Effect of breast feeding in infancy on blood pressure in later life: systematic review and meta-analysis.(Papers)

Abstract

Objective To determine whether breast feeding in infancy compared with bottle feeding formula milk is associated with lower mean blood pressure at different ages.

Design Systematic review.

Data sources Embase, Medline, and Web of Science databases.

Study selection Studies showing the effects of feeding in infancy on blood pressure at different ages.

Data extraction Pooled mean differences in blood pressure between breast fed infants and those bottle fed formula milk, based on random effects models.

Data synthesis The pooled mean difference in systolic blood pressure was--1.10 mm Hg (95% confidence interval--1.79 to-0.42 mm Hg) but with significant heterogeneity between estimates (P < 0.001). The difference was largest in studies of < 300 participants (-2.05 mm Hg, -3.30 to -0.80 mm Hg), intermediate in studies of 300-1000 participants (1.13 nun Hg, -2.53 to 0.27 mm Hg), and smallest in studies of > 1000 participants (-0.16 mm Hg, -0.60 to 0.28 mm Hg). An Egger test but not Begg test was statistically significant for publication bias. The difference was unaltered by adjustment for current size and was independent of age at measurement of blood pressure and year of birth. Diastolic blood pressure was not significantly related to type of feeding in infancy.

Conclusions Selective publication of small studies with positive findings may have exaggerated claims that breast feeding in infancy reduces systolic blood pressure in later life. The results of larger studies suggest that feeding in infancy has at most a modest effect on blood pressure, which is of limited clinical or public health importance.

Introduction

It has been postulated that nutrition early in life may programme subsequent blood pressure. The influence of breast feeding is of interest because of the differing composition of breast milk and formula milk, particularly the sodium and fatty acid content. Until the 1980s the sodium content of breast milk in Western countries was much lower than that of formula milk. (1 2) Low sodium intake in infancy has been related to lower levels of blood pressure both in the short term and in the long term. (3 4) Long chain polyunsaturated fatty acids are present in breast milk but not in formula milk. These play an important part in the vascular endothelium and, when given as nutritional supplements, seem to reduce blood pressure in adults and children. (5-8)

Small observational studies suggest that breast feeding may be related to noticeably lower blood pressure in childhood. (9-11) Similar conclusions were reached by a follow up study of participants in a randomised controlled trial of feeding in preterm infants. (12) Not all published studies have reported an association. (13) We performed a systematic review to examine whether there are consistent mean differences in blood pressure between adults who were initially breast fed or bottle fed with formula milk.

Methods

We searched Embase, Medline, and Web of Science databases for publications on the effects of feeding in infancy on blood pressure. The electronic search (completed …