Vitamin D: How much do we need? Where does it come from?
Vitamin D has been in the news a lot lately. There are many articles about it in medical journals as well, and most of those articles confirm numerous health benefits from it. This critical element is needed by virtually every tissue of the body, so it’s not surprising that there is a large number of health problems caused by a deficiency. This is particularly concerning because almost half of all Americans are low on vitamin D. Those with darker skin color are at especially high risk because it takes more sun exposure to make vitamin D.
80% to 90% of the body’s vitamin D comes from sun exposure. Sun exposure needs to be when the sun is high in the sky, and shouldn’t be enough to cause a sun burn. About 40% of skin needs to be exposed. Sun passing through glass and light from tanning beds don’t stimulate vitamin D production. Use of sun block lotions and clothing that covers most of the skin makes it harder to get enough exposure to the needed ultra violet B (UBV) rays.
For adequate production, people need 6 to 8 minutes a day of sun exposure in summer, and 24 to 97 minutes in winter; the time of day and latitude are significant variables. A light-skinned individual in a swimsuit lying in the midday sun for 30 minutes will create about 50,000 IU of vitamin D in the following 24 hours, but someone tanned or naturally dark-skinned will only produce 20,000 to 30,000 IU after the same exposure. Someone very dark-skinned would produce a mere 8,000 to 10,000 IU in such a situation since melanin decreases UVB effects.
The remaining amount of the vitamin has to come from food but there are only a few foods high in it. The best sources are oily fish like salmon and mackerel, and the yolks of eggs. Fortified cereal and milk as well as red meat are other sources of vitamin D.
Supplements can help, but sun exposure and foods are ideal sources. Fortified cereal and milk as well as red meat are other sources of vitamin D.
Since vitamin D is a fat-soluble vitamin, it is difficult for the body to get rid of excess vitamin D. The recommended intake for adults up to age 71 is 600 IU/day, and for those 71 and older its 800 IU/day. The upper limit is 4,000 IU/day. See your health care provider regarding the dose of vitamin D supplement that is right for you. When people are severely deficient, it is not uncommon for a large weekly dose to be prescribed.
Editorial, “Vitamin D: Way more important in Critical Care than we may have Realized.” In Critical Care Nurse, June, 2017, Vol. 37, #3.
Joel Kreisberg, DC, “Preparing Patients for Proper Sun Exposure.” Integrative Medicine, Vol. 8, #4, August/September 2009
Fiona Hermann, “Vitamin D supplementation, sun exposure for Pregnant and breast-feeding women and their infants.” Midwifery News, September, 2011.