D is for different

Vitamin D is a unique nutrient because it can be made by our skin when we're exposed to ultraviolet (UVB) rays. That's why vitamin D is called the sunshine vitamin. We can also get vitamin D from foods such as milk, which happens to be our main food source of this vitamin.

D is for discovery

Besides teaming up with calcium to build strong bones and prevent bone diseases such as rickets, vitamin D may have other potential roles in health. A growing body of research suggests that a high level of vitamin D in the blood may help to:

• Increase muscle strength, thereby reducing the risk of falls and fractures in older people
• Prevent premature cell aging and protect against colon, breast and prostate cancers and
• Help prevent diabetes, hypertension and certain autoimmune diseases such as multiple sclerosis and Crohn's disease.

D is for deficient

Despite the importance of vitamin D, tests show us that the blood levels of vitamin D in Canadians aren't high enough to offer protective benefits. Living in the northern hemisphere combined with spending long hours indoor at home or work result in limited exposure to sunlight. During November to March, there aren't enough UVB rays in Canada for the skin to naturally produce vitamin D.

Sunscreens with a SPF 15 or higher also block vitamin D production by up to 98 per cent. To get a good dose of vitamin D from the sun, your face and lower arms generally need to be exposed to the summer sun without sunscreen for five to 15 minutes between 10 a.m. and 3 p.m., three times a week. These are general guidelines only. If you're age 50 or over or if you have darker skin, you will be less efficient at producing vitamin D. In fact, people with darker skin produce vitamin D six times more slowly than people with lighter skin.

D is for dosing

Adults up to age 70 need 600 IU of vitamin D a day. Even if you consume foods rich in vitamin D such as milk, it's almost impossible to get this amount unless you take a supplement. Canada's Food Guide recommends that adults over the age of 50 take a daily supplement of 400 IU as well as follow the advice of Canada's Food Guide for milk and alternatives and other food groups.

D is for delicious

There are many delicious food sources of vitamin D. By law in Canada, milk is fortified with vitamin D, making it an excellent food source for the vitamin. Two cups (500 mL) of milk provide 200 IU of vitamin D. Margarine and certain beverages (such as orange juice) are fortified with vitamin D. Some yogurts and fresh cheeses are made with fortified milk, and thus they also contain vitamin D. Only a few foods naturally contain vitamin D - fatty fish (such as salmon, sardines, herring and trout), egg yolks, and some mushrooms. Cod liver oil also contains a high amount of vitamin D, but it isn't very popular these days!