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Triple That Vitamin D Intake, Panel Prescribes - WSJ.comClipped from: http://online.wsj.com/article/SB10001424052748704584804575645023841631864.html |
Triple That Vitamin D Intake, Panel Prescribes
By MELINDA BECK
A long-awaited report from the Institute of Medicine to be released Tuesday triples the recommended amount of vitamin D most Americans should take every day to 600 international units from 200 IUs set in 1997.
That's far lower than many doctors and major medical groups have been advocating—and it could dampen some of the enthusiasm that's been building for the sunshine vitamin in recent years.
Many doctors have added blood tests of vitamin D levels to annual physicals, and sales of vitamin D supplements have soared to $425 million last year from $40 million in 2001, according to the Nutrition Business Journal.
The IOM panel also issued new recommendations for daily calcium intake, up to 1,200 milligrams for women 51 and older.
Who Needs Extra D
Some people are at high risk for vitamin D deficiency, and experts believe they may benefit from more vitamin D than the new recommendations:
- People age 50 and older: This group is at increased risk for Vitamin D insufficiency. As people age, their skin is less efficient in synthesizing the vitamin and the kidney is less able to convert it to its active hormone form.
- People with osteoporosis: Vitamin D is crucial for building and maintaining strong bones.
- People with limited sun exposure: This population includes the homebound, those living in northern latitudes and individuals who wear long robes and head coverings.
- People with dark skin: Greater amounts of the pigment melanin result in darker skin and reduce the skin's ability to produce vitamin D from sunlight. People who have immigrated from sunnier climates may find their levels dropping sharply in latitudes where the sun's rays aren't as strong much of the year.
- People with fat malabsorption: Vitamin D requires some dietary fat in the gut for absorption. Individuals who have a reduced ability to absorb dietary fat might require supplements. Fat malabsorption is associated with conditions including pancreatic enzyme deficiency, Crohn's disease, cystic fibrosis, celiac disease, surgical removal of part of the stomach or intestines and some forms of liver disease.
- People taking certain medications:Prednisone and anti-seizure drugs can cause vitamin D to be absorbed and metabolized more quickly, reducing available blood levels.
- People who are obese: Individuals with a body mass index equal to or greater than 30 typically have a low concentration of the vitamin in the blood.
Source: National Institutes of Health Office of Dietary Supplements
It's long been known that vitamin D is essential to maintaining strong bones. But hundreds of new studies have also linked low vitamin D levels to a higher risk of a slew of chronic health problems—heart disease, stroke, diabetes, prostate, breast and colon cancers, auto-immune diseases, infections, depression and cognitive decline. Studies have also suggested that many Americans are vitamin D deficient due to working and playing indoors and slathering on sunscreen.
The Institute of Medicine, an arm of the National Academy of Sciences that sets governmental nutrient levels, said there wasn't enough evidence to prove that low vitamin D causes such chronic diseases; it based its new recommendations on the levels needed to maintain strong bones alone.
"The evidence for bone health is compelling, consistent and gives strong evidence of cause and effect," said Patsy Brannon, a professor of nutritional sciences at Cornell University and member of the IOM panel. For the other health problems, she said, "there are relatively few randomized controlled trials, and even in the observational studies, the effects are inconsistent."
The new recommendations, which cover the U.S. and Canada, call for 600 IUs daily for infants through adults age 70 and 800 IUs after age 71. The IOM assumed that most people are getting minimal sun exposure, given rising concern over skin cancer and latitudes where the sun is too weak to create vitamin D on the skin much of the year. The panel also raised the acceptable upper limit of daily intake to 4,000 IUs for adults, from 2,000 previously.
Those levels do take into account vitamin D from food sources—but only a few, such as salmon and mackerel, contain much naturally. Milk fortified with vitamin D contains about 40 IUs per cup. Most Americans and Canadians need to get much of their vitamin D from supplements.
The IOM panel also issued new recommendations for daily calcium intake— ranging from 700 milligrams for children aged 1 to 3 up to 1,200 milligrams for women 51 and older. The main change from the 1997 recommendations was to lower the recommended level for men 50 to 70 to 1,000 from 1,200. The panel noted that teenage girls may not get enough calcium, and that postmenopausal women may get too much, running the risk of kidney stones.
The changes will impact the percentages of recommended daily allowances of vitamin D and calcium listed on food packages, as well as the composition of school-lunch menus and other federal nutrition programs
The panel dismissed concerns that many Americans and Canadians are vitamin D deficient, noting that there is no scientifically validated level that's considered optimum. Even so, the panel concluded that for 97% of the population, a blood level of 20 nanograms of vitamin D per milliliter is sufficient.
Some vitamin D advocates took particular issue with that assumption. Several major medical groups, including the Endocrine Society and the International Osteoporsis Foundation, have concluded that a level of 30 ng/ml is necessary for optimal bone health.
"Randomized clinical trials have shown that in men and women 60 and older, you see fewer falls and fractures at the 30 ng/ml level," said Bess Dawson-Hughes, endocrinologist and director of the Bone Metabolism Laboratory at Tufts University. She also noted that while healthy people may reach that level taking 800 IUs per day, those who don't go outside, who use sunscreen religiously, have very dark skin or are taking some medications will need more.
Studies have also shown that at levels below 30 ng/ml, the body seeks calcium for everyday needs by leaching it from bones.
Dr. Brannon said the panel found such a wide range of blood levels considered optimal in various studies that it could not settle on a single threshold level. "I think the confusion is understandable. The committee is very concerned about the lack of evidence-based consensus guidelines for interpreting blood levels for vitamin D," said Dr. Brannon. "We strongly recommend that these be developed."
The panel was also concerned about what she called "emerging evidence of concern" about possible ill effects of too much vitamin D. Besides a risk of kidney and heart damage noted with vitamin D levels of 10,000 IUs per day, Dr. Brannon said the panel had seen higher death rates from pancreatic cancer, prostate cancer and other causes in men whose blood levels were above 50 ng/ml. The link is still tentative and may never be proven, she noted: "The difficulty is, you can't design a trial to look at adverse effects."
Other vitamin D advocates had guarded praise for the recommendations. "At least they recognized that there was a need to raise the daily intake level. That's a very important message," said Michael Holick, a professor of medicine at Boston University School of Medicine who testified before the committee in April.
He said that despite the paucity of randomized-controlled trials, the long list of chronic diseases associated with vitamin D does make sense, given that it is actually a hormone that affects virtually every organ in the human body and regulates as many as 2,000 genes.
For his part, Dr. Holick recommends that adults take 2,000 to 3,000 IUs per day—and notes that he had done studies giving subjects 50,000 IUs twice a month for six years and seen no harmful effects. "There is no downside to increasing your vitamin D intake, and there are more studies coming out almost on a weekly basis," he said.
One in particular may help settle whether vitamin D has long-term benefits beyond bone health: The National Institutes of Health has begun recruiting 20,000 men and women over age 60 for a nationwide clinical trial to study whether taking 2,000 IUs of vitamin D, or omega-3 fatty acids from fish oil, is any better than a placebo at lowering the risk of heart disease, cancer than other diseases.
In the meantime, some doctors say the IOM recommendations will not change their belief in testing patients' vitamin D levels and supplementing them as needed.
"I supplement patients who are deficient and they feel better. They come in and say, 'I've been much less achy and stiff or my mood's been better since I've been taking the vitamin D,' said Alan Pocinki, an internist in Washington D.C. Most of his patients are office workers, and 75% of them are below the 30 ng/ml level he considers necessary.
"Do we have the data to prove this conclusively? No. We don't have evidence for much of what we do in medicine, but if you wait for the evidence, you may be depriving your patients of beneficial treatments," Dr. Pocinki said.
Write to Melinda Beck at HealthJournal@wsj.com
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