Vitamin D-fense
August 4, 2011
by Maura Harrigan, MD, RD, CSO
Vitamin D is the next hot topic nutrient with promise for new applications in health promotion and disease prevention. Before we look ahead, let's just take a look back. Remember, vitamins were discovered through rigorous research of diseases which were determined to be a result of overt deficiencies. Remember rickets? No? That's because fortifying milk with Vitamin D has virtually wiped out this childhood disease of defective bone growth. Eradication of rickets is the result of the adoption of an effective public health policy based upon good research. Adding any vitamin to correct a diagnosed deficiency is very different from mega-dosing that vitamin. The dose matters. More is not necessarily better. And so far the hoped-for benefits of mega-doses of other vitamins, such as A and E, have not been borne out by research. The science keeps pointing us back to consuming whole foods, not supplements. This is an especially important concept for cancer survivors.
But just how much Vitamin D is needed is currently being debated among scientists. To help clarify this issue, the Institute of Medicine tasked an expert committee with reviewing the evidence and updating the Dietary Reference Intake (DRI) for Vitamin D. An exhaustive review of studies found that the evidence supported a role for Vitamin D in bone health but not in other health conditions. Overall, the committee concludes that the majority of Americans are receiving adequate amounts of Vitamin D. In fact, there is emerging evidence that too much Vitamin D may be harmful. Again, more is not necessarily better.
As tests for Vitamin D levels have become more widely used, confusion among the public has grown about how to interpret results. The measurement for deficiency used by laboratories has not been set based upon rigorous scientific studies and is not standardized by a central authority. The IOM committee stated blood levels of Vitamin D above 20 nanograms per milliter to be the level needed for good bone health.
The 2011 Institute of Medicine DRI for Vitamin D
600 IU age 50 and under
600 IU ages 51-70
800 IU for those over 70
For more information visit www.iom.edu/vitamind
How much is too much Vitamin D?
The current Tolerable Upper Intake Level (UL) number is 4,000 IU.
Vitamin D is a fat soluble vitamin which means any extra not needed by the body remains stored in the body. The potential for toxicity exists, affecting kidney function, weakening muscles and bones. An overdose usually comes from supplements, not food or sunshine.
Here are some ways we can take in adequate amounts if Vitamin D:
Make sure not only kids, but adults too, are drinking plenty of milk (preferably skim) instead of soda, vitamin waters or energy drinks.
Let's all get outside and take in a natural dose of Vitamin D by walking in the sunshine, without sunscreen, for 5 to 30 minutes twice a week.
Vitamin D-rich foods:
Cod liver oil, 1 T 1,360 IU (your grandmother was on to this!)
Salmon, cooked 31/2 oz 360 IU
Mackerel, cooked, 31/2 oz 345 IU
Tuna, canned in oil, 3 oz 200 IU
Sardines, drained 1 3/4oz 250 IU
Milk, all types, 1 cup 98 IU
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