Major analysis is being considered by UK government to inform future dietary guidelines for expectant mothers.
Fish oil supplements and probiotic yoghurts during pregnancy may decrease children’s risk of developing allergies, a major evidence review has found.
The study on how childhood allergies are influenced by mothers’ diet also found that avoiding key foods like peanuts, eggs and dairy had little impact on future allergies or eczema.
The findings are now being considered by the British Government and could influence new dietary guidance for expectant mothers and infants.
“Food allergies and eczema in children are a growing problem across the world,” said lead author Dr Robert Boyle from the Department of Medicine at Imperial College London.
“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.
“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.”
Food allergies affect around one in 20 children in the UK.
These are caused by the immune system becoming sensitive to harmless chemicals in foods like peanuts or dairy and over-reacting. Then this triggers the body’s defence response that includes rashes swelling, and the closing off of the airways.
Eczema, a condition causing cracked, dry and itchy skin, affects 20 per cent of UK children. It is also linked to children having a higher risk of food allergies, although it’s not clear why.
The Imperial team reviewed over 400 studies, covering 1.5 million people, on the link between maternal diet, allergies and breast feeding, for the research – which is published in PLOS Medicine. It was funded by the Food Standards Agency.
Pooling multiple studies in this way means results are less likely to be statistical one offs.
The studies on probiotics and fish oil were all controlled trials where mothers were randomly assigned to a particular diet instead of just reporting what they ate, which also lends credibility to the results.
Looking at 19 studies where mothers took a daily fish oil capsule, they found there was evidence to suggest the daily omega-3 supplement from 20 weeks of pregnancy, and in the first three to four months of breast feeding, decreased the risk of allergies.
These studies tested infants for an egg sensitivity as a proxy for developing other allergies in future.
There was also some evidence to suggest omega-3 could reduce peanut allergies, by as much as 38 per cent. However this was only identified in two studies and therefore not as reliable.
The 30 per cent reduction amounts to around 31 fewer children with an egg allergy for every 1,000 mothers following this regime.
It also looked at 28 trials, covering 6,000 women, taking a variety of probiotic supplements 0 though most of them contained a bacterium called Lactobacillus rhamnosus.
While probiotic yogurt drinks are one source of these sort of gut boosting bacteria, most don’t contain a high enough concentration of helpful bacteria and these studies mostly looked at pill or powder supplements.
The analysis found taking probiotics in the last few weeks of pregnancy and in the first three to six months of breastfeeding, was related with a 22 per cent decrease in eczema cases in children – around 44 fewer cases in every 1,000.
Researchers found some limited evidence to support the suggestion that maternal breast feeding alone helped reduce eczema rates, and could also have benefits for lowering the risk of type one diabetes.
But there was not enough evidence to support other supplements, or leaving out certain foods.
“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,” said Seif Shaheen, professor of respiratory epidemiology at Queen Mary University of London, who was not involved with the study.