SAN FRANCISCO – Dermatologists don’t need to check the serum vitamin D levels of every patient, according to Dr. Shelia Fallon Friedlander.

The test costs $100. Unless someone is in a high-risk group, which includes the elderly, dark-skinned, or obese patients; has fat malabsorption; or has limited sun exposure, there is no need to check vitamin D levels, she said at the Women’s and Pediatric Dermatology Seminar, sponsored by Skin Disease Education Foundation (SDEF).

Individuals who eat a lot of salmon may be among the few that don't need vitamin D supplementation.

"I don’t think every person of color who walks into your office needs to get blood levels" checked, but if they have other risk factors, order the test, she said. Many clinicians now routinely check blood levels in the elderly, she added.

Besides dermatologists, patients are seeking clarity about vitamin D supplementation. Among the questions they most frequently ask their physicians:

• Does everyone need supplementation? It is not an absolute, she said. Alaskans who are eating salmon day and night may not need to be supplemented, but the Institute of Medicine (IOM) suggests that supplementation is reasonable for everyone unless it is clear the person does not need it, said Dr. Friedlander of the University of California, San Diego.

• What kind of supplement is best? Some foods can be great sources for vitamin D, especially salmon, shiitake mushrooms, and milk. Vitamin D₃ (cholecalciferol) supplements are thought to be better than vitamin D₂ at raising blood levels, and have a longer shelf life.

• How much is best? For now, stick with the IOM recommendations of 400 IU/day for ages younger than 1 year, 600 IU/day for ages 1-70 years, and 800 IU/day for older people, except for people in high-risk groups, Dr. Friedlander advised at the seminar.

All breast-fed infants also are considered to have a higher risk for insufficient vitamin D because often the vitamin D status of the mother is unknown. Supplementation with 400 IU/day of vitamin D is recommended and is "not a bad idea for all children," she said.

For people aged 9-70 years who are at high risk, "1,000 IU/day is the number that has been batted around" for supplementation, though the IOM recommendations allow up to 4,000 IU/day, she said.

• Is more vitamin D better? No one knows, and there are suggestions in some studies of a detrimental effect from too much vitamin D. It’s clear, however, that too little vitamin D is a problem and a moderate amount of vitamin D is good for the body. But the data in 30-40 studies on vitamin D’s effects on risks for cancer and other problems aren’t clear enough yet to say whether a lot of vitamin D is helpful or harmful, Dr. Friedlander said.

Studies looking at colorectal cancer are supportive but not confirming of the beneficial effects of high levels of vitamin D, while studies on prostate and breast cancer are "really scary," she said. Many studies suggest a protective effect of high levels of vitamin D, but some show increased risks, including a small study showing a higher risk for kidney stones. "There’s a lot of controversy in the literature," she said.

The IOM based its recommendations on the principles of doing no harm and not relying on imprecise, suboptimal data. Dr. Friedlander reminded listeners of what happened with beta carotene supplementation: It was thought to decrease skin cancer risk until data showed it increased the risk for other cancers.

"Vitamin D has a beneficial effect until you hit a certain number. Nobody knows what the number is. In certain situations, more vitamin D may have a negative effect on your health," she said.

• Does vitamin D support bone health? Good studies make it absolutely clear that it does. Supplement levels above the recommended 600 IU/day for most people would be even better for bone health, "but there’s nothing to show that you need to get a gazillion units a day," she said.

• Does vitamin D reduce the risk for other diseases? The evidence that vitamin D may protect against multiple sclerosis, cardiovascular disease, and cancer is imprecise, inconclusive, inconsistent, and insufficient. This will change as more randomized, controlled trials are conducted, she said. "We may find that everyone needs to be on 1,000 IU/day, but right now the data aren’t there," she said.

• Should we get vitamin D from the sun? "No, no, no," Dr. Friedlander stressed. Dermatologists have advised patients to stay out of the sun for good reason. "This is a pseudocontroversy. Sunlight is a known carcinogen. You can’t make vitamin D in your skin without inducing DNA damage." People can get sufficient vitamin D from incidental sun exposure, a reasonable diet, and supplements.

Dr. Friedlander said she has no relevant financial disclosures.

SDEF and this news organization are owned by Elsevier.

Clinicians, Parents Still Confused About Vitamin D