For kids who get a lot of colds during the winter, a boost in vitamin D levels may be just what the doctor ordered, researchers reported Monday. Supplementing vitamin D intake for children who were deficient halved the number of colds the children contracted, a team reported in the journal Pediatrics.
Observational studies have suggested that low vitamin D levels are associated with an increased risk of colds. The new study is apparently the first to show that supplementing children's intake of the vitamin can reduce their risk of colds.
Dr. Carlos A. Camargo Jr. of Massachusetts General Hospital in Boston and his colleagues studied 247 third- and fourth-graders in Ulaanbaatar, Mongolia, as part of a larger study called the Blue Sky Study. They picked the city because the combination of an extremely cold climate and the high latitude restricts the amount of time children play outside in the sun. Sun shining on the skin is a major source of vitamin D. Moreover, foods and milk in Mongolia are not routinely supplemented with vitamin D.
At the beginning of the study, the children had an average vitamin D level in their blood of about 7 nanograms per milliliter (ng/ml). Any level below 20 ng/ml is considered a deficiency. About half of the children (104) received normal milk with no vitamin D and the rest received daily milk fortified with 300 international units (IU) of vitamin D. After three months, blood levels of the vitamin in the control group were unchanged, while the level in the group who received supplements rose to an average of 19 ng/ml. At the end of the three months, the children's parents were interviewed about the incidence of upper respiratory infections -- that is, colds. The children who received vitamin D supplements had 50% fewer colds.