How Much Vitamin D Do You Need?

Nov. 30, 2010— -- For years, vitamin D and calcium supplements have been touted as contributors to strong bones and teeth. Research has indicated that vitamin D, specifically, may even help ward off such maladies as heart disease, flu and certain cancers.

Now, a new report from a major health body suggests that most Americans may have been getting the vitamin D and calcium they have needed all along, without supplements.

This morning, the Institute of Medicine, an independent, nonprofit organization connected to the National Academy of Science, released a report containing new dietary recommendations for vitamin D and calcium .

Estimated average requirements for the two nutrients were set in 1997 and have not been updated since.

"In 1997, the recommendations were established as a sort of estimate of what the institute thought was proper levels," said Dr. Clifford Rosen, senior scientist at Maine Medical Center's Research Institute and one of the committee member experts on the IOM report. "But now we have true levels, based on firmer data over the last 15 years.

"So there are finally dietary allowances established for the first time, based on the systematic review of comprehensive evidence that wasn't available on a large scale in 1997," he said.

Click here to find out how much vitamin D and calcium you should be getting.

The IOM assigned a committee of experts to review more than one thousand studies related to vitamin D and calcium. And even though the report noted solidified evidence that calcium and vitamin D are essential ingredients for bone growth and maintenance, the review found a surprising a lack of evidence that supported health benefits in preventing illnesses, such as the flu, cancer and heart disease.

"I was surprised by the paucity of evidence available to support that," said Rosen. "There were clearly some associations, but there were no gold-standard randomized trials to support those conclusions."

Still, Americans could find themselves taking 50 to 100 percent more vitamin D to keep up with the new recommended daily levels.

Study Stats

The review committee found that the majority of Americans and Canadians receive the appropriate amount of vitamin D and calcium, except for girls ages 7 to 18. The report also found that postmenopausal women taking supplements may actually be getting too much calcium, which could increase their risk for kidney stones.

"We were very pleased to find that most Americans will be covered for their bone health by taking 600 units of vitamin D and 1,200 milligrams of calcium per day," said Rosen.

Standing by previous recommendations, the committee says infants and children ought to receive 200 to 1,000 milligrams of calcium per day, and older children and adults should get 1,000 to 13,000 milligrams.

Vitamin D Report Useful to Doctors, Patients

The committee made more significant changes to Vitamin D recommendations. Previous estimated average requirements recommended 400 International Units (IUs) a day for everyone. The new IOM report recommends that infants receive 400 IUs of the vitamin per day, and 600 IUs for children and adults. Committee members said that people aged 71 or older may need a bit more -- about 800 IUs per day.

And once vitamin D intake passes 4,000 IUs per day and calcium intake passes 2,000 milligrams per day, committee experts said the risk for harm increases in the body. Very high levels of vitamin D, (above 10,000 IUs per day) are known to cause kidney and tissue damage.

Many doctors and laboratories have recommended a level of 30 nanograms per milliliter or more for Vitamin D levels in the blood, but the committee found that 20 nanograms per milliliter is a level that still helps people to protect their bones. Higher vitamin D serum levels did not show further improvements.

Vitamin D is important to the body as it aids in the absorption of calcium, which in turn helps to form and maintain healthy bones. A deficiency of the vitamin causes rickets in children and a softening of the bones and osteoporosis in adults.

Dr. Sundeep Khosla, president-elect of the American Society of Bone and Mineral Research, said the report is the most complete summary available to date for recommended daily allowances for vitamin D and calcium.

"In general, this is an excellent report, and provides useful information for doctors and patients," said Khosla. "Physicians were looking for guidance in this area, and this report provides that."

Vitamin D: Doubtful Docs

Despite the exhaustive review, some doctors remained skeptical of the report.

Dr. Harley Haynes, vice chairman of dermatology at Brigham and Women's Hospital and professor of dermatology at Harvard Medical School, said that recommendations should have been adjusted for latitude of residence, lifestyle regarding sun exposure and skin color.

"It seems very unscientific to come out with a one-size-fits-all recommendation for a nation as large as the U.S. with latitudes as variable as Key West, Florida and Caribou, Maine, and with a population as diverse in skin color as that of the US," said Haynes.

And despite committee members saying the vast majority of North Americans are receiving an adequate amount of vitamin D, some doctors beg to differ.

Dr. Kevin Cooper, director of the NIAMS Skin Diseases Research Center at Case Western Reserve University in Cleveland, said that there is a very high prevalence of vitamin D deficiency.

"[The recommendations] do not reflect the high prevalence of vitamin D deficiency in patients who practice sensible sun protection or others who live in the North," said Cooper. "Data for adverse effects at normal ranges of serum vitamin D is highly questionable."

Different Study Perspectives

Doctors have studied the effects of vitamin D on a variety of health conditions, including cholesterol, heart disease, influenza, Crohn's disease and breast cancer, just to name a few.

Despite the extensive analysis, Dr. Michael Holick, professor of medicine, physiology and biophysics at Boston University School of Medicine, said that some important studies were still left out of the review.

"Studies have been published on diabetes and vitamin D that were not included," said Holick. "There was a study just released in Japan that showed that children supplemented with vitamin D had 90 percent less influenza."

Dr. Katherine Crew, assistant professor of medicine and epidemiology at New York Presbyterian- Columbia University Medical Center, has extensive experience in breast cancer research. She is currently the principal investigator on a study that analyzes the effects of a high-dose of vitamin D on breast cancer.

"This just shows that more clinical trials are needed to address the potential health benefits and risks of vitamin D supplementation," said Crew.

While the report examined a thousand of its kind, Katz noted concern about the quality of the studies.

Vitamin D Still Up for Change

Dr. Carl J. Lavie, medical director of cardiac rehabilitation and prevention at the John Ochsner Heart and Vascular Institute in New Orleans, agrees that the current recommendations seem reasonable based on the evidence, but evidence continues to change.

"Certainly, people who have very low levels of vitamin D require supplementation," said Lavie. "Low levels are now generally considered to be less than 30, but recent studies presented at the Cardiology meetings are suggesting that optimal levels may be around 42 to 43 range."

Vitamin D research especially will continue to evolve over the next five years, said Dr. Lee Green, associate chair for information management at the University of Michigan.

"I predict it will become clear that current acceptable levels are indeed too low to be healthy," said Green.

Sources and Tips

Natural sources of vitamin D include fatty fish, eggs, mushrooms exposed to sunlight, cod liver oil and ultraviolet rays from the sun. Many doctors recommend 10 to 15 minutes of sun exposure per day to prevent vitamin D deficiency.

But Katz tried to put the sometimes-hyped subject in perspective.

"We must indeed guard against runaway enthusiasm," said Katz. "Vitamin D is a nutrient, not a magic potion."

How Much Vitamin D Should You Be Getting Daily?

Based on Tuesday's report from the Institute of Medicine here are the reccomended amounts of vitamin D recommended daily (from food or dietary supplements)

-Ages 1-70: 600 international units.

-Ages 71 and older: 800 IUs.

Calcium and vitamin D must be taken together to build and maintain strong bones. Here are the recommended daily levels of calcium:

-Ages 1-3: 700 milligrams.

-Ages 4-8: 1,000 mg.

-Ages 9-18: 1,300 mg.

-Ages 19-70: 1,000 mg - but for women the amount rises to 1,200 mg at age 51.

-Ages 71 and older: 1,200 mg.