Most of the vitamin D in our diets comes from fortified foods. These include cereals, juices, margarine and dairy products. If you are following a vegan diet, most of these foods are off-limits. In addition, the vitamin D that is used in supplements and fortified foods is typically derived from animal sources. Despite these challenges, you can meet your body's vitamin D needs by eating dairy alternatives, taking vegan-friendly supplements and receiving regular exposure to sunlight.
Your body can produce adequate amounts of vitamin D from the ultraviolet-B rays in sunlight. To meet your weekly needs, your arms and legs should be exposed to sunlight for 5 to 30 minutes, two times per week. UV-B rays are at their strongest during summer months between 10 a.m. and 3 p.m. However, your body cannot produce vitamin D from sunlight between late October and early March if you live at or above 42 degrees north latitude and between November and February if you live at 35 degrees north. As such, most North Americans require dietary and supplemental vitamin D during the fall and winter months.
Your ability to produce vitamin D from sunlight is inconsistent and potentially hindered by factors such as pollution levels, time of day and year, your age, skin pigmentation, sunscreen use and clothing. As such, most of your vitamin D should come from dietary sources. Fortified dairy alternatives are the best dietary sources of vitamin D for vegans. For example, 1 cup of unsweetened soy milk contains 2.9 micrograms of vitamin D, which is approximately 19.3 percent of your daily intake.
Vitamin D supplements and additives come in two forms: ergocalciferol, or vitamin D-2, and cholecalciferol, or vitamin D-3. Vitamin D-2 is vegan-friendly and derived from plant sources. In contrast, vitamin D-3 is not suitable for vegans, as it is typically made from sheep's wool or other animal by-products. Because of this, you should be mindful of the source of vitamin D in fortified foods and supplements. In addition, because excessive vitamin D levels can cause kidney damage, you should consult a doctor or dietitian before using vitamin D supplements.
Plants and vegetables naturally contain little if at all any vitamin D. Although mushrooms are not an exception to this, they contain high levels of ergosterol. This compound is a precursor to ergocalciferol, or vitamin D-2. Exposing mushrooms to UV-B rays dramatically increases their vitamin D levels from less than 1 microgram per 100 grams to 491 micrograms per 100 grams. These UV-irradiated mushrooms are equivalent to vitamin D supplements in their ability to increase your vitamin D levels. However, as most commercial varieties are at this time grown without exposure to UV B, you should not rely on mushrooms as a source of vitamin D.
- The Vegetarian Resource Group: FAQs About Vitamin D
- U.S. Department of Agriculture National Nutrient Database for Standard Reference: Soymilk (All Flavors), Unsweetened, with Added Calcium, Vitamins A and D
- Institute of Medicine: Dietary Reference Intakes (DRIs)
- European Journal of Clinical Nutrition; Bioavailability of Vitamin D2 from UV-B-Irradiated Button Mushrooms in Healthy Adults Deficient in Serum 25-Hydroxyvitamin D: A Randomized Controlled Trial
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