Probiotics linked to reduced eczema risk; fish oil to lower risk of egg allergy
Probiotics during pregnancy may reduce the risk of eczema in offspring, while fish oil supplementation may reduce the risk of potential egg allergy, a systematic review and meta-analysis found.
Nineteen trials suggested that maternal supplementation with probiotics taken during late pregnancy and lactation was associated with a reduced risk of eczema at ages ≤4 years (RR 0.78, 95% CI 0.68-0.90, I2=61%), reported Vanessa Garcia-Larsen, PhD, of the Johns Hopkins School of Public Health in Baltimore, and colleagues.
Moreover, six trials suggested that fish oil supplementation during pregnancy and lactation may be linked to a reduced risk of allergic sensitization to egg (RR 0.69, 95% CI 0.53-0.90, I2=15%), the authors wrote in PLoS Medicine.
They noted that while there is evidence that early dietary exposures could influence the development of immune-mediated health conditions, such as allergic and autoimmune diseases, “a comprehensive analysis of the relationship between all dietary exposures during pregnancy, lactation, or the first year of life” and risk of these diseases has not been undertaken.
Garcia-Larsen’s group also stated that while a World Allergy Organization guidelinerecommends prebiotic and probiotic supplements to prevent eczema, European, North American and Australian guidelines “do not support this.” Certain guidelines recommendexclusive breastfeeding for the first 4 to 6 months of life to reduce risk of eczema, food allergy, and wheezing, while recent Australasian guidelines recommended “oily fish or omega-3 fatty acid supplements during pregnancy” to reduce eczema.
“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,” said co-author Robert Boyle, MD, of Imperial College London, in a statement.
This evidence review was conducted to inform U.K. dietary recommendations for infants and their pregnant or lactating mothers, the authors said. They examined 260 studies about milk feeding, including one on breastfeeding promotion, and 173 studies of “other maternal or infant dietary exposures,” which included 80 trials of maternal, infant, or combined interventions.
The researchers found a high risk of bias in nearly half of the milk feeding studies and a quarter of studies on other dietary exposures. They noted this was due to “attrition bias in intervention studies and confounding bias in observational studies.” Findings of these studies were evaluated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system of evidence.
Probiotic and prebiotic supplementation studies evaluated single or multiple organisms, given as capsules, powder, or part of a drink or infant formula milk at a dose of 1 to 10 billion colony-forming units per day. When examining the link between supplementation with probiotics during late pregnancy and lactation and risk of eczema, the absolute risk reduction was 44 cases per 1,000 (95% CI 20-64). The absolute risk reduction was 31 cases per 1,000 (95% CI 10-47) when examining the association between fish oil supplementation during pregnancy and lactation and risk of allergic sensitization to egg. GRADE certainty of these findings was moderate, the authors said.
But GRADE certainty of findings was low for other findings, such as:
- Breastfeeding promotion reducing risk of eczema during infancy (one intervention trial)
- Longer exclusive breastfeeding reducing type 1 diabetes mellitus (28 observational studies)
- Probiotics reducing allergic sensitization to cow’s milk (nine observational studies)
Study limitations included that for many dietary exposures, evidence was inconclusive or inconsistent, so the authors were unable to “exclude the possibility of beneficial or harmful effects.” They also cited that their search date for observational studies was 2013, so this information “may benefit from an update.” They noted that they included abstract publications, since their exclusion can lead to publication bias, but there may be methodological bias due to lack of peer review.
“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,” Garcia-Larsen said in a statement. “This study has provided clues, which we now need to follow with further research.”
This study was supported by grants from the U.K. Food Standards Agency.
Garcia-Larsen disclosed support from the U.K. Food Standards Agency.
Other co-authors disclosed support from the U.K. Food Standards Agency and one co-author was a co-investigator and author of two of the trials included in this systematic review.