Vitamin D is essential for the absorption of calcium and is formed in the presence of direct or indirect sunlight. Most people’s bodies are able to store vitamin D during the summer for winter use. On average, about 10 to 15 minutes a day of strong sun on the face and hands for light-skinned people should suffice. Darker-skinned people need 20 minutes and the elderly need 30 minutes sun exposure. Sunscreen lotion rated SPF 8 or above prevents vitamin D synthesis.
Vitamin D is a concern for both vegetarians and meat-eaters as the only non-fortified dietary sources are fatty fish, eggs (if chickens have been fed vitamin D), and mushrooms (if treated with UV rays). But dairy products, margarine, some orange juices, some cereals, and many non-dairy milks are fortified with vitamin D.
People getting insufficient sun or not eating a lot of fortified foods should consider taking a 600 IU (or higher) vitamin D supplement per day. Getting higher doses of vitamin D from sunshine or supplements may protect against cancer and many other diseases but the so far the research is inconsulsive.
What is the difference between vitamin D2 and D3?
Vitamin D2 is aways vegan, while D3 is usually derived from sheep’s wool or fish oil.
While, vitamin D2 and D3 are both effective at raising vitamin D levels, D3 is considered slightly more effective and is more widely available.
Note: If you are trying to raise your vitamin D levels with D2, make sure the laboratory you go to for blood analysis can detect vitamin D2, and not just vitamin D3.
Calcium and Vitamin D for Vegans: Summarized! – Jack Norris RD
See the vitamin D section from the American Dietetic Association’s 2009 Vegetarian Position Paper