The systematic review and meta-analysis, published in PLOS Medicine, was commissioned by the UK's Food Standards Agency (FSA) and pooled data from more than 400 studies involving around 1.5 million people. It is one of the largest ever investigations into the impact of maternal diet on their children’s allergy and eczema risk.
Pregnant women who took fish oil supplements from 20 weeks pregnant up until the third or fourth month of breastfeeding, reduced their infant’s risk of egg allergy by 31% by age one, found the research team from Imperial College, London.
This corresponds to 31 cases per 1000 children in terms of absolute risk reduction, the researchers noted.
Fish oil supplementation also decreased the risk of peanut allergies by 38%. However, only two studies were found which examined this outcome.
Pregnant women consuming probiotics reduced their offspring’s risk of atopic eczema by 22% up to age 4, equating to 44 cases per 1000 children. Some risk reduction was also seen with prebiotics, but the results were not statistically significant.
"Our research suggests probiotic and fish oil supplements may reduce a child's risk of developing an allergic condition, and these findings need to be considered when guidelines for pregnant women are updated," commented Professor Robert Boyle, lead author of the research from the Department of Medicine at Imperial College London.
"Food allergies and eczema in children are a growing problem across the world. Although there has been a suggestion that what a woman eats during pregnancy may affect her baby's risk of developing allergies or eczema, until now there has never been such a comprehensive analysis of the data," said Boyle.
Maternal avoidance of allergenic foods during, such as nuts, egg, milk or wheat did not have an effect on the child’s risk of allergy or autoimmune disease, the scientists found.
Timing of fish oil supplementation may be important. Subgroup analysis found that reduction in egg allergy risk was 45% in the offspring of mothers who consumed them during pregnancy, but only a non-significant 8% for supplements taken during breastfeeding only. (There were however a limited number of studies reporting on this aspect).
Although omega-3 polyunsaturated fatty acids (PUFAs) from fish oil provided a benefit, omega-6 PUFAs did not.
The researchers also found some evidence of an association between longer duration of breastfeeding and lower eczema risk, and that exclusive breastfeeding was linked with lower type-1 diabetes risk.
No association was found between consuming supplements of any kind and development of other autoimmune diseases.
Probiotic species and dose
In studies where probiotics provided a beneficial effect, the species Lactobacillus rhamnosus was frequently present. Doses between 1 and 10 billion colony forming units (CFU) were found to be effective.
“A daily probiotic supplement such as L. rhamnosus, taken from around 36 to 38 weeks gestation through the first 3 to 6 months of lactation, may reduce risk of eczema in the child,” recommended the researchers. However, use of this species should be avoided earlier in pregnancy, the researchers cautioned.
Although the beneficial effects from fish oil may be due to the anti-inflammatory properties of omega-3 PUFAs, identifying the anti-allergic mechanism of action (MOA) needs further research, together with establishing an MOA for probiotics.
"Despite allergies and eczema being on the rise, and affecting millions of children, we are still hunting for the root causes of these conditions, and how to prevent them," said Professor Vanessa Garcia-Larsen, co-author of the study.
"This study has provided clues, which we now need to follow with further research," she added.
The Government is examining the findings of this FSA-funded study together with the wider evidence base on infant feeding and the introduction of solids. The risks and benefits associated with the timing of introduction of allergenic foods will also be considered as part of a cross-party review.
“These findings suggest that current infant feeding guidance needs revision. Guideline committees will need to carefully consider the key findings together with an evaluation of the safety, acceptability, and cost implications of advising probiotic or fish oil supplementation for pregnant and lactating women,” the researchers concluded.
Source: PLOS Medicine
Volume 15, issue 2: e1002507. DOI: 10.1371/journal.pmed.1002507
“Diet during pregnancy and infancy and risk of allergic or autoimmune disease: A systematic review and meta-analysis”
Authors: Vanessa Garcia-Larsen, Robert J. Boyle