HOW MUCH IS TOO MUCH VITAMIN D?

Once again vitamin D has come back into the limelight as a star nutritional performer. In the early twentieth century, it was hailed as the cure for rickets and osteoporosis, etc. But then researchers found that too much could be toxic; now recent investigation has revealed that it is not only essential, but that it can actually increase longevity. There is still controversy in the scientific community about the optimum daily intake, but there is no question that vitamin D is indispensable for healthy bones as well as other health issues. As we were taught in high school health classes and read in the media, it promotes the absorption of calcium and phosphorus from the small intestine, a fundamental step for bone growth and repair.

Our own bodies will manufacture vitamin D if we expose our bare skin (no sun screen) to strong sunlight for about 20 minutes a day, but the catch here is that a large proportion of the population, for various reasons, is not doing that. So the simple solution is to take a pill, right? Well, yes and no:

*Yes—for people who live at about or above the 40-degree north latitude mark (about the latitude of New York), supplementation is important because we cannot make enough sunlight in the wintertime. There also are some ailments that impair the small intestine’s absorption of vitamin D, such as Crohn’s disease, celiac disease and cystic fibrosis. In addition, as people age, their skin, intestines and kidneys are less efficient at making vitamin D.

*No—But because this vitamin is available through food sources, such as fatty fish and egg yolks, some cereals, milk and is included in the multivitamins we take, it’s easy to ingest too much if we become overzealous. Vitamin D is fat soluble, which means it is assimilated and stored in the presence of fat and that’s why too much can cause liver toxicity. Signs of vitamin D toxicity are:
    -nausea
    -poor appetite
    -constipation
    -weakness
    -weight loss
    -excessive calcium in the blood, which leads to heart arrhythmia

You are unlikely to get too much vitamin D, but what is a safe level? Experts have come forth with a measurement called The Tolerable Upper Intake Level (UL), the highest intake from all sources that is clearly safe: 2,000 International Units (IU). When I say all sources I mean adding up the units you normally ingest through foods, multivitamins, calcium supplements and medications such as Fosamax with vitamin D and others. The total will most likely vary from day to day, but the point is to have an idea of how much you’re getting over time and try to stay under 2,000 IU per day.

IMPORTANT! Cod liver oil is not a safe source of vitamin D because it also contains retinol. Too much retinol increases the risk of hip fracture.

On the plus side, recent research as found a link between high blood levels of vitamin D and a reduced risk for several kinds of cancers, including breast, colon and ovarian. In addition to those findings, according to an analysis by researchers in France and Italy of previously published studies in the September 10, 2007, issue of the Archives of Internal Medicine, the results of 18 randomized trials spanning 5.7 years and involving 57,311 subjects taking an average daily dose of 528 IU found that individuals taking vitamin D had a 7 percent reduced risk of death from all causes, compared with those who did not.

I’m going to make sure I start getting my daily dose and I hope you do to!

For more information, go to www.health.harvard.edu.

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Disclaimer: The purpose of this weblog is not to dispense medical advice nor in any way is meant to be construed as diagnostic or prescriptive. Always check with your physician before beginning any new program or trying any of the items discussed in the posts that appear on this site.