Can the keto diet help beat the flu?

Results of a new study in mice suggest that the body may be able to defeat the influenza virus if a person has the right sort of diet — a ketogenic, or keto, diet.

Written by Amy Pashler on December 2, 2019 - Fact checked by Gianna D'Emilio

 

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Infection with the influenza virus, better known as the flu, has accounted for 12,000–61,000 deaths every year since 2010 in the United States, with an annual economic burden of $87.1 billion.

The introduction of the flu vaccine has greatly improved infection and morbidity rates. However, there is still currently no cure for the illness.

Healthcare professionals and scientists alike are continuing the search for novel therapeutics to combat the flu, yet the key may lie within the body's own immune system. Moreover, it may be activated by the keto diet.

Following the keto diet involves eating foods that are high in fat and low in carbohydrates. Meals tend to consist of a variety of meat, fish, poultry, and non-starchy vegetables.

According to the findings of a new study, appearing in the journal Science Immunology, when mice fed a keto diet were injected with the flu virus, their survival rates were much higher than those of mice fed a diet high in carbohydrates.

The main reason for this, the researchers believe, is that a keto diet blocks the formation of inflammasomes, which are multiunit protein complexes that the immune system activates.

Inflammasomes can also cause harmful immune system responses in the host. This triggers the release of gamma delta T cells.

Gamma delta T cells are responsible for producing mucus in the linings of the lungs, which helps the body get rid of infectious agents. The mucus is then wafted up the airways and coughed out.

The joint senior authors of the study are Prof. Akiko Iwasaki and Prof. Vishwa Deep Dixit, both of the department of immunobiology at the Yale School of Medicine, in New Haven, CT.

Study design and results

The objective of the study was to determine how the keto diet affects host defense against a lethal flu virus infection.

The researchers randomly assigned the mice to diet groups 1 week before they induced the infection. Next, they monitored the rodents for signs of infection and assessed their immune responses.

The team found that keto diet feeding confers protection against the flu virus in mice by increasing the number of gamma delta T cells in the airways.

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This response occurred relatively late after the infection in the mice, due to their dependence on T cell receptors on other cells. But in humans, this response is much quicker, as gamma delta T cells can expand independently.

In addition, previous research in mice has shown that a specific subset of gamma delta T cells can efficiently induce the cytolytic killing of flu-infected airway cells.

In the current study, the expansion of gamma delta T cells resulted in lower viral titer measurements in the mice that had received a ketogenic diet.

The team also investigated the potential for changes in the levels of genetic activity using RNA sequencing, a technique that can measure the levels of transcription across the genome.

This showed that although a keto diet could impact the expansion of gamma delta T cells, this was not associated with any changes in the activity of genes involved with cytotoxicity.

Interestingly, when mice were bred without the gene that encodes for gamma delta T cells, the keto diet provided no protection against the flu virus.

Commenting on this result, Prof. Iwasaki says, "This was a totally unexpected finding."

"This study shows that the way the body burns fat to produce ketone bodies from the food we eat can fuel the immune system to fight flu infection."

Prof. Vishwa Deep Dixit

How diet may affect the body's defenses

How do gamma delta T cells protect the host in response to a keto diet? As the researchers report, the current theory is that the expansion of these cells — in response to ketogenic feeding — leads to more efficient killing of the flu virus.

This, in turn, results in much lower viral titers and better preservation of the cells lining the airways.

Experts believe that the gamma delta T cells induced by the keto diet may enhance the barrier and innate defense systems of airway-lining cells at baseline, thereby allowing for a better response to the flu virus.

These results demonstrate that the answer to combatting the flu virus does not necessarily lie in producing drugs to relieve flu symptoms — and that changing the diet can have a dramatic effect on how the body responds to infection.

The results also suggest that if the flu can be tackled in this way, there is the potential for changes in diet to help the body more effectively fight other viral infections.

This type of research is in its infancy, and much more will be needed to elucidate exactly how the keto diet may help combat the flu.