Vitamin D in pregnancy may reduce childhood wheeze

NEW YORK (Reuters Health) - High levels of vitamin D, obtained through the diet or through supplements, during pregnancy appear to reduce the risk of recurrent wheeze or wheeze symptoms in early childhood, according to the findings of two studies reported in the American Journal of Clinical Nutrition.

In the first study, Dr. Carlos A. Camargo, from Massachusetts General Hospital in Boston, and colleagues used a food questionnaire to assess vitamin D levels during pregnancy and then correlated these findings with recurrent wheeze in the child at 3 years of age. A total of 1,194 mother-child pairs were included in the analysis.

The average total vitamin D level during pregnancy was 548 IU per day. Recurrent wheeze was identified in 186 children, the report indicates.

Mothers in the top 25 percent of vitamin D were 61-percent less likely to have a child with recurrent wheeze compared with those in the lowest 25 percent.

For each 100-IU increase in vitamin D, the risk of having a child with recurrent wheeze fell by 19 percent.

This benefit was noted whether the vitamin D came from supplements or the diet.

If others duplicate these findings, the researchers suggest that randomized trials of vitamin D repletion in populations at high-risk of asthma and asthma mortality be performed.

In the second study, Dr. Augusto A. Litonjua, from the Channing Laboratory in Boston, and colleagues examined the impact of maternal vitamin D intake on childhood wheezing symptoms at 5 years of age. This study involved 1212 mother-child pairs.

Compared with the group with the lowest vitamin D levels, women with the highest levels of vitamin D had a 52-percent reduced risk of wheeze and a 65-percent reduced risk of wheeze in the previous year. Vitamin D levels were also associated with reductions in bronchodilator response, which is aggravated in asthma.

"Our results are of great public health significance because they could lead to relatively low cost interventions of vitamin D supplementation that would have a large effect on the future prevalence of asthma in children," the researchers conclude.

SOURCE: American Journal of Clinical Nutrition, March 2007.