Fish oil supplementation in pregnancy results in increased weight, but not obesity, in childhood
Supplementation with fish oil from the 24th week of pregnancy leads to a higher body mass index (BMI) in the first 6 years of life in offspring but not an increased risk of overweight or obesity, suggests a study.
“The n-3 LCPUFA (long chain polyunsaturated fatty acids) supplementation resulted in a proportional increase in lean mass, bone mass and fat mass, suggesting that n-3 LCPUFA supplementation in the third trimester of pregnancy stimulates healthy somatic growth to age 6 years,” researchers said.
Participants in the fish oil supplementation vs the control group showed increased BMI z score between age 0 and 6 years (0.14; 95 percent CI, 0.04–0.23; p=0.006). At 6 years, supplementation resulted in a higher BMI z score (0.19; 0.06–0.32; p=0.004), a higher weight/height (3.48 g/cm; 0.38–6.57; p=0.03) and a larger waist circumference (0.6 cm; 0.0–1.2; p=0.04) but not a higher proportion of obese children, using International Obesity Task Force grades. [BMJ 2018;362:k3312]
The supplementation group showed a higher total mass (395.4 g; 86.6–704.3; p=0.01) in the dual energy x ray absorptiometry scan compared with that in the control group at age 6 years, characterized by a higher lean mass (280.7 g; 98.9–462.4; p=0.002), a higher bone mineral content (10.3 g; 2.3–18.1; p=0.01) and a nonsignificantly higher fat mass (116.3 g; –92.9 to 325.5; p=0.28). However, there were no differences in total body fat or lean mass percentage.
In previous trials and systematic reviews, n-3 LCPUFA supplementation during pregnancy and/or lactation showed no effect on BMI or growth development in childhood. [Am J Clin Nutr 2016;103:1489-1496; Br J Nutr 2016;116:2082-2090; Pediatrics 2008;122:e472-479; Eur J Clin Nutr 2014;68:1277-1287; Cochrane Database Syst Rev 2015;7:CD007901]
“Potential explanations for the discrepancy between our findings and previous studies include differences in the dose and type of n-3 LCPUFA supplied, the timing of the supplementation, the trial design and the accuracy of measurements,” researchers said.
In another trial, supplementation with 1.5 g n-3 LCPUFA during the first 4 months led to a significantly higher BMI and increased waist circumference in the offspring at 2.5 years. However, no differences were observed at 7 or 13 years of age. [J Perinat Med 2012;40:677-684; Br J Nutr 2016;116:2082-2090]
Furthermore, the BMI development curves and the significant interaction with age indicated that the effect of n-3 LCPUFA supplementation on BMI was most prominent after age 1 year. Early onset of peak BMI in infancy, occurring usually at age 6 months, has been associated with later obesity risk. [Horm Res 2006;65(Suppl 3):65-69]
“The lack of an effect of n-3 LCPUFA in the first year of life in our trial could therefore reflect that n-3 LCPUFA supplementation has a general growth stimulating effect, which does not increase the risk of overweight or obesity,” researchers said.
The present study included 736 pregnant women and their offspring, who were randomized to receive n-3 LCPUFA or olive oil (control) from pregnancy week 24 until 1 week after birth. Measured outcomes included height/length, weight, head, and waist measurements and body composition from dual energy x ray absorptiometry (all prespecified secondary endpoints of the n-3 LCPUFA trial; the primary outcome for the trial was persistent wheeze/asthma).