D supplement of 1000IU/day in the fall and winter months of October to April. For people at higher risk of having lower vitamin D levels such as those who are older, with darker skin, who don’t go outside or who wear clothing that covers most of their skin, they should take a supplement all year round.

This recommendation is similar to the one released earlier this year by the Canadian Dermatology Association of 1000IU for all adults to reduce the risk associated with skin cancer. The current DRI for adults is 200IU/day and for adults over 50 is 400IU/day. It is known that dietary sources of Vitamin D such as milk, fatty fish, fortified margarine, orange juice and soymilk, sun-dried shiitake mushrooms and some yogurts will not provide sufficient vitamin D in the Canadian diet (based on mean intakes as reported in Moore et al., 2005) and therefore supplements are recommended, in particular for those without sun exposure.

The UVB rays in the sun activate vitamin D in the skin and between 4-8 minutes in the sun in the spring and summer months, arms and legs exposed may provide the 1000IU needed for light skinned individuals. East Asian would need 15 minutes and Africans would need closer to 18 minutes in the sun without sunscreen. Because of the risk of skin cancer this is not the best option.

More research is required to know exactly what amount of vitamin D is needed for bone health and cancer prevention but it is known that the current DRI is too low.

The current upper tolerable limit (UL) for vitamin D is 2000IUand this is thought to be too low as well. New recommendations for pregnancy are for 2000IU/day.

The Bottom Line: Consider a combination of strategies to obtain adequate Vitamin D through minimal sun exposure, foods sources of vitamin D, fortified foods and supplements.