The ketogenic diet: its impact on human gut microbiota and potential consequent health outcomes: a systematic literature review.

AIM

This systematic review examined the diet's impact on the human gut microbiota to identify potential consequent health outcomes.

BACKGROUND

The extreme macronutrient profile of the ketogenic diet (KD) instigates compositional shifts in the gut's microbial community.

METHODS

In this systematic literature review, an evidence-based and methodical approach was undertaken, which involved systematic searches of the Medical Literature Analysis and Retrieval System Online (MEDLINE), PubMed and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases, generating a total of 263 relevant research papers. Following the application of inclusion and exclusion criteria, eight papers were deemed suitable for inclusion. These papers were critically appraised using a checklist tool adapted from the National Institute of Care and Excellence (NICE). The findings were analysed using a simplified thematic analysis.

RESULTS

The results provide strong evidence for a persistent reduction in abundance following KD adherence. A reduced abundance of key utyrate-producing bacteria was found to be a likely impact, although two studies with extended intervention periods indicate this may be time-limited. Studies investigating short-chain fatty acids (SCFA's) indicate KD reduces total faecal SCFA's, acetate, and butyrate.

CONCLUSION

Changes to microbial communities resulting from KD adherence are potentially detrimental to colonic health. The persistent reduction in abundance was concerning, with obesity, type-2 diabetes, and depression highlighted as potential consequent risks. For nutrition and healthcare professionals, the findings emphasize the importance of considering KDs microbial effects and resulting health implications at an individual level.