NUTRISPEAK

by Vesanto Melina MS, RD

Occasionally, I have disagreements with an MD friend in Hawaii who insists that vitamin D is not a vitamin, meaning that it is not essential in our diet. What does he know? For him, it isn't essential. Simply running from his condo to the ocean each morning, in short order, the sun on his skin converts a form of cholesterol, which our bodies can make, into a precursor of vitamin D. It then travels to the liver and kidneys, where its conversion to vitamin D is complete.
Here in BC, from October through March we have limited sunlight, and even several hours of daylight won't help my body to create this vitamin. This is important because vitamin D has a tremendous impact on our capacity to absorb and retain calcium. It also reduces the loss of calcium through our urine. In these ways, vitamin D helps us form and maintain strong bones. In recent years, scientists have recognized that vitamin D may help the immune system to stay healthy, and that it plays a role in preventing certain types of cancer, MS and depression. (A winter holiday in a sunny southern spot sure cheers me!) Due to our northern latitude and limited ultraviolet B radiation during winter months, many Canadian adults have very low levels of vitamin D, and, by the time April rolls around, children have an insufficient amount of stored vitamin D.
Those of us who don't live in places like Honolulu must rely on vitamin D-fortified foods or supplements during winter, deriving from oily fish or their livers (remember cod liver oil), or from animal skins and wool (vitamin D-3 or cholecalciferol), or from non-animal sources, such as yeast that has been exposed to light (vitamin D-2 or ergocalciferol). As very few foods contain vitamin D, it is added to soymilk, rice milk and cow's milk. Be sure to choose the fortified forms of soy or rice milk.
From April on, when the sun is higher in the sky, how much sunlight do we need? If we have fair skin, about 15 minutes on our hands, forearms and face will do the trick. If we head to Wreck Beach and strip down, just a few minutes of exposure will suffice. It's important to balance our need for vitamin D with common sense. Sunscreen with an SPF of eight or more inhibits skin vitamin D synthesis, so after a bit of sun exposure, we can slather it on. On cloudy days, the energy of ultraviolet rays is cut in half.
Skin pigmentation and age also affect our vitamin D production. If our skin pigmentation is dark, our hands, forearms and face need about 30 to 45 minutes of daily exposure to the sun's rays. By 70 years of age, our skin's ability to produce vitamin D is only 30 percent as effective as that of a young adult. We are likely to need a supplement or fortified beverage in addition to a little sun exposure. It is important for individuals who are confined indoors to include good sources of vitamin D in their diets.

Vesanto Melina is a registered dietitian and author of seven classic books about food and nutrition. To book a personal nutrition consultation, call 604-882-6782 or email vesanto@nutrispeak.com. www.nutrispeak.comwww.nutrispeak.com





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