June 23, 2015

expert reaction to dietary fibre in pregnancy and asthma in offspring

A new study performed on mice, published in Nature Communications, has looked at the effect of a mother’s fibre intake on the likelihood of her offspring developing asthma.

Dr Iolo Doull, Royal College of Paediatrics and Child Health, said:

“This is an interesting study that proposes a potential cause for the worldwide increase in asthma. The cause of the increase is not clearly explained, and is likely to be multifactorial, but changes in diet are a possibility.

“The researchers have shown in a mice model that increasing the amount of fibre in the diet changes the gut microflora, and that this has profound effects on the mice developing asthma. They also showed that giving pregnant mice the high fibre diet protected their offspring from developing asthma.  Thus the study proposes a model that could explain how pregnant mothers’ diet could affect the risk of asthma in their children.

“They have a limited amount of data in humans, but that data is sketchy and does not clearly accord with the mice model. In the mice model they induced an allergic response – their model is based on allergic asthma. However the human data is on wheezing in the first year of life, but all human studies suggest that allergy is not a major factor in wheezing in the first year of life.”

Prof. Ian Johnson, nutrition researcher and Emeritus Fellow, Institute of Food Research, said:

“This is an impressive piece of work in which an animal model has been used to show how dietary fibre which is broken down by bacteria in the large intestine can modify the body’s immune system and exert beneficial effects in distant target organs, in this case, the lungs. A particularly interesting aspect of the work is that a change in maternal diet has been shown to induce an epigenetic effect in the offspring, which means that persistent beneficial changes in gene expression have, in effect, been locked into the infant genome without any modification to the DNA sequence.

“The protective effect of dietary fibre against experimental asthma is potentially of great importance, but it must be emphasised that animal models of human disease, though extremely useful for exploring important biological mechanisms, can sometimes show effects that are difficult to reproduce in humans eating realistic mixed diets.  It is encouraging however that the authors have obtained some preliminary data with human mothers which are at least consistent with a protective effect of maternal fibre consumption against asthma in their infant children.  Much more work will be needed to test these results more thoroughly in humans but in the meantime there are many other good reasons to include a variety of fibre-rich foods in our diets.”

Prof. Tim Spector, Professor of Genetic Epidemiology, King’s College London, said:

“This is an important study in showing that in mice dietary fibre and gut microbes in the pregnant mother can determine the risks of the offspring getting asthma.  The lower the fibre content of the mother’s diet– the lower the diversity of the gut microbes. This leads to lower immune suppression chemicals (called short chain fatty acids) – allowing more allergic reactions. The fibre and asthma relationship was confirmed in some human pregnancies.

“Although mice and humans vary in some respects, this study shows the importance for pregnant mothers of having a diverse high fibre diet to nourish the gut microbes which produce key chemicals reducing allergic diseases. The asthma epidemic has now been overtaken by the food allergy epidemic but the message for pregnant mothers should be the same – reverse the trends and eat high fibre and healthy diverse foods to reduce allergies.”

Prof. Barry Kay, Emeritus Professor of Allergy and Clinical Immunology, Imperial College London, said:

“This is an elegant study of the highest quality. But mice, of course, do not get asthma. There are far more differences than similarities in pathophysiology between asthma and murine models. No new treatments for asthma have emerged from experiments on mice. It is called the “mouse trap”.”

‘Evidence that asthma is a developmental origin disease influenced by maternal diet and bacterial metabolites’ by Alison N. Thorburn et al. published in Nature Communications on Tuesday 23 June 2015.

Declared interests

Dr Iolo Doull: Iolo is a Consultant Paediatrician who specialises in respiratory conditions.

Prof Ian Johnson: “Prof Ian Johnson, BSc, PhD is a physiologist and nutrition researcher at the Institute of Food Research in Norwich, where he is an Emeritus Fellow. He is a member of the SACN working group on carbohydrates and health, and a member of the Scientific Advisory Committee of the British Nutrition Foundation. He currently holds no other research funding or consultancies.”

Prof Tim Spector: “Author of book “The Diet Myth” – the real science behind what we eat, W&N 2015”.

Prof Barry Kay declares no conflicts of interest.