Effect of fish oil supplementation in pregnancy on bone, lean, and fat mass at six years: randomised clinical trial

Abstract

Objective: To examine the effect of supplementation with n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) in pregnancy on anthropometry and body composition in offspring.

Design: Double blinded, randomised controlled trial.

Setting: Copenhagen Prospective Studies on Asthma in Childhood2010 cohort.

Participants: 736 pregnant women and their offspring.

Intervention: n-3 LCPUFA (fish oil) or control (olive oil) daily from pregnancy week 24 until one week after birth.

Main outcome measures: Height/length, weight, head, and waist measurements and body composition from dual energy x ray absorptiometry (all pre-specified secondary endpoints of the n-3 LCPUFA trial; the primary outcome for the trial was persistent wheeze/asthma).

Results: The mean body mass index (BMI) z score was increased between age 0 and 6 years in the fish oil supplementation group compared with the control group (0.14 (95% confidence interval 0.04 to 0.23); P=0.006). At 6 years, supplementation was associated with a higher BMI z score (0.19 (0.06 to 0.32); P=0.004), a higher weight/height (3.48 (0.38 to 6.57) g/cm; P=0.03), and a larger waist circumference (0.6 (0.0 to 1.2) cm; P=0.04) but not a higher proportion of obese children, using International Obesity Task Force grades. The dual energy x ray absorptiometry scan at age 6 years showed a higher total mass (395.4 (86.6 to 704.3) g; P=0.01) in the supplementation versus the control group, explained by a higher lean mass (280.7 (98.9 to 462.4) g; P=0.002), a higher bone mineral content (10.3 (2.3 to 18.1) g; P=0.01), and a non-significantly higher fat mass (116.3 (-92.9 to 325.5) g; P=0.28), but no differences were seen in total body fat or lean mass percentage.

Conclusion: Fish oil supplementation from the 24th week of pregnancy led to a higher BMI in the offspring from 0 to 6 years of age but not an increased risk of obesity at age 6. The body composition at age 6 years in children given fish oil supplementation was characterised by a proportional increase in lean, bone, and fat mass suggesting a general growth stimulating effect of n-3 LCPUFA.

Trial registration: Clinicaltrials.gov NCT00798226.

Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work other than that described above; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Figures

Fig 1

Top: curves showing mean body mass index (BMI) according to visit age for children in n-3 long chain polyunsaturated fatty acid (n-3 LCPUFA) supplementation group and control group up to age 6 years. Bottom: effects of n-3 LCPUFA supplementation on BMI through infancy and childhood, illustrated by mean difference in BMI z score at each visit and 95% confidence intervals

Fig 2

Density plot showing lean mass, bone mass, and fat mass stratified by supplementation groups: n-3 long chain polyunsaturated fatty acid (n-3 LCPUFA) and control. Lean mass and fat mass are adjusted for (height+height^2); g/cm+cm^2. Bone mass is adjusted for height; g/cm.