Maternal fish oil supplementation tied to overweight in children

Children of mothers who took n‒3 long-chain polyunsaturated fatty acid (LCPUFA) supplements during pregnancy tend to have an increased body mass index (BMI) at age 10 years, a higher risk of being overweight, and greater fat percentage and metabolic syndrome score, a study has shown.

“These findings suggest potential adverse health effects from n–3 LCPUFA supplementation during pregnancy and need to be replicated in future independent studies,” said the investigators, led by Rebecca K Vinding from the Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.

Vinding and her team performed a follow-up analysis of a randomized clinical trial done on 736 pregnant women and their children who participated in the Copenhagen Prospective Studies on Asthma in Childhood mother-child cohort. Participants received 2.4 g n‒3 LCPUFA or control daily from pregnancy week 24 until 1 week after birth.

The following outcomes were analysed: anthropometric measurements, body composition from Bioelectrical Impedance Analysis, blood pressure, concentration of triglycerides, cholesterol, glucose, and C-peptide from fasting blood samples. The investigators also calculated a metabolic syndrome score.

Children whose mothers received n‒3 LCPUFA supplementation showed a higher mean BMI at 10 years of age than those in the control group (17.4 vs 16.9 kg/m²; p=0.020), as well as a higher likelihood of being overweight (odds ratio, 1.53, 95 percent confidence interval [CI], 1.01‒2.33; p=0.047). [Am J Clin Nutr 2024;119:960-968]

This resulted in differences in body composition with respect to increased lean mass (0.49 kg, 95 percent CI, ‒0.20 to 1.14; p=0.17), fat mass (0.49 kg, 95 percent CI, ‒0.03 to 1.01; p=0.06), and fat percent (0.74 percent, 95 percent CI, ‒0.01 to 1.49; p=0.053) relative to controls.

In addition, children of mothers receiving n‒3 LCPUFA showed a higher metabolic syndrome score than their counterparts in the control group (mean difference, 0.19, 95 percent CI, ‒0.02 to 0.39; p=0.053).

Potential mechanisms

The investigators set out to determine the possible mechanisms driving the difference in metabolic health between the two intervention groups by analysing activity level, eating habits, and puberty stage. [Cochrane Database Syst Rev 2005;3:1-70; Int J Obes Relat Metab Disord 1992;16:355-360]

“Overall, we found no difference in daily activity or amount of activity, although we found a nonsignificant association whereby children in the n–3 LCPUFA group spent less time on light activity than children in the control group,” Vinding said.

“This could be a random finding, also taking multiple tests into account, and we found no evidence that the difference in light activity level mediated the effect of n–3 LCPUFA supplementation on BMI or body composition,” she added.

Additionally, no difference was noted in the eating habits between the two groups, indicating that such factor was not the reason for the differences seen in anthropometric measurements. Likewise, differences in pubertal development did not drive these disparities.

“It is … possible that our findings of increased BMI, risk of being overweight, and a potentially increased metabolic syndrome score are spurious, eg, the result of randomly increased prevalence of children with a tendency to be overweight in the treatment group, which then persists into older ages and is also reflected in associated traits, such as the metabolic syndrome score,” Vinding said.

“However, the fact that we found no differences in baseline characteristics both in relation to our drop-out analysis and between the intervention groups at 10 years of age suggests that our findings are not because of selection or attrition bias,” she added.