Low Maternal Vitamin D May Lead to Higher Body Fat in Kids

Larry Hand

May 25, 2012

May 25, 2012 — Children may be more prone to have excess body fat at age 6 years if their mothers had low vitamin D levels during pregnancy, according to a study published online May 23 in the American Journal of Clinical Nutrition.

Sarah R. Crozier, PhD, from the Medical Research Council Lifecourse Epidemiology Unit (MRC LEU), University of Southampton, United Kingdom, and colleagues conducted a study of 977 pregnant women aged between 20 and 34 years old and their children who were enrolled in the Southampton Women's Survey (SWS) between April 1998 and December 2002. During the original study period, research nurses obtained blood samples and recorded serum 25-hydroxyvitamin D [25(OH)D] concentrations at about 35 weeks' gestation.

Although a total of 1981 women in the SWS became pregnant, only 977 women and children were included in this new study because 977 children had acceptable whole-body dual-energy X-ray absorptiometry (DXA) scans to measure body composition at birth and at ages 4 and 6 years.

In an unadjusted analysis, Dr. Crozier and colleagues found that lower vitamin D status for the pregnant women was associated with greater fat mass in the children at ages 4 and 6 years, but not at birth. However, after adjustments for several factors, including mother's education, smoking in pregnancy, body mass index, and social class, they saw a positive relationship between vitamin D levels and fat mass at birth (P = .02), as well as the negative association for vitamin D during pregnancy and child fat mass at age 6 years.

Compared with women with low vitamin D (≤50 nmol/L), fat mass for children at birth was "8% (95% [confidence interval (CI)]: 1%, 16%) greater among those born to mothers whose 25(OH)D concentrations were between 50 and 75 nmol/L, and 10% (95% CI: 3%, 17%) greater among those whose mothers had a 25(OH)D concentration >75 nmol/L," the researchers write.

In addition, fat mass at age 6 years was "8% (95% CI: 2%, 14%) lower among mothers who had a vitamin D status between 50 and 75 nmol/L, and 6% (95% CI: 0, 12%) lower among mothers who had a vitamin D status >75 nmol/L," they write.

Modeling the data showed a threshold of about 64 nmol/L of maternal vitamin D associated with adiposity at age 6 years, after adjustments. For mothers whose serum concentrations were lower, results showed a significant association with higher fat mass at age 6 years (β, −0.24; 95% CI, −0.41 to −0.07; P = .006). For mothers whose serum levels were higher, results showed no association (β, 0.00; 95% CI, −0.19 to −0.18; P = .99).

A weakness of the study may have been that DXA measures were unavailable for the entire SWS population, and that this subset of women had better education, were less likely to smoke during pregnancy, and were older, taller, and more likely to be white. However, the researchers write that they believe it was unlikely that selection bias affected the results.

Mechanisms that link maternal vitamin D insufficiency to child adiposity are unknown, the researchers note, and further studies are needed. However, they add, "the present findings add weight to current concerns about the prevalence of low vitamin D status among women of reproductive age."

They conclude, "One interpretation of our data is that there are programmed effects on the fetus that arise from maternal vitamin D insufficiency that remain with the individual and that may predispose him or her to gain excess body fat in later childhood."

In a press release, Professor Cyrus Cooper, MA, DM, FRCP, FFPH, FMedSci, director of the MRC LEU, said: "The observations that maternal vitamin D insufficiency might be associated with reduced size at birth, but accelerated gain in body fat during early childhood, add to the considerable amount of evidence suggesting that vitamin D status during pregnancy may have critical effects on the later health of offspring."

The study was supported by the Medical Research Council, the British Heart Foundation, the Food Standards Agency, and Arthritis Research United Kingdom. One study author is supported by the National Institute for Health Research (NIHR) through the Southampton NIHR Biomedical Research Unit in Nutrition, Diet, and Lifestyle. That same author has acted as a consultant to Abbott Nutrition and Nestlé Nutrition and has received reimbursement for speaking at an Abbott Nutrition Conference on Pregnancy Nutrition and Later Health Outcomes and at a Nestlé Nutrition Institute Workshop; he is also part of an academic consortium that has received research funding from Abbott Nutrition, Nestec, and Danone. The other authors have disclosed no relevant financial relationships.

Am J Clin Nutr. Published online May 23, 2012. Abstract