Sellers of vitamin supplements are fond of saying that everybody is deficient in Vitamin D, and this means you. It seems like that would be an easy question to answer: just get a blood test and see whether your levels are low. Turns out it's not that simple.
Picture: Neeta Lind
Vitamin D can come from your diet, or your skin can make it with enough exposure to sunshine. It's crucial to your bone health, since Vitamin D tells your body to absorb calcium from your diet, and people who lack Vitamin D are more likely to have certain health problems. So screening for Vitamin D deficiency sounds like it might be a good idea.
The US Preventive Services Task Force considered the issue last year, and concluded there wasn't enough evidence to say whether testing is helpful. Scientists disagree on what level should be considered "low", and there's no proof that taking supplements of the vitamin will make you healthier. As the New York Times summarised:
There is some debate over whether low levels of the vitamin are a direct cause of disease, or simply an indicator of behaviours that contribute to poor health, like smoking, poor diet and a sedentary lifestyle.
The federal task force issued a draft recommendation [now in its final form here] based on a review of evidence from more than a dozen studies that evaluated the effects of vitamin D treatment in generally healthy adults. The studies used vitamin D3 doses ranging from 400 to 4,800 international units daily, and they lasted anywhere from two months to seven years.
The panel concluded that the current evidence was "insufficient to determine the net balance of benefits and harms of screening and early treatment of vitamin D deficiency" in generally healthy adults. Dr. Owens said the committee found a number of potential problems with screening.
The tests may diagnose people as deficient who really aren't: For example, African-Americans have low levels of the form of Vitamin D that registers on the test, leading to false positives even when they actually have plenty of the form their body can use.
Instead of widespread screening, the task force recommends a more personalised approach: if you think you really do have a vitamin deficiency, talk it over with your doctor, who may recommend a test but will take it in context with other information about your health.
Vitamin D Screening Not Backed by Expert Panel [New York Times]