January 28, 2021

expert reaction to study looking at omega-3 fatty acids and asthma in children

A study published in the European Respiratory Journal looks at asthma in children and omega-3 dietary intake.

Dr Prasad Nagakumar, Paediatric Respiratory Consultant, Lead for Severe Asthma, Birmingham Women’s and Children’s Hospital NHS Trust, and Honorary Senior Lecturer in the Birmingham Clinic Trials Unit, University of Birmingham, said:

“In a study published in ERJ, Talaei and colleagues using data from two large birth cohorts have shown that in children aged 7 years with a specific variant in FADS gene, high dietary intake of long chain omega 3- fatty acids is associated with 51% reduction in risk of developing asthma at age 11-14.  The study population included predominantly Caucasian subjects, mostly not from lower socioeconomic status.  Few studies in the past have shown reduction in risk of offspring developing asthma when such dietary modifications are made in pregnant women or in infants.  This well-designed study provides valuable data showing that dietary modifications in certain primary school children may prevent development of asthma in them at secondary school age.

“However, this observational association should be interpreted with caution.  Asthma is a heterogeneous disease with age, ethnicity, genes, nutrition, and environment impacting on the development of the disease.  Modifying one factor may not be enough to prevent the development of asthma.  Based on this study, we cannot conclude that a diet rich in omega 3 fatty acid prevents development of asthma.  However, we know from previous research that eating more fish will certainly have a positive impact on young children’s well being in other ways.”

Dr Duane Mellor, Registered Dietitian and Senior Teaching Fellow, Aston Medical School, Aston University, said:

“This is a well designed study following over four and a half thousand children from the age of 7 to the age of 11-14 in the Southwest of England.  The research team looked to see if the intake of certain types of fats (fatty acids known as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid)) which are most commonly found in fish were linked to the risk of a child developing asthma.

“Overall, this study did not find a link between children eating this type of fat from fish and the risk of developing asthma.  However, the ability to make these complex and vital fats which are useful in maintaining the health of our cell membranes as well as being associated with lower levels of inflammation may depend on the type of genes we have.  In the case of these long polyunsaturated fats if we cannot get them from our diet, we need an enzyme called fatty acid desaturase, this helps to remove hydrogen from more saturated fatty acids to make them less straight and therefore less solid, helping to make our cell membranes more flexible and healthy.  Some people tend to have carry a gene which makes a less effective fatty acid desaturase, so limiting the ability to make the types of fatty acids found in fish.  Only children who had the gene which could limit their ability to make the longer unsaturated fatty acids were more likely to have asthma if their intake of EPA and DHA from fish was lower.

“The link between this gene variant and fatty acid intake from fish was also seen in a population of children in Sweden.  This along with other studies which have observed a link between the gene, levels of fats in the blood and asthma led the researchers to conclude that their appears to be an association between risk of developing asthma and intake of certain fats which are found in fish in children with a certain gene variant.

“This is an interesting finding, however although there are a number of apparent associations between the gene, dietary intake of fats from fish and risk of developing asthma, there is no definite causality, although statistics suggest this could be possible.  The research focused on intake of fats from eating fish, it did not look at fish oil supplements, so this research does not provide evidence to suggest fish oil supplements can reduce a child’s risk of developing asthma.”

Dr Alister McNeish, Associate Professor in Cardiovascular Pharmacology, University of Reading, said:

“This interesting data indicates that higher rates of early childhood of fish consumption and thus omega-3 fatty acid consumption appears to be associated with a lower rate of asthma; but only in children who have a common gene make up that is associated with lower levels of omega-3 in the blood (FADS genotype).

“In the cohort as a whole and children who do not carry this gene-make up the link between fish consumption and asthma does not occur, which is consistent with previous cohort studies where no link was found between fish consumption and asthma.

“A key strength to this conclusion is the large numbers of people studied and data from an independent cohort from Sweden analysed in this study reached the same conclusions meaning it was less likely to be a chance observation.  Combined with the size the cohort it suggests the link is not a chance observation.

“Confounding factors associated with high intake of fish were also investigated with no links  found, making the conclusion that it was omega-3 fatty acid intake that was the key factor related to higher fish intake.

“It is worth noting that food surveys were used to estimate  intake – actual levels of fish consumption or levels of omega-3 fatty acids in the blood were not known in the UK study.  However blood levels of omega-3 were known in the Swedish cohort adding further credence that idea that omega-3 intake is key.

“The authors correctly state that they have an observational association not definitive proof that eating more fish in childhood protects from asthma.  The conclusions are fair and acknowledge the key limitations in the work.

“These findings do not constitute proof that eating more fish in childhood prevents asthma.  However levels of omega-3 consumption in the UK are often below recommended levels.  The observations are consistent with other areas of omega-3 research such as in the cardiovascular system where a beneficial effect is often only seen in people with low intake or  low blood levels omega-3s.”

Dr David Richardson, Founder and Director of DR NUTRITION (a company that provides specialist consultancy on food science and nutrition), said:

“This is one of the few well designed and executed studies which investigate the associations between intakes of fish and the long chain omega 3 fatty acids EPA and DHA on asthma and allergic diseases.  The study highlights how genetic make up and predisposition can significantly affect incidence of asthma in children.  Several confounding factors can make the interpretation of the study and recommendations for dietary intakes difficult, but the authors do shed light on the complicated area of gene-nutrient interactions.  As the authors suggest a strategy of personalised primary prevention may help this large subgroup of the population.  However, the actual proportion of the population with this particular genotype was not actually stated in the abstract or conclusions.

“This research should be interpreted in the general context of the results of the UK National Diet and Nutrition Survey (NDNS) published by Public Health England in December 2020¹.  Whereas Government advice is to consume at least two portions (140 g) of fish per week, one of which should be an oily fish (e.g. salmon, herring, sardines and mackerel), which are high in EPA + DHA, the mean consumption of oily fish was equivalent to 56 g per week in adults aged 19–64 years and mean consumption in children was less than 20 g per week.  Much more should be done in the Government’s public health messages to highlight this area of nutritional concern.”

1 Public Health England.  The National Diet and Nutrition Survey (NDNS).  Report of Years 9 to 11 (2016 to 2017 and 2018 to 2019 of the Rolling Programme).  Published December 2020.

‘Intake of n-3 polyunsaturated fatty acids in childhood, FADS genotype, and incident asthma’ by Mohammad Talaei et al. was published in the European Respiratory Journal at 00:01 UK time on Thursday 28 January 2021.

DOI: 10.1183/13993003.03633-2020

Declared interests

Dr Prasad Nagakumar: “No conflicts of interest.”

Dr Duane Mellor: “I have no declarations of interests.”

Dr Alister McNeish: “I am a researcher into the cardiovascular effects of n-3 PUFAs and currently hold 2 research grants from the British Heart Foundation  to investigate the effects of these fatty acids on normal vascular physiology.”

Dr David Richardson: “I am a scientific consultant to the Council for Responsible Nutrition UK. I run my own consultancy in nutrition and food science called DR Nutrition.”