SAN FRANCISCO – The Institute of Medicine will change its recommended level of vitamin D intake for children on Nov. 30, 2010, predicted Dr. Russell Chesney, professor and chairman of pediatrics at the University of Tennessee Health Science Center in Memphis.
The change, presumably an increase, comes not a moment too soon, said Dr. Chesney, who cited a long list of potential health benefits for the substance. "Vitamin D truly is the center of the universe," he joked.
Dr. Russell Chesney
Among the conditions that vitamin D may ameliorate include infectious diseases, ovarian cancer, multiple sclerosis, rheumatoid arthritis, inflammatory bowel syndrome, wheezing, diabetes types 1 and 2, hypertension, atherosclerosis, colorectal cancer, prostate cancer, and breast cancer. "Wow, where has this stuff been all these years?" he said, drawing laughter from the plenary session audience at the annual meeting of the American Academy of Pediatrics.
Actually, vitamin D supplementation dates back to the days when mothers spooned cod-liver oil into their children's mouths. This form of the supplement proved effective in preventing and treating rickets.
Since then, evidence has mounted for other benefits. Most claims are based on epidemiological studies. For example, people who live at higher altitudes and get more sunshine exposure – which causes vitamin D synthesis – may suffer less from tuberculosis. "Our ancestors were right when they said we should go to sanatoriums in the mountains," said Dr. Chesney.
He added that prospective trials are still needed. "This is suspected. This is not proven."
But a few small studies have already reinforced such findings. In one recent study that Dr. Chesney described, a group of 167 Japanese children took supplements of 1,200 IU of vitamin D, while another group of 167 took a placebo. Those who took the vitamin D had half the influenza incidence of the placebo group, as well as fewer attacks of asthma.
How can one vitamin produce such benefits? Actually, D is not a vitamin but a hormone – strictly speaking, a secosteroid, Dr. Chesney said. It influences the promoter regions of several genes and is involved in the transcription of some 300 proteins and peptides.
Among the peptides it helps produce is LL-37 cathelicidin, which kills Mycobacterium tuberculosis and Escherichia coli.
Other research suggests that vitamin D inhibits proinflammatory and autoimmune cytokines and promotes those that are anti-inflammatory, said Dr. Chesney.
So many claims of benefits for one vitamin may sound exaggerated, he acknowledged, harkening back to the excitement over vitamin E a couple of decades ago. But it's also true that vitamin D levels are declining in the United States as Americans spend more time indoors and take precautions to avoid skin cancer. "Kids these days are on house arrest," he said, echoing Richard Louv’s keynote address on "nature deficit disorder" earlier in the meeting.
"This is not an advertisement for all of us to go out to the beach," said Dr. Chesney. "But it is a point that we are not getting as much sunshine as a society as we used to, and in that case we may need to get supplementation."
How much supplementation? That's still being debated. That teaspoon of cod-liver oil contained about 400 IU, and that's the same daily dose that the American Academy of Pediatrics has been recommending since 2008. The AAP advises supplementing with 400 IU of vitamin D for breast-fed infants and older children who are not getting at least that much through their diet.
"What led to this recommendation?" he asked. "There was growing concern that the Institute of Medicine's recommended intake of 200 IU/day [for everyone younger than 51 years of age] was not adequate. Vitamin D may be one of the only substances whose dose is lower than the RDA [recommended daily allowance]. Numerous groups have called on the institute to update their recommendation, and they are going to do so."
While there is also debate about serum levels of vitamin D (serum 25-hydroxyvitamin D), Dr. Chesney said anything below 11 ng/mL is "clearly deficient." He called 11-20 ng/mL "insufficient," and said that less than 30 ng/mL is "probably on the lower end of sufficient." (In nmol/L, those cutoffs would be 27.5, 50, and 75.)
Supplements are quite safe, he added. "The lowest observed side effects [occur at] more than 4,000 IU/day and probably more like 10,000 IU/day," he said. "The tolerable upper limit in a child is set at 1,000 IU, but you could probably go higher."
Reflecting on the country's long history of vitamin D supplementation, Dr. Chesney finished by quoting Ecclesiastes 1:9, "There is nothing new under the sun."