Is It Time to Give Up on Vitamin D Supplementation in Infancy?

Some studies—both observational and randomized—have teased a potential link between vitamin D deficiency in mothers or infants and later development of atopic diseases. But those results have been inconsistent.

So investigators in Finland performed a large randomized controlled trial (RCT) to, hopefully, definitively answer this question.^[1] Almost 1000 full-term infants were enrolled. The babies were given either 10 µg (400 IU) or 30 µg (1200 IU) daily vitamin D during the first 12 months of life. Concentrations of vitamin D [25(OH)D] were measured during pregnancy, in cord blood at the time of birth, and at 12 months of age.

Infants were evaluated at 1 year of age. Specific IgE antibodies toward common food and airborne allergens were measured. Parents completed questionnaires that asked whether their child had ever received a diagnosis of food allergies, eczema, or asthma or had ever been hospitalized for asthma or bronchiolitis. Additional questions asked about the presence of such symptoms as wheezing, cough, and rash. Finally, the researchers calculated dietary intake of vitamin D on the basis of a food questionnaire.

Over 90% of the infants completed the 12-month follow-up visit. The majority (79%) were breastfed for more than 6 months (average duration, 10.7 months).

Over 95% of the mothers and the infants had appropriate vitamin D levels at the time of birth. Infants in both groups consumed essentially the same amount of vitamin D from food. Not unexpectedly, serum vitamin D concentration was higher in the infants who received the higher dose of daily vitamin D (115 nm/L vs 82.7 nm/L).

But that higher serum level didn't make a difference in the outcome. There were no differences in rates of sensitization to food antigens between the two groups (15.9% of those who received 10 µg of vitamin D per day and 15.6% of those who received 30 µg per day). Similarly, sensitization to airborne allergens was 3.9% among those who received 10 µg of vitamin D per day and 3% among those who received 30 µg, a difference that was not statistically significant.

Allergic sensitization to both allergens was correlated with parental history of allergic disease as well as day care attendance. Duration of breastfeeding, the presence of older siblings, and environmental tobacco smoke exposure were not related to allergic sensitization.

The authors concluded that in infants with sufficient levels of vitamin D, higher supplementation levels of vitamin D did not reduce allergic sensitization to food or airborne allergens, allergic disease, or wheezing during the first 12 months of life.

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This same group of Finnish researchers also concluded previously that higher doses of vitamin D supplementation in infancy have little effect on bone mass or infection risk,^[2] even though these infants living in a northern European population with limited sunlight exposure are exactly the group in whom deficiency might be anticipated.

Two earlier RCTs^[3,4] examined the effects of maternal vitamin D supplementation during pregnancy and similarly found that it did not prevent atopic outcomes in the infants. Another RCT of pregnant women—this one conducted in Bangladesh, where rates of vitamin D deficiency are quite high—found no difference in fetal or infant growth in the women who received high-dose vitamin D from midpregnancy until birth.^[5]

There may be more work still to be done, especially in a population of newborns with known vitamin D deficiency. But at least to this pediatrician, the evidence seems to be mounting that supplementation with vitamin D doesn't promise an easy fix for the high levels of allergic sensitization found in many developed countries.

That is not to say that all vitamin D supplementation is unnecessary. Don't forget that the American Academy of Pediatrics continues to recommend that breastfed and partially breastfed infants be supplemented with 400 IU per day of vitamin D until they are ingesting sufficient amounts of the vitamin from either 1 quart a day of vitamin D-fortified formula or other foods.

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