January 3, 2011

New Vitamin D Recommendations: Not So Sunny?

By Dr. Laura Sternweis
Iowa State University Extension Scott County

Research shows that vitamin D may play a role in lowering the risk of certain types of cancer, cardiovascular disease, type 2 diabetes, immune and infectious disorders, physical performance and some autoimmune diseases. But how much vitamin D does a person really need for optimal health?

The Institute of Medicine’s (IOM) Food and Nutrition Board believes that vitamin D studies during the past 10 to 15 years present conflicting and mixed results. Although leading vitamin D researchers recommend vitamin D supplement levels of 2,000 international units (IU) or 4,000 IU — or even 10,000 IU in particular situations of demonstrated deficiency — the IOM believes that recommending such high levels is unwarranted. The vitamin D researchers, however, are quick to point out that the majority of the IOM members do not have experience with vitamin D research.

The IOM’s newly released recommended dietary allowance (RDA) for vitamin D suggests 600 IU for people age 70 and under, and 800 IU for those over age 70. This is a slight increase beyond the previous RDA (200 IU for children and younger adults, 500 IU for adults age 50-70 and 600 IU for older adults).

However, the IOM claims that the majority of Americans and Canadians are getting enough vitamin D. Yet, some medical practitioners believe that many individuals are deficient. Research at McGill University Health Centre in Canada suggests that 59 percent of people are deficient in vitamin D and 25 percent are severely deficient.

What is a person to do? The Iowa State University specialists suggest the following steps.

1. Engage in outdoor activity whenever possible and let the sun work its magic. Just 20 minutes of direct sunlight (prior to applying sunscreen) will stimulate adequate vitamin D production in individuals under age 70. At peak summer sunlight (10 a.m. to 2 p.m.), exposure of the face and hands to the sun for 15 to 20 minutes produces 10,000 IU of vitamin D.

2. Consume foods fortified with vitamin D including milk, margarine, cheese and orange juice. Naturally occurring sources of vitamin D include fatty fish, such as tuna, salmon and mackerel, as well as egg yolks and beef liver.

3. Consider a vitamin D supplement if living in northern climates and dietary intake of foods listed above is not consistent. Many experts recommend 1,000 IU/day during the summer and fall with marginal sunlight exposure and 2,000 IU/day during the winter and spring.

For more information, contact Laura Sternweis, Extensions Communications and External Relations at 515-294-0775 or lsternwe@iastate.edu