By Carey Rossi on December 3, 2010 in
It's official: cold season is upon us. There's a lot of sneezing and wheezing going on in the ConsumerSearch.com offices and it makes this editor wonder if her colleagues should be getting more of the superstar vitamin -- D. For the last four years, the sunshine vitamin has been hogging the nutritional research limelight and as we embark on Cold and Flu Watch 2010/2011, it's continuing to be the scene-stealer. On Tuesday of this week, the U.S. government panel responsible for setting the recommended daily intake levels for vitamins announced that the daily recommended intakes (DRIs) for vitamin D were increased.
Specifically, the Institute of Medicine (IOM) increased the DRIs from 400 IU to 600 IU for persons between the ages of 1 and 70, and to 800 IU for those over 70 years of age. This action is causing quite a stir, as the recommendation is not nearly as far as the vitamin D research community wanted.
Defining D
First of all, it's important to understand the unique nature of vitamin D: You don't consume the working form of D, your body makes it. Your cells convert the two forms of D -- D2 (found in plant sources) and D3 (produced by the body through sun exposure or consumed from animal products or supplementation) -- into its active form, the steroid hormone 1, 25-dihydroxyvitamin D. Sounds like we're vitamin D factories, doesn't it? The truth is we're not.
It has been reported that three-quarters of all Americans are vitamin D deficient. Specifically, a study in the September 2009 issue of the journal, Pediatrics, found that 70 percent of children had insufficient levels of vitamin D. And this is a big deal because being D deficient has been linked to cardiovascular diseases, such as hypertension and heart disease; cancer; fibromyalgia; chronic muscle pain; diabetes; and depression.
Another thing to consider during this germ-festive season: not getting enough D may inhibit your immune system and set you up for more colds. A study published in the May 2010 issue of the American Journal of Clinical Nutrition found that daily supplementation with 1200 IU of vitamin D3 reduced the incidence of seasonal flu (influenza A) by over 40 percent in school-age children. The Japanese scientists from Jikei University School of Medicine concluded that there is "a cause and effect relationship...;between the dietary intake of vitamin D and contribution to the normal function of the immune system and healthy inflammatory response, ..."
Making D
So why aren't we producing as much D as we need? For one, we're protecting ourselves from skin cancer. By wearing sunscreen of an SPF 8 or higher, we inhibit the photosynthesis of ultraviolent B rays that our bodies use to produce 1, 25-dihydroxyvitamin D. Also, if you live in northern climates, sunshine is weak for about half the year. Finally, there are relatively few foods that provide us with vitamin D -- fatty wild fish like mackerel, herring and cod liver oil and porcini mushrooms. Therefore, supplementation can make up the difference. And this is where the confusion begins.
New Daily Recommended Intakes of D
On November 30, the IOM released its report stating the new DRIs for vitamin D and calcium after reviewing 1,000 scientific studies. The end result is that the 400 IU DRI of years past was increased to 600 IU. However, there's a lot of confusion with this number. First, it is difficult to compare it with suggestions of yore -- those were adequate intake recommendations versus the daily recommended intakes that were released this week. The new report states that 400 international units (IU) of vitamin D daily is sufficient for most people (this is the old adequate intake amount), but the recommended intake (known as the DRI) is 600 IU for people from ages 9 to 70 and 800 IU for people over 70.
Either way that you slice it, this isn't in line with the recommends made by researchers who specialize in studying vitamin D. (None of whom sat on the IOM's "Committee to Review Dietary Reference Intakes for Vitamin D and Calcium".) In a paper published in the September 2010 issue of Proceedings of the Society for Experimental Biology and Medicine (now known as Experimental Biology and Medicine), well-known vitamin D researchers Anthony W. Norman, PhD, of the University of California, Riverside, and Roger Bouillon, PhD, at the Universite Leuven in Belgium, call for an increase in the amount of vitamin D recommended to 2,000 IU daily. The authors state this amount would reduce disease frequency as well as cut medical costs. The IOM Committee didn't agree.
So now what?
The one thing that both the IOM committee and Norman and Bouillon agree on is that vitamin D dosing is individual. For instance, someone in sunny California who isn't diligent about sunscreen will most likely need to supplement their diet with less vitamin D than a Portland, Maine, resident -- especially during the winter months.
The best thing to do is have your blood serum vitamin D levels checked at your next physical. (The test is called 25-hydroxyvitamin D or 25(OH)D. Levels should be above 50 ng/ml (125 nmol/L) year-round, in both children and adults.) More physicians are aware of the importance of D on health so this shouldn't be an odd request. Armed with the results from that blood test, your doctor and you can determine the best course of action for getting enough D to keep you healthy.