A recent study reports that dietary fiber consumption reduces influenza virus infection by decreasing respiratory tissue inflammation and increasing antiviral immune response.
The flu or influenza virus responsible for influenza has a very high contagion potential and infects 5 to 15% of the world’s population each year. The most common clinical symptoms of infection are runny nose, sore throat, fever and general malaise, but this response to the virus can vary greatly from person to person. Some are downright devastated by the virus and remain bedridden for a few days, while others are much more tolerant and show only mild symptoms of infection.
It seems that these differences in sensitivity are due to the inflammation generated in response to the virus: in sick people, it is the genes involved in the production of inflammatory and stress-response molecules that are predominantly activated, while in resistant people, it is rather genes that trigger an anti-inflammatory and antioxidant response that are activated. Identification
of the factors responsible for these different responses could therefore prove to be very interesting in minimizing the negative impacts of influenza on health.
Food: a major lever to strengthen your immunity
One of the most important known modulators of inflammation is diet, in particular the dietary fiber present in high amounts in most plants. The gut microbiome (the hundreds of billions of bacteria that colonize our gut) feeds on these fibers through fermentation, which generates several short-chain fatty acids like acetate, propionate and butyrate that act on cells of the immune system and reduce inflammation. Several studies suggest that this anti-inflammatory activity of short-chain fatty acids could play a very important role in preventing the immune system from racing and triggering a disproportionate response that damages tissues or promotes the development of autoimmune diseases. (allergies, type 1 diabetes, lupus).
Artichokes, garlic, asparagus, bananas: foods rich in inulin
A recent study suggests that the anti-inflammatory action of short-chain fatty acids may also play an important role in the antiviral response to influenza virus. A team of Australian researchers has shown that animals that ate a diet rich in inulin (a soluble fiber abundant in certain plants such as artichokes, garlic, asparagus and bananas) were much more resistant to infection by the virus of influenza and had less lung damage caused by the virus than those who consumed low fiber. A detailed analysis showed that this protection was due to two major phenomena:
– 1) A reduction in the infiltration of white blood cells (neutrophils) in the respiratory tract, which attenuates the destruction of lung tissue caused by these immune cells.
– 2) An increase in the activity of CD8 lymphocytes, killer cells specialized in the elimination of viruses.
In other words, a diet rich in fiber optimizes the response to the virus by increasing antiviral immunity on the one hand and, on the other hand, by reducing excess inflammation that can damage the lungs. These positive effects are correlated with a significant change in the composition of the microbiome of the models: inulin supplementation causes an increase in bacteria of the Bifidobacterium type and a very significant increase in the levels of short-chain fatty acids, in particular butyrate. Interestingly, the mere fact of adding butyrate to the water consumed by the models is sufficient to reproduce the anti-influenza protection offered by the high-fiber diet, confirming that it is really the production of fatty acids at short chains by the gut microbiome which is responsible for changes in immune function.
Prepare for the arrival of the flu by increasing the consumption of plants
The prevention of influenza could therefore be added to the many already known effects of dietary fiber for the prevention of cardiovascular diseases and certain types of cancer (the colon, in particular). Currently, the European diet is very low in fiber (10-15 g per day instead of the recommended 30-40 g) and the best way to remedy this situation is to increase the total consumption of vegetables, for example legumes , cereals (especially whole grains), nuts, fruits and vegetables.
Huang Y et al. Temporal dynamics of host molecular responses differentiate symptomatic and asymptomatic influenza A infection. PLoSGenet.2011;7:e1002234.
Trumpet A et al. Dietary fiber confers protection against flu by shaping Ly6c-patrolling monocyte hematopoiesis and CD8+ T cell metabolism. Immunity 2018; 48: 992-1005.