Q: I wonder if I'm getting enough vitamin D during the winter months. Is it best to get it from the sun, from fortifi ed foods (like milk), or from supplements? How much vitamin D do I need?
A: Vitamin D is often called the sunshine vitamin. However, vitamin D is not really a vitamin at all, it is a pro-hormone. Th is vital prohormone plays many roles in optimal health including:
Vitamin D is acquired from three sources: good old sunshine, dietary intake, and more and more from supplementation.
We can obtain adequate vitamin D from UV light; however, during the winter months decreased sun exposure leads to decreased serum vitamin D conversion. Not to mention, we have become a sun-phobic society. Daily sun protection is a delicate balance and we may have tipped the scales. Decreased UV exposure in the winter and increased use of sunblock in the summer may be a reason many Americans are vitamin D defi cient.
Vitamin D defi ciency, exhibited as rickets, was fi rst identifi ed in the 17th century as a disease of the wealthy. Th e members of aristocracy did not go outside much. Furthermore, over the centuries it was noted that Northern European populations had a higher incidence of rickets than southern populations. Cod liver oil was identifi ed as a common cure for rickets, but the cause was yet to be discovered. Fortunately, in the 1920’s vitamin D was identifi ed and subsequently fortifi ed in the food supply.
Vitamin D is a fat-soluble vitamin that we store in the liver. Due to our ability to store D, adequate sun exposure in the summer months can carry us though the winter months.
Vitamin D is unique because we can absorb it from UV light but there are also dietary sources of this essential nutrient. If you don’t get much sun exposure in the summer, then you may need to supplement. You can go “Food First” to get your daily dose of D with vitamin D-rich foods (see below).
Supplements are also available in the vegetarian form of D2, or D3 derived from fi sh oil or lanolin. Th e recommend Daily Allowance for vitamin D is 600-800 IU for adults, and 400 IU for children. Th e National Institutes of Health Offi ce of Dietary Supplements list the Upper limit for vitamin D supplementation to be 4,000 IU for adults. It is conservative to take 2,000 IU daily if you believe you are at risk for a vitamin D defi ciency. Ask your health care provider to test for serum D levels.
Joey Miller has a passion for good food, health, and nutrition which led her to become a registered dietitian after receiving a B.S. & MPH Nutrition Science from UC Davis. She has worked in the natural foods industry for over 13 years, including 6 years at the Sacramento Natural Foods Co-op. Joey specializes in longterm care with experience in infant and child nutrition.