If you’ve been reading about the health problems supposedly linked to vitamin D deficiency — such as heart disease and cancer — getting your levels tested might seem wise. But here are some common myths and realities about D testing.
Myth: Tests can reveal whether your levels are healthy.
Reality: Some doctors, such as vitamin D expert Michael F. Holick, author of “The Vitamin D Solution,” consider vitamin D deficiency epidemic in the United States. Others dispute that because, they say, there’s widespread disagreement about what optimal and insufficient levels are. (The Institute of Medicine says 20 or more nanograms per milliliter of blood is adequate; several other organizations consider 30 ng/ml optimal.)
Levels of D below 20 ng/ml are known to interfere with bone health, but no firm evidence links other health problems to low vitamin D. Certain studies show a link between low levels and obesity and Type 2 diabetes, but “we don’t know if the condition caused levels to fall or vice versa, or if they’re even related,” says Clifford J. Rosen, an authority on vitamin D and director of clinical and translational research at the Maine Medical Center Research Institute in Scarborough.
Myth: We all need screening.
Reality: Testing makes sense if you have osteoporosis (vitamin D helps absorb bone-friendly calcium) or a disorder, such as kidney disease, that affects your ability to make the active form of vitamin D. You should also be tested if you have intestinal problems such as celiac disease, which can affect absorption, or if you take a drug that can do the same, such as cholestyramine (Prevalite, Questran and generics), phenytoin (Dilantin and generics), prednisone or orlistat (Alli and Xenical).
But the U.S. Preventive Services Task Force, an independent panel of health experts, says there’s not enough evidence that testing healthy adults leads to better health. In 2014 the panel opted not to recommend routine screening.
Myth: Testing tells you whether you need supplements.
Reality: There’s no conclusive evidence that healthy people benefit from supplements or that extra vitamin D solves health woes.
“Depression and fatigue are common reasons for ordering tests,” Rosen says. “There’s no data [that] D supplements have any impact on these.”
Prescription-level supplements may be helpful for those who have osteoporosis or who have a disease or use medicine that interferes with D absorption, says Consumer Reports’ chief medical adviser, Marvin M. Lipman. And “an over-the-counter supplement of 1,000 IU [international units] is reasonable even without testing if you spend most of your time indoors, rarely eat fatty fish or drink milk, or are over 65.”
Myth: Test results are always accurate.
Reality: The task force found that test results can vary 10 to 20 percent, depending on the lab or method of analysis. So some people may be told that they’re deficient when they’re not, and vice versa. Genetics may also play a role. For example, research published in the New England Journal of Medicine in 2013 found that most of the study’s African American participants had low levels of vitamin D. But they actually had plenty of vitamin D; it just didn’t show up in the test results.
How much D do you need? The Institute of Medicine recommends 600 daily IU for adults up to age 70 and 800 IU at 71 and older. Lipman recommends 800 to 1,000 daily IU, and the Endocrine Society suggests 1,500 to 2,000 IU for adults at risk of deficiency. (Most experts agree that more than 4,000 IU daily may be harmful.)
Few foods aside from fatty fish, eggs and fortified milk and orange juice have vitamin D, so getting enough can be challenging. (For example, three ounces of cooked sockeye salmon has 447 IU.) If you’re concerned, Consumer Reports’ experts suggest 10 minutes of sunshine per day, or talk to your doctor about a supplement.
Copyright 2015. Consumers Union of United States Inc.
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