Although some people don’t get enough vitamin D, and a deficiency of it can cause problems, a federal panel has determined that the jury is out on whether routine testing for vitamin D level in the blood makes sense.
The U.S. Preventive Services Task Force, (USPSTF) an independent body of experts in prevention and evidence-based medicine, makes recommendations to improve the health of all Americans. It has determined, according to a story on NPR, that there are problems with vitamin D testing as a standard practice of preventive medicine. The USPSTF issued an “insufficient evidence” statement meaning that the evidence is unclear on whether benefits of the test outweigh potential harms.
Yes, most people don’t get enough sunshine, especially this time of year, for their bodies to make vitamin D, and, yes, testing is increasingly popular, but as we blogged a couple of years ago in “Vitamin D – Fashion or Fiction?,” even if you do need the vitamin supplement, how much and for how long depend on why you’re deficient, your diet and other medication you take.
As explained by the National Institutes of Health (NIH), vitamin D is found in small amounts in fatty fish (herring, mackerel, sardines and tuna), and is added to dairy products, juices and cereals – that’s what’s meant when you see labels reading “fortified with vitamin D.” But most vitamin D – as much as 90% of what the body gets – is obtained through exposure to sunlight. And it doesn’t take much time in the sun to get sufficient amounts.
As medicine, vitamin D is used to prevent and treat rickets, which disfigures bones. It’s also used to treat weak bones (osteoporosis), bone pain (osteomalacia), bone loss in people with a condition called hyperparathyroidism and the inherited disease osteogenesis imperfect, in which the bones are especially brittle and easily broken. It’s also used to prevent falls and fractures in people at risk for osteoporosis, and to prevent low calcium and bone loss (renal osteodystrophy) in people with kidney failure.
Vitamin D might be prescribed for conditions of the heart and blood vessels, including high blood pressure and high cholesterol, and for diabetes, obesity, muscle weakness, multiple sclerosis, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), asthma, bronchitis, premenstrual syndrome (PMS), tooth and gum disease, some skin conditions and to boost the immune system.
But it’s far from a one-size-fits-all approach to preventive medicine.
Although some studies have shown a relationship between low levels of vitamin D and various disorders (higher risk of bone fractures, falls, heart disease, colorectal cancer, diabetes, depression and thinking problems), the scientists who evaluated studies for the USPSTF concluded that no direct evidence exists for universal screening as a way to reduce those risks.
“The effect of vitamin D levels on health outcomes is difficult to evaluate,” the USPSTF statement says.
According to its report:
- There is no consensus of what defines a vitamin D deficiency. Different professional societies set different minimum levels, from 20 to 30 nanograms per milliliter of blood.
- Test results can be tricky to interpret because testing methods aren’t consistent; there is no internationally recognized standard.
- Adequate levels might vary among ethnicities; African-Americans typically have lower levels, but it’s unknown if the difference signifies a problem.
Tests aren’t cheap – they cost between $50 and $220. And the typical vitamin D dose generally is not dangerous. So because the vitamin itself is not expensive, some doctors believe it’s OK just to tell people to take supplements and not bother with a blood test. It’s vitamin insurance, not vitamin deficiency diagnosis.
Too much vitamin D can be unsafe. Some side effects of overdosing are weakness, fatigue, sleepiness, headache, loss of appetite, dry mouth, metallic taste, nausea, and vomiting.
Taking vitamin D for long periods of time in doses higher than 4000 units per day is possibly unsafe, according to the NIH, and might cause excessively high levels of calcium in the blood.
In 2010, the Institute of Medicine (IOM), another nonprofit research outfit that’s not an agency of government, issued a report acknowledging vitamin D’s vital role in bone health, but also said evidence was lacking that low levels of it cause disease. The IOM recommended that adults as old as 70 get 600 milligrams of vitamin D a day, and those who are older should get 800 milligrams.
Whether you should be tested for vitamin D levels should be a decision by you and your doctor. But if you’re generally well, if you don’t have an elevated risk of osteoporosis, it’s probably not necessary, at least on the current state of the evidence.