Vitamin D: The Sunshine Vitamin
Vitamin D is known as the sunshine vitamin because your body makes vitamin D when your skin is exposed to the sun. Vitamin D is needed for your body to absorb calcium, so it is often linked to healthy bones. Only a few foods contain vitamin D naturally—mushrooms are one example of a vegan food that provides some vitamin D. Some mushrooms that have recently become available are exposed to ultraviolet light, which increases their vitamin D content. The main dietary source of vitamin D for many Americans is the vitamin D added to cow's milk. Vegan sources of vitamin D are also fortified foods; vitamin D is added to some brands of plant milks, fruit juices, and breakfast cereals.
Vitamin D needs do not increase in pregnancy. The RDA for vitamin D in pregnancy is 600 IU, the same as for nonpregnant women.
Vitamin D Production
It doesn't take much sun exposure to make all the vitamin D that you need. If you're fair skinned and can be out in the summer sun, experts estimate that you need about five to ten minutes a few times a week on your arms and face to meet your needs. This is a very rough estimate, however, and many factors can affect the production of vitamin D.
Sunscreen and clothing block vitamin D production, so if you'd like to get vitamin D from the sun, wait a few minutes before putting on sunscreen or covering up. Remember though, that use of sunscreen is important to lower your risk for skin cancer.
Can I get too much vitamin D from the sun?
Your body only produces the vitamin D that it needs, so even with a large dose of sunlight you won't make excessive amounts of vitamin D. Of course, too much sun has potential to increase your risk of skin cancer, so don't overdo it!
If your skin is darker or if you live where there's a lot of air pollution or it's a cloudy day, you will need more sun exposure to make vitamin D. Winter sun in the northern part of the United States is not strong enough to promote vitamin D production. If you live in the north in the winter, don't get out in the sun that much, or use sunscreen or protective clothing whenever you're outside, you'll need to know about other ways to meet your vitamin D needs.