The ketogenic diet may help fight against the flu

Researchers found that the popular diet could confer some benefits to your immune system.

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  • The ketogenic diet works by tricking your body into thinking its in starvation mode — with very few carbohydrates to turn into glucose, your body instead burns fat to use as energy.
  • While most go on the diet to lose weight, evidence suggests a whole host of additional benefits to mental and physical health, though these findings still need to be confirmed.
  • Recent research has added another potential benefit to the keto diet: It could help you defend against flu infections.


The low-carb, high-fat ketogenic diet might not just be good for your waistline; it could also keep you healthy this flu season. Yale University researchers discovered that mice who were fed a ketogenic diet were better at fighting off flu infections that those fed a high-carb diet instead.

How does the keto diet work?

People can use the keto diet to quickly lose weight by capitalizing on a metabolic state called ketosis. Normally, the human body gets most of its energy from glucose (i.e., blood sugar) derived from carbohydrates, but the body doesn't have a good way of storing glucose. Because of this, the humans need an alternative energy source to get them through periods when they can't get access to any food. Once the body is deprived of glucose, the liver begins to break down fat into an alternative energy source called ketones that can keep the body going long after it last ate.

Luckily, we can jump into this metabolic state without having to actually starve ourselves by simply eating no or very little carbohydrates — eating more fats and proteins keeps us feeling full while our bodies still burn fat to make ketones.

Interestingly, the keto diet seems to have a lot more effects other than weight loss. Ketosis appears to have wide-ranging effects throughout the body, with potential beneficial outcomes for diabetics and epileptics. There's also some evidence suggesting a correlation between the keto diet and improved mental health and better outcomes in cancer treatments — though the research is still far from conclusive.

Now, it appears that the keto diet could offer another benefit: an improved defense against the flu. Researchers administered a lethal dose of the influenza A virus to two groups of mice: one group that was fed a keto diet and another that was fed a more standard diet. The keto mice consistently survived and fared better overall.

A thinner waistline and a stronger immune system

The researchers discovered that a keto diet appeared to activate genes that produce a specialized type of immune cells called gamma delta T cells. Tissue samples from the lungs of mice in the keto group confirmed that they had higher levels of these cells. The researchers suspected that these elevated levels of gamma delta T cells killed infected cells in the mice's lungs, and they also appeared to increase mucus production in the lungs, helping to trap more of the virus.

Furthermore, when the researchers fed a keto diet to mice specially bred to lack the genes that code for gamma delta T cells, the diet had no effect on their survivability, confirming that ketosis was somehow upregulating these genes.

Further experiments confirmed that ketosis itself, rather than just a low-carb diet, seemed to be the triggering factor. The researchers fed some mice a high-fat diet with less carbs than the standard diet but more than the keto one. Specifically, the keto diet contained less than 1 percent carbs, the standard diet contained 58 percent carbs, and the high-fat, high-carb diet contained 20 percent carbs. While the high-fat, high-carb diet did elevate gamma delta T cell levels, it did not appear to do so to the degree where any benefit could be gained.

Remember to take your bacon-avocado omelet with a grain of salt

While this exciting finding does suggest that the keto diet may help you power through flu season, it's important to remain realistic. For one, this study was conducted on mice, not humans. Animals respond differently to both treatments and diseases than humans do, and some researchers have found that animal trials tend to be conducted under different circumstances than human trials and can be less rigorous as well, sometimes resulting in biased findings.

What's more, the keto diet may come with many health benefits, but its also not without its risks. The high meat component of the keto diet can damage your kidneys and cause gout, and the diet's restrictive nature can lead to vitamin deficiencies. It ought not need to be said, but pregnant women and young children shouldn't be put on the keto diet — the diet tricks your body into thinking it's starving, which is not ideal for development.

Ironically, quickly switching from your normal diet to a keto one can actually give you flu-like symptoms. The "keto flu" is a temporary side effect of rapidly removing carbs from your diet that can cause nausea, headaches, weakness, issues with concentration, and other symptoms. Hardly ideal if you're trying to stay ahead of the flu bug!

Fortunately, most of these negative effects can be mitigated or avoided by building a healthy keto meal plan and transitioning gradually into a keto diet. Undertaking any diet with the goal of improving your health will require doing some homework to figure out what works, and the keto diet is no exception. It's also important to remember that the keto diet probably works best as a short-term diet. Few people can stick with the diet over the long term, so hard evidence on its long-term impacts is scant, but it's unlikely that excluding healthy components of a normal diet (like fruit) would be sustainable. That being said, if these findings are verified, then it might not be a bad idea to try the keto diet once flu season rears its ugly head once again.

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