Shift in vitamin D guidelines has physicians reassessing tests and advice for patients

Concern about vitamin D deficiency has been escalating in the Baltimore office of internist Bimal Ashar, MD, for the past few years. Patients have become increasingly worried that their health problems could be due to low levels of the nutrient.

Dr. Ashar used to regularly recommend that concerned patients get their vitamin D levels assessed with a blood test. He often ended up suggesting they take a vitamin D supplement to boost their daily intake.

But now he plans to curtail that practice in light of a recent Institute of Medicine report, which found that vitamin D deficiency is overestimated in the U.S. and Canada. The report also found that the benefits of vitamin D, besides bone health, have not been proved.

Physicians are urged to recommend supplements of vitamin D only to those who are truly deficient. Inadequate levels can cause rickets in children, and osteoporosis and muscle weakness in adults, according to the National Institutes of Health.

"I think that suggesting we all temper our enthusiasm [about vitamin D] until we have more data is really smart," said Dr. Ashar, an associate professor of medicine in the Division of General Internal Medicine at the Johns Hopkins University School of Medicine.

Maybe taking vitamin D supplements is beneficial, he said. But "what the report is stressing is that we don't have data to show that at this time."

During the past 10 years, the public's interest in vitamin D has surged as an influx of studies touting the nutrient's health benefits have been published. The research indicated that higher levels of vitamin D could help fight cancer and colds, reduce the risk of developing multiple sclerosis and decrease the severity of asthma symptoms.

The IOM's latest findings, which were released Nov. 30, have left doctors grappling with new information that contradicts much of what has been reported.

"It was very much an education process for all of us, to look at the data in its entirety and critically review it in a very thorough manner," said Steven Clinton, MD, PhD, an oncologist who helped write the new report. He is a professor of medical oncology at The Ohio State University College of Medicine.

Glenville Jones, PhD, who also contributed to the report, said he was "quite amazed by the fact that [the data] isn't nearly as clear-cut as some of the advocates have suggested." Jones is head of the Dept. of Biochemistry and a professor of biochemistry and medicine at Queen's University in Ontario, Canada.

Dietary guidance set

An IOM committee of 14 scientists examined nearly 1,000 studies on the benefits and health outcomes associated with vitamin D and calcium concerning cancer, cardiovascular disease, diabetes, hypertension and metabolic syndrome, among other conditions. Calcium was included in the study because of its close relationship with vitamin D.

The committee found strong evidence that vitamin D and calcium play a role in skeletal health. But it said there was inconclusive -- and, at times, conflicting -- data on whether the nutrients have any other benefits. Despite the findings, the committee said research should continue on the nutrients' possible role in other health outcomes, such as cancer and cardiovascular disease.

"We're not saying we're not interested in other health indicators. We're saying the data is not sufficient at present to conclude that [vitamin D] intakes higher than those [recommended] in the report would be beneficial," said Linda Meyers, PhD, a member of the IOM committee and director of the IOM's Food and Nutrition Board. The board establishes guidelines for good nutrition and studies the safety and adequacy of the U.S. food supply.

The committee determined that most Americans and Canadians up to age 70 need no more than 600 international units of vitamin D per day. Adults 71 and older might need as much as 800 IU a day. The recommendations assume that people are receiving minimal sun exposure.

Some physicians say they recommend their patients take as much as 1,000 to 2,000 IU of vitamin D daily.

For a majority of patients, anything above 4,000 IU a day increases risk for adverse affects, such as damage to the kidneys and heart, according to the report. The level is lower for children.

To put its recommendations in perspective, the IOM said milk in the U.S. tends to be fortified with 400 IU of vitamin D per quart. Some dietary supplements contain as much as 5,000 IU of vitamin D3 per daily dose. Vitamin D3 is a form of the nutrient.

For calcium, the IOM suggests between 700 mg to 1,300 mg per day, depending on an individual's age. Upper intake levels vary from 1,000 mg a day for infants 6 months and younger to 3,000 mg a day for youths 9 to 18. Excessive calcium has been associated with kidney stones.

The report found that a majority of Americans get enough calcium and vitamin D. Calcium deficiency, however, was noted among some adolescent girls and post-menopausal women. The elderly might be at risk of excessive calcium intake, the committee said.

Committee members attributed the overestimation of vitamin D deficiency largely to the popularity of blood tests that assess patients' levels of the nutrient, and to laboratories' inconsistent methods of determining when the levels are too low.

Dr. Clinton said such assessments should not be a routine part of a patient's medical care, because most people receive sufficient amounts of the nutrient through sunlight and food and beverages that naturally contain vitamin D or are fortified with it. Instead, he said physicians should make the decision to measure a patient's vitamin D on an individual basis.

The American Academy of Pediatrics is evaluating the IOM report and considering aligning its vitamin D guidelines for youths with those recommended by the IOM. The academy suggests that all infants, children and adolescents receive a minimum of 400 IU a day. The IOM recommends youths receive 600 IU a day.

In 2008, the American Medical Association House of Delegates adopted policy urging the IOM to re-examine the daily reference intakes of vitamin D due to new scientific findings.

Family physician James P. Richardson, MD, MPH, said he sees the benefit of tempering the public's "vitamin D mania." But he is concerned that the IOM report could lead doctors to overlook deficiency of the nutrient among at-risk patients, such as the elderly, who often spend little time in the sun and might not consume products fortified with vitamin D.

"In the elderly patients I see, there is still a lot of vitamin D deficiency -- even by the [new] IOM definition -- going undetected and untreated," said Dr. Richardson, chief of geriatric medicine at St. Agnes Hospital in Baltimore. "These aren't people worried about whether [vitamin D] prevents multiple sclerosis. These are people who are falling because their muscles are weak."

Increasing vitamin D levels of such patients is believed to reduce their risk of falls. But the report said current data do not prove this to be true.

Dr. Richardson doubts the IOM report will change how he screens patients for vitamin D deficiency. But he thinks the findings are important for primary care physicians to consider.

"They don't have to go crazy testing every person who walks in the door for vitamin D deficiency," he said. "Most people will have an adequate level."