Occasionally I have disagreements with an MD friend inHawaiiwho 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. He simply runs from his condo across the sand to the ocean each morning and in short order, the sun on his skin converts a form of cholesterol (which our bodies can make) into a precursor of vitamin D, which then travels to the liver and kidney where its conversion to vitamin D is completed.
Whereas when we have limited sunlight from October through March, I can stroll onStanleyPark’s seawall, or along theLangley’s Fort to Fort trail, and even several hours of daylight won’t assist me in creating this vitamin.
Why does this matter? Vitamin D has a tremendous impact on our ability to absorb calcium from our diets, retain it, and reduce losses of calcium through the urine. In these ways, vitamin D aids in forming and maintaining strong bones. In recent years, scientists have recognized that this vitamin may help us to maintain a healthy immune system and prevent certain types of cancer, MS, and depression. (Heading south in winter sure cheers me up!) Due to our northern latitude and limited ultraviolet Bradiation during winter months, many Canadian adults have very low levels of vitamin D by the time April rolls around. Children inCanadahave insufficient stored vitamin D to last through the winter months.
For these reasons, those of us who don’t live in places likeHonolulumust rely on vitamin D fortified foods or supplements during winter. The substances that are used in foods and supplements may come either from oily fish, fish livers, or animal skins and wool (vitamin D3 or cholecalciferol), or from non-animal sources such as yeast that has been exposed to light (vitamin D2 or ergocalciferol). Very few foods contain vitamin D so it has been added to milks (soy, rice and cow’s milk). In choosing soymilk or rice milk, be sure to choose the fortified forms. If you want a vegetarian form of vitamin D as a supplement, a good choice is SISU’s Calcium and Magnesium 2:1 which contains ergocalciferol.
From April on, when the sun is higher in the sky, how much sunlight do we need? If our skin is light, about 15 minutes on our hands, forearms and face will do the trick. (If we head toWreckBeachand strip down, just a few minutes of greater skin surface exposure will suffice.)
It’s important to balance our need for vitamin D with common sense. Sunscreen with an SPF of 8 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 is dark, we need about 30 to 45 minutes of sun exposure on our hands, forearms and face daily. By 70 years of age, our skin’s ability to produce vitamin D is just 30 percent as effective as that of a young adult so 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 dietary or supplementary sources of vitamin D.
For more information on vitamin D, see “Cooking Vegetarian” by Forest and melina,, “Becoming Vegetarian” (US title), “Becoming Vegetarian” (Canadian title), by Melina and Davis; “Becoming Vegan” by Davis and Melina; “Raising Vegetarian Children” by Stepaniak and Melina; and http://ods.od.nih.gov/factsheets/vitamind.asp.
Quick Chocolate Shake
This shake, from “Becoming Vegetarian”, is an excellent source of calcium, vitamins D and B12, and instant energy. To freeze bananas, select those that are ripe as they are much sweeter, with less starchy aftertaste. Peel the bananas, place them whole or in chunks in plastic bags or containers, and freeze. Fresh lemon juice sprinkled on the bananas will keep them from turning brown. Frozen bananas last several weeks, depending on their ripeness and on freezer temperature.
1 banana, fresh or frozen, peeled and broken into chunks
2 teaspoons cocoa powder
3/4 cup fortified soymilk or rice milk
In a blender, place banana, cocoa and fortified milk. Process until smooth.
Makes 1 1/4 cups
Vesanto Melinais a registered dietitian and author of seven classic books on food and nutrition. For personal nutritional consultations, call 604-882-6782 or email email@example.com. Website: www.nutrispeak.com.