Vitamin D supplementation cuts childhood colds and flu in half
A report published online on August 20, 2012 in the journal Pediatrics reveals a dramatic decrease in the incidence of wintertime acute respiratory tract infections (ARIs) in children supplemented with vitamin D. Although observational studies have associated a lower risk of the infections with higher vitamin D levels, the investigation is one of the first randomized, double-blinded trials to study the effects of vitamin D supplementation on childhood ARI.
The trial included 247 children residing in Mongolia, which receives limited winter sunlight. Participants had a median serum 25-hydroxyvitamin D concentration of 7 nanograms per milliliter (ng/mL) at the beginning of the study (a deficient level associated with reduced sunlight exposure). One hundred forty-three children received milk fortified with 300 international units (IU) vitamin D per day and 104 subjects received unfortified milk for seven weeks beginning in late January.
At the trial’s conclusion, vitamin D levels increased to a median of 19 ng/mL among those who received vitamin D fortified milk while remaining the same among the control group. Parents of subjects who received vitamin D reported 48 percent fewer respiratory infections in their children over the course of the study compared with those whose children did not receive the vitamin. Adjustment for age and other factors resulted in a similar, 50 percent lower risk in the supplemented group.
“Our randomized controlled trial shows that vitamin D has important effects on infection risk,” stated first author and Harvard Medical School professor of Medicine Carlos Camargo, MD. “In almost 250 children with low blood levels of vitamin D during winter, we found that taking a daily vitamin D supplement cut in half the risk of a respiratory infection.”
“Our study design provides strong evidence that the association between low vitamin D and respiratory infections is causal and that treating low vitamin D levels in children with an inexpensive and safe supplement will prevent some respiratory infections,” he added. “The large benefit was undoubtedly related to the low baseline vitamin D levels of these children, so I would not expect the supplement to provide similar benefit in children who start with healthy levels of vitamin D. The key question for future research is at what initial vitamin D level would children no longer receive benefit from winter supplementation?”
“At the time the trial was designed, the Institute of Medicine recommended 200 IU daily for all individuals from birth to age 50 years,” the authors write. “The 2011 Institute of Medicine report has since increased the recommendation to 400 IU daily for children. Although this higher dose is certainly an improvement, we suspect that even 400 IU daily will fall short for many children with vitamin D deficiency. Other groups, such as the Canadian Paediatric Society, recommend 1000 IU daily for children, and we believe that this higher dose is more likely to achieve adequate 25-hydroxyvitamin D levels for almost all children without pushing them to a potentially toxic level.”
Studies support association of higher vitamin D levels with disease risk reduction
The results of two studies conducted by Intermountain Medical Center Heart Institute in Murray Utah, presented on March 15, 2010 at the American College of Cardiology’s 59th annual scientific session in Atlanta, show that individuals who increase their vitamin D levels experience a lower risk of cardiovascular disease, heart attack, heart failure, high blood pressure, diabetes, depression, kidney failure and all-cause mortality over a given period of time.
The first study included 9,491 participants in whom low vitamin D levels of 30 nanograms per milliliter (considered “normal” by some practitioners) or less were detected. Nearly 80 percent of the subjects were women. Among the 47 percent who increased their vitamin D levels to 30 nanograms per milliliter or more between their initial and follow-up examinations, there was a decrease in the risk of coronary artery disease, heart failure, renal failure and death compared with those whose vitamin D levels failed to reach this level.
In the second study, the disease-predictive value of varying levels of vitamin D in 31,289 subjects aged 50 and older was analyzed. The researchers concluded that having a vitamin D level of greater than 43 nanograms per milliliter was optimal to significantly lower the risk of seven out of ten outcomes during the period examined: death, diabetes, coronary artery disease, myocardial infarction, heart failure, depression and renal failure.
“It was very important to discover that the ‘normal’ levels are too low,” noted research team member Dr Heidi T. May. “Giving physicians a higher level to look for gives them one more tool in identifying patients at-risk and offering them better treatment.”
“Vitamin D replacement therapy has long been associated with reducing the risk of fractures and diseases of the bone,” noted Joseph Brent Muhlestein, MD, who is the director of cardiovascular research at the Intermountain Medical Center Heart Institute and co-researcher in both studies. “But our findings show that vitamin D could have far greater implications in the treatment and reduction of cardiovascular disease and other chronic conditions than we previously thought.”
Dr Muhlestein remarked that increasing vitamin D intake by supplementing with 1,000 to 5,000 international units per day may be appropriate for some people.
“Although randomized trials would be useful and are coming, I feel there is enough information here for me to start treatment based on these findings,” he added.
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