I have seen in recent years healthy people have been bombarded by stories in the media and on health websites warning about the dangers of too-low vitamin D levels, and urging high doses of supplements to protect against everything from hypertension to hardening of the arteries to diabetes. Even patients are asking about homeopathic alternatives for Vitamin D or homeopathic vitamin D.
But a new research from Johns Hopkins USA finds that blood levels of the so-called “sunshine vitamin” higher than the top of the range suggested by the Institute of Medicine confer no additional benefit. This research finding, combined with results of a previous study by the same group noting potential harm from higher vitamin D levels in healthy people, has urged investigators to prescribe caution.
“Healthy people have been popping these pills, but they should not continue taking vitamin D supplements unchecked,” says study leader Muhammad Amer, M.D., M.H.S., an assistant professor in the Division of General Internal Medicine at the Johns Hopkins University School of Medicine. “At a certain point, more vitamin D no longer confers any survival benefit, so taking these expensive supplements is at best a waste of money.”
Amer stresses that there are some groups of people — elderly, postmenopausal women, and people with kidney disease — who do benefit from higher blood levels of a vitamin vital to bone health. Such groups may need to take supplements.
In an article published online in the American Journal of Medicine, Amer and Rehan Qayyum, M.D., M.H.S., also of Johns Hopkins, describe their review of data from more than 10,000 participants in the National Health and Nutrition Examination Survey (NHANES) from 2001 to 2004. They matched those data with mortality data from the National Death Index through Dec. 2006.
When they looked at deaths from all causes and cardiovascular disease specifically, those with blood levels of 21 nanograms per milliliter of 25-Hydroxyvitamin D — at the top of the range that the IOM considers “adequate” and at the low end of “normal” — cut their risk of death in half. Above 21 nanograms per milliliters, the data suggest that the protective effect appears to wear off.
The primary source of vitamin D is the sun, and although it is found naturally in very few foods, commercially sold milk is usually fortified with it. Amer says as people spend more and more time indoors and slather their bodies with sunscreen when outdoors, concern is rising that many are vitamin D-deficient. But he says there is no set amount of supplementation that can bring someone up to 21 nanograms per milliliter because the way people process vitamins varies.
People should consult with their doctors, Amer says, before starting vitamin D supplements and should have their blood levels checked. Still, he says, “most healthy people are unlikely to find that supplementation prevents cardiovascular diseases or extends their lives,” and there is no consensus among doctors on what is the right level of vitamin D in the blood for healthy people.
There are a lot of myths out there and not enough data,” he concludes.