February 28, 2018

expert reaction to meta-analysis looking at fish oil and probiotic supplements in pregnancy and risk of allergies in children

New research, published in PLOS Medicine, looks at diet during pregnancy and infancy and risk of allergic or autoimmune disease.

Dr Louisa James, British Society for Immunology spokesperson and Lecturer in Immunology at Queen Mary University of London, said:

“Food allergies are increasingly common among infants, particularly those with eczema.  They occur when the immune system reacts inappropriately to various proteins founds in foods.  Our diet and the microbes living in our gut play an important role in building and maintaining a healthy immune system.  Determining how different dietary factors affect the way our immune system works is therefore essential, especially during the early stages of our development, when our immune system is learning how to recognise potential danger.  The results of this study confirm that maternal diet can influence the development of allergies in early life and highlights the pressing need for more research in this area.

“This study reviewed the evidence that maternal diet can influence the risk of allergy development in infants.  The researchers carefully screened the scientific literature to identify studies on maternal and infant diet and pooled the results of similar studies together.  This type of ‘meta-analysis’, that combines data from several studies, can help to identify differences or effects, where they exist, and so are a useful way to evaluate the validity of claims from smaller studies.  The quality of the evidence relies entirely on the quality and size of the available data.  The researchers used stringent criteria to select each study and were careful to check for different factors that could bias the results.  There was not enough evidence from the available studies to conclude if other dietary factors during pregnancy and infancy influence the risk of developing allergies or autoimmune disease; in many cases the number and size of the studies were simply too small or the methods reported were not comparable with each other.

“The studies included in the analysis of probiotic and fish oil supplementation were all randomised controlled trials; the most rigorous way to identify the effects of treatments or interventions.  In all cases the studies only included participants with a high risk of developing allergies so it is unclear what effect probiotics or fish oil supplements would have in families with no history of allergies.  The finding that probiotics may reduce the incidence of eczema is in agreement with similar recent reports although the results of individual studies vary with some finding no evidence of an effect.  The included studies used capsules, powder or liquid supplements but not probiotic yoghurts.  The amount and type of bacteria used in the supplements varies widely among studies making it difficult to conclude which type or dose of bacteria is best.  The studies using fish oil supplementation all measured allergic sensitisation to egg as a surrogate measure of food allergy.  Although sensitisation is necessary for allergies to develop, many children may be sensitised without ever developing any symptoms of allergy and so it will be important to determine if fish oil supplementation can reduce the risk of clinical food allergy.

“This study serves to highlight the value of good quality evidence.  Well-designed studies with sufficient numbers of participants, using appropriate methods of analysis and reporting are essential for developing evidence-based recommendations and guidelines.  While the results of this study are likely to inform the development of guidelines on maternal and infant diet, it seems that there is much more work to be done.  Building on evidence that diet plays an important role in immune health raises the possibility that modifications to our diet, particularly during this critical window in early life, could limit the increasing burden of immune-related disease.”

Prof Seif Shaheen, Professor of Respiratory Epidemiology, Queen Mary University of London, said:

“This is an important, well conducted piece of research, which adds to the growing evidence suggesting that nutrient supplementation during pregnancy and lactation may have the potential to prevent childhood allergy and allergic disease.

“The findings which have been highlighted in this report were obtained by analysing pooled data from multiple randomised clinical trials, and such results are likely to be more reliable than those obtained from observational epidemiological studies.

“The main results can be considered alongside trial data from Denmark suggesting that fish oil supplementation in pregnancy may also prevent wheezing and asthma in the offspring.

“More definitive answers on the possible role of maternal probiotic and fish oil supplementation in the prevention of childhood allergic disease can only come from further large trials, which follow up the children to school age.  If such trials are big enough they may be able to identify particular subgroups of mothers and children who would benefit most from these interventions.”

* ‘Diet during pregnancy and infancy and risk of allergic or autoimmune disease: A systematic review and meta-analysis’ by Vanessa Garcia-Larsen et al. published in PLOS Medicine on Wednesday 28 February 2018. 

Declared interests

Dr Louisa James: “No conflict of interest to declare.”

Prof Seif Shaheen: “No conflicts of interest to declare (I collaborated with the lead author many years ago).”