Brain Maker

Brain Maker argues that the health of the brain is shaped substantially by the bacteria in the gut, and that many neurological and psychiatric problems should be approached as downstream consequences of a disturbed microbiome. David Perlmutter's claim is that the gut-brain relationship has been underappreciated in conventional neurology, and that dietary and microbial interventions deserve a central place in brain health.

The proposed mechanism combines several strands: gut bacteria influence systemic inflammation, produce and modulate neurotransmitters and short-chain fatty acids, interact with the vagus nerve, and affect the permeability of both the intestinal wall and the blood-brain barrier. Perlmutter argues that modern diets high in refined carbohydrate and sugar, along with antibiotic exposure, caesarean delivery and formula feeding, disrupt this system. His recommendations centre on a low-sugar, low-carbohydrate, gluten-free diet rich in fermented foods, prebiotic fibre and healthy fats, with probiotic supplementation and, in his more speculative chapters, faecal microbiota transplantation.

The audience is general readers interested in the gut-brain connection, and it is written clearly enough for someone with no background in neurology.

On the evidence, the gut-brain axis is a legitimate and rapidly moving field, and the general direction — that the microbiome interacts with the nervous system — is supported. The difficulty is the distance between that broad finding and the book's specific claims. Much of the strongest microbiome-behaviour data comes from animal models, where results have often not translated to humans. Perlmutter's assertions linking the microbiome to autism, depression, multiple sclerosis and Alzheimer's disease go considerably further than the human trial evidence allows, and his position on gluten for people without celiac disease or diagnosed sensitivity is contested within gastroenterology. The dietary advice is unlikely to cause harm, but the book should not shape decisions about diagnosed neurological or psychiatric conditions.