[pronut-hiv] Milk, Vitamin D Intake During Pregnancy Linked to Infant Birth Weight

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Milk, Vitamin D Intake During Pregnancy Linked to Infant Birth Weight

April 27, 2006 — Milk and vitamin D intake during pregnancy are independently associated with infant birth weight, according to the results of a study reported in the April 25 Online First issue of CMAJ.

"Some pregnant women may be advised or choose to restrict milk consumption and may not take appropriate supplements," write Cynthia A. Mannion, MD, from McGill University in Ste. Anne de Bellevue, Quebec, and colleagues. "We hypothesized that maternal milk restriction during pregnancy, which can reduce intakes of protein, calcium, riboflavin and vitamin D, might represent a health risk by lowering infant birth weight."

At prenatal programs in Calgary, Alberta, the investigators screened women between the ages of 19 and 45 years for low milk consumption (</= 250 mL/day), and using repeat dietary recalls, they compared these women and their newborns with women whose milk consumption was greater than 250 mL (1 cup) daily. Birth records provided data on birth weight, length, and head circumference.

Compared with women who consumed more than 250 mL/day of milk (n = 207), those who consumed 250 mL/day or less of milk (n = 72) gave birth to infants of lower weight (3410 vs 3530 g; P = .07). However, infant lengths and head circumferences were similar in both groups. Women with low milk intake also had statistically significantly lower intakes of protein and vitamin D.

Multivariate analyses controlled for previously established predictors of infant birth weight revealed that both milk consumption and vitamin D intake were significant predictors of birth weight. Each additional cup of milk per day was associated with a 41-g increase in birth weight (95% confidence interval [CI], 14.0 - 75.1 g), and each additional microgram of vitamin D was associated with an 11-g increase in birth weight (95% CI, 1.2 - 20.7 g). Protein, riboflavin, and calcium intake were not significant predictors of birth weight.

"Milk and vitamin D intakes during pregnancy are each associated with infant birth weight, independently of other risk factors," the authors write. "Restricting fortified milk or vitamin D intake during pregnancy lowered infant birth weight in otherwise healthy, nonsmoking, well-educated mothers. This is an important finding because increasing numbers of women are restricting milk consumption during pregnancy, believing that it will lower fat intake, minimize weight gain, treat self-diagnosed lactose intolerance or prevent their children from developing allergies."

Study limitations include participation of only 24% of women who reported restricting milk consumption and lack of maternal or infant blood samples for measurements of vitamin D.

"Current recommendations to restrict intake of fortified milk are clearly ill-advised for those living at latitudes where dermal conversion of 7-dehydrocholecalciferol to active vitamin D is seasonally limited," the authors conclude. "Fortified milk provides an important source of vitamin D and calcium, and contributes to adequate protein intake. Practitioners should query pregnant women about their consumption of fortified milk and multivitamins, specifically those containing vitamin D, to avoid the risk of lowered birth weight as a result of insufficient intake, particularly when and where sun exposure is limited."

The Dairy Farmers of Canada and FRSQ, Fonds de recherche en Sant* du Qu*bec, funded this study.

In an accompanying comment, Bruce W. Hollis, MD, and Carol L. Wagner, MD, from the Medical University of South Carolina in Charleston and colleagues, call this "a very intriguing and important observation." Their group is studying vitamin D supplementation of up to 4000 IU of vitamin D3 per day during pregnancy in a multiyear, double-blinded, placebo-controlled trial.

"Why are these studies essential?" Drs. Hollis and Wagner write. "We believe that they are important to determine the true vitamin D requirement during pregnancy not only for maternal skeletal preservation and fetal skeletal formation, but also for fetal 'imprinting' that may affect neurodevelopment, immune function and chronic disease susceptibility later in life as well as soon after birth."

Dr Hollis has disclosed that he received consultancy fees from DiaSor Corp in Stillwater, Minn.

CMAJ. Posted online April 25, 2006.