Anybody who’s followed American vitamin fads over the past few decades won’t be surprised by the new vitamin D intake recommendations issued today by the Institute of Medicine.
Although the Institute’s panel of experts tripled the recommended intake of vitamin D for most Americans (from 200 to 600 international units daily), they also stressed that the vast majority of people already get enough of this vitamin through the usual channels (diet and brief exposure to sunlight) to maintain good bone health. Few people need to take supplements, they said.
The panel’s report also makes clear that promoting strong bones is the only proven health claim that can be made for vitamin D. Other claims — that it prevents cancer, heart disease and diabetes, for example, or that it increases immunity — may be interesting areas of research, but have yet to be supported with good solid science.
The 14-member panel, which examined more than 1,000 published studies and took testimony from scientists and others, also expressed concern that ingesting high doses of supplemental vitamin D over a long period may be harmful. Some research (as yet unproven) has suggested that excess vitamin D may increase the risk of pancreatic and esophageal cancer or cause too much calcium to build up in arteries.
This pattern — enthusiastic claims being made for a drug or supplement before truly good research supports it — is one we’ve seen several times before with vitamins. Not so long ago, for example, vitamin E was touted as a cardiovascular protector — until good studies found that high doses of it actually increased the risk of heart disease.
The Institute of Medicine panel set the upper intake levels for vitamin D at 2,500 IUs per day for children aged 1 through 3 years, 3,000 IUs daily for children aged 4 through 9 years, and 4,000 IUs for everybody else. But, as the panel stressed, these upper levels should not be construed as the top of the range that individuals should consume. They just represent a safety boundary.
Vitamin D enthusiasts aren’t taking these new recommendations well, however, judging by some of the angry comments that have been posted in reaction to articles in the New York Times and elsewhere today.
Recommendations for vitamin C
The panel also revisited recommendations regarding calcium, which works side-by-side with vitamin D to build bones. These guidelines mostly stayed the same: 700 milligrams daily for children aged 1 through 3 years, 1,000 milligrams for children aged 4 through 8 years, and no more than 1,300 milligrams daily for adolescents aged 9 through 18 years. For adults, the recommendations are 1,000 milligrams daily for women through age 50 and for men through age 70. Women over the age of 50 and men over the age of 70 should take no more than 1,200 milligrams daily.
The panel also said that, as with vitamin D, most individuals can meet their daily calcium requirements through dietary means alone. Supplements are not usually needed.
Excess levels of calcium, the panel noted, pose their own health dangers — most notably, an increased risk of developing kidney stones.
Vitamin D blood tests aren’t reliable
Anybody who’s had his or her vitamin D blood levels checked in recent years will want to read the panel’s conclusions about those tests. They point out that the criteria that laboratories use to determine such test results are not based on rigorous scientific studies. Nor are they standardized. So you could take the test twice on the same day and be told that you are either deficient or sufficient in vitamin D, depending on which lab processes the test.
According to the panel, a blood level of 20 to 30 nanograms of vitamin D per milliliter of blood (the measurement used in the United States) is all that’s needed for good bone health. Many laboratories currently claim that any reading under 30 nanograms signifies a deficiency. But, as the New York Times reported today, that would mean 80 percent of Americans have a vitamin D deficiency. It would also mean that all of us would need to take vitamin supplements, as we wouldn’t be able to reach 30 nanograms through diet and sunshine alone.
Of course, such an outcome would make supplement makers happy. Today, coincidentally (?), the drug giant Pfizer announced the launch of “Chocolate Truffle” and “Vanilla Cream” flavored calcium and vitamin D supplements for people who “struggle to get their required daily amount of calcium and vitamin D from food alone.”
Fortunately — for our pocketbooks as well as for our health — that’s one struggle that most Americans are not actually having, as this latest report from the Institute of Health makes clear.