Vitamin D and Thee
Lately, there's been a flurry activity surrounding vitamin D. We probably need much more than the current Dietary Reference Intake (DRI) advises. That standard, set in 1997, is the amount needed to prevent rickets, but new research justifies reevaluating the current recommendation. But even at those low levels, most Americans do not meet the recommendations. Are YOU getting enough vitamin D? What should you do about it?
What does vitamin D do?
Vitamin D helps the body to absorb calcium and to maintain the correct balance of calcium and phosphorus in the blood. In doing so, it protects the bones from becoming thin and brittle. It also helps with nerve and muscle function, immunity and reduction of inflammation. Vitamin D may inhibit some certain cancers and have a role in preventing autoimmune diseases like multiple sclerosis.
D in the diet
National surveys (NHANES) show that only 29 percent of men and 17 percent of women eat enough vitamin D. That’s because it is in very few foods. Important sources are oily fish like salmon, mackerel, herring, tuna, and cod liver oil. Good sources are egg yolks, liver, and mushrooms that have been exposed to ultraviolet light.
Fortified foods provide most of the vitamin D in the diet. Milk has been fortified with vitamin D since the 1930s but other dairy products, such as cheese and ice cream, are generally not fortified. Ready-to-eat breakfast cereals are often fortified, as are some brands of orange juice, yogurt, and margarine.
Food manufacturers are not required to list vitamin D content on the food label unless a food is fortified, but generic foods emanating from the USDA National Nutrient Database contain vitamin D information. For example, see the vitamin D in this generic egg yolk. See more extended nutritional details.
"The Sunshine Vitamin"
Vitamin D is produced in the skin from the ultraviolet (UVB) radiation of sunlight. The UVB radiation converts stored vitamin D to its active form. Daily requirements can be met with 15 minutes of sunshine on a bare arm, but most of us aren’t exposed to enough sunlight due to sunscreens and working indoors. Synthesis is also limited due to cloud cover, smog, dark skin color, and the the winter season; however, vitamin D is stored during the summer for off-season use.
Are you D-ficient?
The 25-hydroxyvitamin D blood test is the best way to measure vitamin D levels in the body, but the test is not standardized and so the results may vary from lab to lab. Although the minimum and maximum values are clear, the best levels for good health remain blurry. And the standards for sub-sets of the population - men, women of various ages, and non-Caucasians - are even more elusive. The Institute of Medicine has empaneled a committee to evaluate the criteria for determining deficient, marginal or insufficient, and adequate levels of vitamin D. They will report their findings in Fall 2010.
Take D supplement?
Presently, the government recommends 200 to 600 IU of vitamin D a day but for optimal health, much more seems to be needed. Vitamin D scholar, Dr. Michael Holick, recommends taking up to 2,000 IU a day. The DRI for vitamin D will be updated soon and the requirements are expected to increase.
Meanwhile, it is essential to meet the current recommendations for vitamin D by drinking fortified milks, eating oily fish and spending time in the sunshine. It is also prudent to take a supplement that contains active vitamin D (cholecalciferol) to achieve, at very least, the current recommendation.
Are you concerned about vitamin D?
The side effects of allergy medications keep some people from using them. Natural remedies can be a great alternative, but some are more effective than others.