Study: Vegan, Keto Diets Impact Immune System, Gut Health

A recent study by the National Institutes of Health (NIH) in the US has found that switching to vegan or ketogenic (keto) diets can cause rapid and distinct changes in the immune system and the gut microbiome. The study, published in the journal Nature Medicine, compared the effects of two weeks of vegan and keto diets in 20 healthy volunteers.

Vegan Diet and Innate Immunity

The vegan diet, which consisted of 10% fat and 75% carbohydrates, was found to trigger responses associated with innate immunity, or the immune system that one is born with. Innate immunity is the body’s non-specific first line of defense against pathogens, such as viruses and bacteria. The researchers observed that the vegan diet affected more pathways and cell enrichment related to red blood cell production, likely due to the iron-rich content of the diet. The vegan diet also promoted antiviral responses and pathways involved in inflammation and wound healing.

Keto Diet and Adaptive Immunity

The keto diet, which consisted of 76% fat and 10% carbohydrates, was found to trigger responses associated with adaptive immunity, or the immune system that one develops with time in response to external infections and vaccinations. Adaptive immunity is the body’s specific and long-lasting defense against pathogens, mediated by antibodies and T cells. The researchers observed that the keto diet affected more pathways and cell enrichment related to plasma, brain and bone marrow. The keto diet also enhanced antibody responses and pathways involved in cellular stress and DNA repair.

Gut Microbiome Changes

Both diets also caused significant changes in the participants’ gut microbiomes, or the communities of bacteria living in the digestive tract. The gut microbiome plays an important role in metabolism, immunity and overall health. The researchers found that the vegan diet increased the diversity and abundance of beneficial bacteria, such as Bifidobacterium and Lactobacillus, which are known to produce short-chain fatty acids that have anti-inflammatory effects. The keto diet decreased the diversity and abundance of beneficial bacteria, but increased the abundance of bacteria that can produce hydrogen sulfide, a gas that has been linked to intestinal inflammation and colorectal cancer.

Implications and Limitations

The study results showed that the immune system responded surprisingly rapidly to nutritional interventions, suggesting that it may be possible to tailor diets for patients to prevent disease or complement disease treatments, such as by slowing processes associated with cancer or neurodegenerative disorders. However, more research is needed to determine if these changes are beneficial or detrimental and what effect they could have on long-term health outcomes. The study was also limited by its small sample size, short duration and lack of control group.