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Sunlight, Vitamin D and the Health of Canadians

By John-David Kato, DC, MSc, ACSM-RCEP, CSEP-CEP. Posted May 24th, 2008.

The weather is finally warming up after a cold, snowy winter. This means that many people will be covering up or slathering on the sunscreen and heading out into the sunlight. Over the last several decades there has been much public education on the dangers of getting sun burnt and the risks of skin cancer, however experts are becoming concerned that Canadians may not be getting enough sun. Sun exposure is the best way to get Vitamin D but it is estimated that about 97% of Canadians have inadequate levels of Vitamin D at some point during the winter and spring months. Some people are deficient even in the summer. The following weblog is about the importance, production and sources of vitamin D, as well as reasons why so many Canadians have inadequate levels.

Why is Vitamin D so important?
Vitamin D plays a very important role in the absorption and use of calcium for bones but it helps control the function of many other tissues in the body, which has gained a lot of attention from researchers in recent years. Many people are aware if its role in bone health for preventing rickets in children and osteomalacia in adults, however there is lots of research now to suggest that it plays a role preventing many other diseases as well. For example, Vitamin D has been shown to reduce the chance of developing cancers such as colon, prostate, pancreatic, breast and ovarian cancer. It has been shown to reduce the risk of respiratory infections like the common cold, the flu and tuberculosis. It seems to play a role in reducing the risk of autoimmune conditions where the immune system attacks the person's own organs. Such conditions include multiple sclerosis, rheumatoid arthritis and type 1 diabetes. Vitamin D has been shown to help in reducing symptoms of PMS, reduce the risk of cardiovascular disease, type 2 diabetes, low back pain and chronic musculoskeletal pain.

How is Vitamin D made?
Vitamin D is actually more like a steroid hormone than a vitamin because vitamins are generally not made in the body. It is produced mainly in the skin where it is transformed by ultraviolet light (specifically ultraviolet B rays) from the sun. It is because of this sunlight requirement that has been given the name the sunshine vitamin. And for many people, 15 minutes of sun exposure in a bathing suit is enough to get a healthy dose of vitamin D. Once absorbed into the blood stream it is further transformed by the liver, and then the kidneys. It is this final form, often called vitamin D3 or calcitriol , that it is the active form in the body and has the various health effects. And regardless of how much sun you get, research suggests that the body is able to regulate how much vitamin D it makes.

If the body can make it, why do so many Canadians become deficient?
There are many factors. As I alluded to before, because of the controversy and legitimate concern of skin cancer, many people stay covered up, or continuously use strong sunscreen. These barriers block the ultraviolet light and prevent the conversion of vitamin D by sunlight. Furthermore, because Canada is at a higher latitude on the earth the combination of the angle of the sun's rays and the shorter daylight hours means we get less ultraviolet light in the winter and spring months. I suspect that washing your skin immediately before and right after sun exposure would remove the available vitamin D that would otherwise be absorbed into the body. People with darker skin are also at higher risk because their skin pigments block the ultraviolet light. They can therefore require up to 5 times the amount of sun exposure. Other factors that affect Vitamin D levels include smog, older age, obesity, certain medications and medical conditions.

Are there are some dietary means to get Vitamin D?
Yes, sunlight is the best source, but there are sources of Vitamin D that we can get nutritionally. Vitamin D is present in oily fish and fish oils. Similar to sunlight and vitamin D, there is also a controversy of mercury levels that is present in these kinds of fish but the benefits to your health by having fish once or twice a week probably outweighs the risk of mercury. (For more information about fish and mercury, I suggest checking out ) Other sources of vitamin D include foods that are fortified with it such as milk, rice milk, soymilk, some cereals and orange juice. For people who are vegan, one important source is sun dried shiitake mushrooms. And finally there are supplements that have vitamin D. The Canadian Cancer Society recommends a supplement dose of 1000 IU/day (see link below). Some people may need more but that depends on how much sun you get, your health status and how deficient you are, however you should consult a qualified health practitioner in this case.

In conclusion, protecting yourself from sunburn is still important, but research has shown that not getting enough vitamin D has greater risks of chronic pain, cancers, infections, heart disease and inflammatory diseases. Vitamin D can come from different dietary sources, but for many people about a few minutes a day of direct sun exposure will give you a good dose that can go a long way to help prevent many of these chronic conditions.


  1. Canadian Cancer Society, Vitamin D,,3182,3172_1176359459__langId-en,00.html
    accessed May 24th 2008.

Disclaimer: The information is provided for general knowledge only. As each person has different individual needs there is no guarantee the information specifically applies to the person reading it. If you require professional advice or care please contact Dr. Kato.

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