Vitamin D has proven to be extremely important to human health, and most Canadians are deficient in vitamin D if they are not taking supplementation. In recent years, as we learn more about vitamin D and what defines an optimum blood level, some confusion has been generated as to how much vitamin D a person should take.

Fortunately, in a recent edition of the Canadian Medical Association Journal, a very timely update for vitamin D supplementation in Canada provides guidelines as to how much vitamin D supplementation is appropriate.

First of all, let’s talk about the health benefits of vitamin D. It has been known for decades that vitamin D deficiency has negative consequences on the bones. Severe vitamin D deficiency can cause a form of weak bones called rickets in children, or osteomalacia in adults. Low vitamin D also increases the risk of osteoporosis and fracture. Adequate vitamin D supplementation is an important part of osteoporosis prevention and treatment, as well as maintenance of overall bone health.

In addition, vitamin D deficiency has more recently been discovered to have many other health consequences:

  • Low vitamin D levels are associated with an increased risk of death, particularly deaths from cardiovascular disease. Low vitamin D levels are also associated with an increased risk of death from colon cancer.
  • The lower a person’s vitamin D, the higher the risk of heart disease, heart failure, and peripheral vascular disease.
  • Low vitamin D is associated with an increased risk of autoimmune diseases, including Multiple Sclerosis and Type 1 diabetes.
  • Sufficient vitamin D is important for the function of white blood cells, which fight infection. Studies have shown that the risk of upper respiratory tract infection is higher in people with lower vitamin D levels.
  • Low vitamin D levels are associated with overweight and obesity. Excess fat tissue stores away vitamin D, such that less is available for use in the rest of the body. It is not clear whether vitamin D deficiency itself increases the risk of obesity (though this has been shown to be the case in animal studies).

In Canada, there is a small amount of vitamin D supplementation in food products such as milk (which generally contains 100 international units (IU) per cup). This is not nearly enough to reach the levels that we need to optimize our defenses against the medical conditions listed above. While our bodies do synthesize some vitamin D from the sun, production of vitamin D in the skin falls to near zero for four to five months of the year in Canada, due to our latitude, decrease in sunlight hours, and lack of exposed skin in the cold! Sun is a known carcinogen (cancer causing agent), so it makes sense to protect ourselves from excessive sun exposure, and take a vitamin D supplement instead.

The recent Canadian guidelines, published by Dr Hanley and colleagues on behalf of Osteoporosis Canada, has made the following recommendations for vitamin D supplementation:

1. In healthy adults under age 50, without osteoporosis or conditions affecting vitamin D absorption or action: 400–1000 International Units (IU) daily is recommended.

2. Adults over 50 years: supplementation with at least 800-1,000 IU per day is recommended.

3. Doses up to 2,000 IU per day are safe for most people. (Higher doses should not be taken without the supervision of your doctor, as vitamin D can be toxic in excess.)

If you have other medical problems, or do not fit into the above categories, the correct amount of vitamin D supplementation may vary. Speak to your doctor about how much vitamin D supplementation is right for you!

Dr. Sue Pedersen © 2010

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