Many don’t get enough vitamin D
Most people think that they get all the vitamin D their body needs if they have moderate skin exposure to sunlight. This common belief may be wrong for some people and is clearly not always true even in Hawaii.
Researchers from the University of Wisconsin, in collaboration with Honolulu nutrition researcher Dr. Rachel Novotny, measured the vitamin D blood levels of 93 young adults living on Oahu. Although all participants had "abundant sun exposure," half of them had low vitamin D status. Other researchers have been claiming that there is an epidemic of vitamin D deficiency in the United States. But, finding that many active "sun lovers" in Hawaii had low vitamin D levels was very unexpected.
Question: Why be concerned about vitamin D deficiency?
Answer: More and more chronic health problems are being linked to low vitamin D status. It is widely known that bone health suffers when vitamin D is low. This increases the risk of osteoporosis. Less widely appreciated is the potential importance of vitamin D in the prevention of diabetes, various cancers (breast, colon, ovarian, pancreatic, etc.), and autoimmune diseases such as multiple sclerosis and rheumatoid arthritis.
Some studies are finding that improving vitamin D status in older people helps their muscle strength and decreases falling. Immune function is benefitted by adequate vitamin D. Some researchers even propose that vitamin D may help to battle viral infections, possibly even the common cold and the flu.
Q: How much daily vitamin D is recommended?
A: Vitamin D experts say that the Institute of Medicine recommendations set in 1997 are much too low. When a dietary supplement indicates 100 percent of the "Daily Value" for vitamin D, it contains 400 IU. Current research indicates that people with little sun exposure need four or five times this amount to maintain optimal blood levels of the vitamin.
Q: What are good sources of vitamin D?
A: It is not easy to get enough vitamin D from foods. The major sources are fortified milk (100 IU per cup) and fish that typically provide between 50 and 500 IU per 3-ounce serving. Dietary supplements are available as vitamin D-2 and vitamin D-3. Vitamin D-3 is the most potent form.
Q: Can you get too much vitamin D?
A: The body has protective mechanisms to prevent too much vitamin D production from sun exposure. However, too much vitamin D from foods and supplements can become toxic. The current upper intake level is set at 2,000 IU/day. A consensus of expert vitamin D researchers suggests that this be increased up to 10,000 IU/day.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S. are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dr. Dobbs also works with University Health Services.