Routine vitamin D testing not justified, panel says

More and more people are getting tested for vitamin D deficiency, but the value of the tests remains too murky to make them part of routine medical care, an influential advisory group says.

There simply isn't enough evidence that testing the blood of healthy, symptom-free people for vitamin D deficiency will end up improving people's health, says the draft recommendation released Monday by the U.S. Preventive Services Task Force. The task force — an independent panel whose recommendations influence which prevention measures are widely adopted — also says there's little evidence testing would hurt.

It's true that low vitamin D levels have been linked with problems including bone fractures, falls, cancer, diabetes, heart disease, depression and even early death, the task force says. But studies have not shown that giving vitamin D supplements to apparently healthy people with low levels can prevent those problems.

Another issue: Expert groups disagree on how low is too low when it comes to blood levels of vitamin D. Also, different lab tests can produce different results. Because of varying standards and study methods, estimates of vitamin D deficiency in the U.S. population range from 19% to 77%, the task force says.

"There's a lot of controversy here," says task force co-chair Albert Siu, a geriatrics professor at the Icahn School of Medicine at Mount Sinai in New York.

Indeed, one vitamin D researcher says he's "chilled" by the task force's decision not to endorse widespread screening: "There is no rational or scientific basis to oppose screening of the U.S. population for vitamin D insufficiency when the consequences are so serious," says Cedric Garland, a professor of family and preventive medicine at the University of California-San Diego.

But another proponent of vitamin D supplementation says the task force is right not to endorse widespread screening. "It wouldn't accomplish anything," says Michael Holick, a professor of medicine, physiology and biophysics at Boston University School of Medicine.

Holick takes the view that about two-thirds of adults get too little vitamin D. So he recommends everyone take 1,500 to 2,000 international units (IUs) daily without bothering to get tested. Most people, he says, get too little through common foods (such as fortified milk and salmon) and don't spend enough time in the sun to for their bodies to produce adequate amounts.

A major U.S. study in which people will take the large doses Holick recommends is under way.

But for now, the standard-setting Institute of Medicine recommends lower daily amounts: 600 IU in adults ages 18 to 70 and 800 IU in adults older than 70. It says most people can get that through food.

The task force report says the risk of taking vitamin D supplements to raise blood levels well beyond sufficient levels is "small to none." It says raising levels through sun exposure could increase the risk of skin cancer.

Many people already are getting tested. One study found diagnoses of vitamin D deficiency — presumably through blood testing — tripled between 2008 and 2010.

It's not clear if doctors or patients are driving the demand, Siu says. He says testing can sometimes be appropriate: "It's not a test you should go ask for, but I think it's a reasonable test if a physician believes it would be appropriate for any number of reasons."

One influential group of physicians, The Endocrine Society, recommends vitamin D tests for people at high risk of deficiency, including those who are obese, pregnant or dark-skinned and those who have conditions including osteoporosis and chronic kidney disease.