There is no substitute for getting a flu shot each year, but if you’ve already contracted the flu, preliminary animal research suggests that a ketogenic diet can help fight the infection once it’s already begun.
Researchers studied the effects of a keto diet by feeding mice a classic keto diet (high fat/low carbohydrate) for a week before they exposed them to the influenza virus. They also kept another control group that ate a low fat/high carbohydrate diet which they also exposed to the flu virus.
The mice that were in the keto group survived the virus better than the mice who did not have a diet modification prior to contracting influenza. The keto group also had lower concentrations of the virus in their body (such as their lungs)—which is quite impressive considering they only ate the keto diet for one week prior to infection.
Scientists believe that the ketogenic diet affects the immune system because it increases the amount of gamma T cells, a type of immune cell that is found in mucus and arms the body against foreign body invaders such as bacteria and viruses. The mice who ate the keto diet had lower amounts of the virus and higher amounts of gamma T cells within the outer layer of their lungs where mucus is prevalent.
To determine what part of the keto diet gave these mice the edge on fighting the flu, scientists gave them a ketone-based drink and a second group was fed the classic keto diet. The drink did not stimulate the immune system at all, and the keto diet increased amounts of gamma T cells. The answer seems to lie in the body making its own ketones and becoming keto-adapted.
This study is definitely food for thought, but it has its limitations. These are results that are promising, but they were conducted with mice. You should also keep in mind that these results are in the early stages, and it shouldn’t dissuade you from getting a flu shot. Remember that getting a flu shot helps protect more than just you and helps keep the infections away from the vulnerable populations, which include the very young and very old—but also includes those people that are healing from surgery, fighting cancer or in remission from cancer, or other diseases which render their immune system more vulnerable.
Goldberg, Emily L., et al. “Ketogenic Diet Activates Protective Γδ T Cell Responses against Influenza Virus Infection.” Science Immunology, vol. 4, no. 41, 15 Nov. 2019, doi:10.1126/sciimmunol.aav2026.