Fibre and vitamin A could prevent food allergies

Eating a diet rich in fibre can shape the immune system to reduce allergies to substances such as peanuts, research from Monash University has shown.

The study, published in the journal Cell Reports, also reveals how the immune system works with the good bacteria in the gut to help protect against life-threatening allergic responses, indicating that it may be a lack of fibre in our diets that’s causing the deadly rise in allergies.

By determining how this happens, the researchers have suggested potential treatments to prevent, or possibly even reverse, food allergies. They suggest that allergy treatments could use either probiotics (beneficial bacteria) that recolonise the gut or prebiotics (healthy foodstuffs) that could work together to prevent or reverse allergies.

The research found that mice allergic to peanuts were protected against the allergy when fed a high-fibre diet. In particular, the fibre appears to act by reshaping the gut and colon microbiota.

The study revealed that eating a high-fibre diet actually changes the gut microbiota, the bacteria in the gut, to protect against food allergies. The transfer of these ‘good bacteria’ to mice without these bacteria could reduce the symptoms of food allergies. The microbiota in the gut assist the immune system in resisting allergies through the breaking down of fibre into short-chain fatty acids. This opens up a potential route for drug therapy for allergies by delivering short-chain fatty acids as a treatment.

The scientists found that short-chain fatty acids boosted a particular subset of the immune system called dendritic cells, which control whether an allergic response against a food allergen happens or not. Effectively, increased levels of short-chain fatty acids switch these cells to stop the allergic response, while a lack of fibre may have an opposite effect. These specialised dendritic cells require vitamin A, another factor which can only be obtained through the diet and is high in vegetables and fruits.

While deficiency of vitamin A in adults is unusual, the researchers suggest that less-than-ideal levels of vitamin A, in addition to short-chain fatty acids, could promote food allergies in infants. This may explain why the highest prevalence of allergies occurs in children and infants.

Jian Tan, a PhD student at the Monash Biomedicine Discovery Institute, said the study had not only revealed how the immune system fails when a person becomes allergic, but how the immune system can be helped through diet to prevent or lessen the effects of allergies. He said the next step was to conduct trials with humans to determine how a high-fibre diet can protect against challenges with allergic foodstuffs.