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NIH Record - National Institutes of Health

Switching to Vegan or ‘Keto’ Diets Rapidly Affects Immune System

NIH researchers observed rapid and distinct immune system changes in a small study of people who switched to a vegan or a ketogenic (keto) diet. 

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Scientists closely monitored various biological responses of people sequentially eating vegan and keto diets for two weeks, in random order. They found the vegan diet prompted responses linked to innate immunity—the body’s non-specific first line of defense against pathogens—while the keto diet prompted responses associated with adaptive immunity—pathogen-specific immunity built through exposures in daily life and vaccination. Metabolic changes and shifts in the participants’ microbiomes—communities of bacteria living in the gut—were also observed. 

More research is needed to determine if these changes are beneficial or detrimental and what effect they could have on nutritional interventions for diseases such as cancer or inflammatory conditions.

The keto diet is a low-carbohydrate diet that is generally high in fat. The vegan diet eliminates animal products and is high in fiber and low in fat.  

The study was conducted by researchers from NIAID and NIDDK’s metabolic clinical research unit in the Clinical Center. The 20 participants were diverse with respect to ethnicity, race, gender, body mass index and age. 

Each person ate as much as desired of one diet (vegan or keto) for two weeks, followed by as much as desired of the other diet for two weeks. Throughout the study period, blood, urine and stool were collected for analysis. Participants remained on site for the entire month-long study, allowing for careful control of the dietary interventions. Switching exclusively to the study diets caused notable immune system and metabolic changes in all participants. 

The results of this study demonstrate that the immune system responds surprisingly rapidly to nutritional interventions, suggesting it may be possible to tailor diets to prevent disease or complement disease treatments.

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