A Western dietary pattern, characterized by a low intake of fruits and vegetables and a high intake of red and processed meats and added sugars, promotes chronic diseases, including obesity. It also increases low-grade inflammation by directly reprogramming immune cells to become pro-inflammatory. Authors of a recent report investigated the impact of a ketogenic diet on immunity.
Glucose is the primary energy source for most cells in the body. However, when a person fasts or restricts carbohydrate intake, the body produces ketones from dietary and body fat for energy. One such ketone is beta-hydroxybutyrate, which has been shown to ameliorate low-grade inflammation and related diseases in mice. Whether consuming a very low carbohydrate diet alters immunity in humans is unclear.
The investigators recruited 44 healthy adults to complete a three-week ketogenic diet that provided less than 30 grams of carbohydrates per day (the amount in about two slices of sandwich bread). Participants gave blood samples before and after the diet period for measurement of immune cells, including antibody-producing T cells. The researchers exposed white blood cells from the pre-diet and post-diet timepoints to varying concentrations of beta-hydroxybutyrate for 48 hours, stimulated them to produce an immune response, and measured the effect.
When exposed to beta-hydroxybutyrate, pre-diet white blood cells associated with the innate immune system (the driver of chronic low-grade inflammation) did not alter their behavior; however, antibody-producing white blood cells associated with the adaptive immune system became more active. CD4+ and CD8+ T cells exposed to the highest concentration of beta-hydroxybutyrate (10 millimolar), comparable to the maximum circulating level in humans, produced more cytokines used to fight infection. Regulatory T cells, which prevent autoimmunity and excessive inflammation, also increased their activity, including the mitochondrial metabolism of ketones. Participants lost a significant amount of weight over the three-week ketogenic diet period, and their post-diet T cells showed the same metabolic and immunological responses as those in the in vitro experiment.
The authors concluded that a very low carbohydrate diet or ketogenic diet is a clinical tool for improving T cell-mediated immunity. They suggested that nutrition and dietary interventions should be used more in modern medicine.
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