Although research has consistently linked high vitamin D levels to improved immune system function, results of a new study suggest that heavy supplementation of vitamin D doesn't reduce diarrheal illnesses among children aged three and younger. The trial, conducted in Kabul, Afghanistan, is described in an article in the journal Pediatrics.
Diarrheal diseases kill 1.8 million children under the age of five every year around the world, according to the World Health Organization.
"It was thought that vitamin D supplementation would help in the prevention of diarrheal illnesses," lead author Dr. Adam Aluisio of the Department of Disease Control at the London School of Hygiene and Tropical Medicine told Reuters Health. "Vitamin D plays a role in the body's defenses against microbes such as viruses and bacteria - we know this from biochemical studies." But there's much more to learn. "We need to know more about how vitamin D supplementation works in the body in relation to disease," he said.
For their study, Aluisio's team extracted data from a trial conducted between 2007 and 2009 that looked at vitamin D's possible effects on childhood pneumonia. During that trial, the researchers also recorded diarrhea incidents. More than 3,000 babies under one year were randomly assigned to one of two groups. The first group received 100,000 international units of vitamin D3 in liquid form once every three months for almost two years. The second group received a placebo. Field workers collected data from participating families twice each week, asking parents whether their child had experienced diarrhea in the previous 24 hours.
There were no differences between the babies who got the vitamin D and those who didn't in the number of diarrhea bouts, the average time until the first bout, or in other factors such as malnutrition and how often mothers washed their hands.
In poor regions, even those with sunny climates like Afghanistan, vitamin D deficiency is a common problem, Dr. Robert Black, director of the Institute for International Programs of Johns Hopkins Bloomberg School of Public Health in Baltimore told Reuters. More than half of Americans are vitamin D deficient.