Book review
The Good Gut
The Good Gut by Justin and Erica Sonnenburg was an interesting first look at research into the gut. The authors point out how much remains unknown and how much more research is needed.
These notes were published in 2019 and discuss the book’s microbiome and health claims as presented in the book at that time.
The Good Gut by Justin and Erica Sonnenburg was an interesting first look at research into the gut. The authors point out how much remains unknown and how much more research is needed. They offer some recommendations, including eating more fibre, and reflect on the nutritional choices they have made in their own lives.
What interested me most was the book’s suggestion that we may have more influence over the gut microbiota than over our genes. The authors connect diet, stress and exercise to gut health, while acknowledging that the interaction between the gut, brain and rest of the body is not yet clear. They suggest that the effects can run both ways: stress may affect the gut, and the microbiota may influence how we feel.
Autism is one of their more striking examples. They argue that the microbiota might influence how someone interacts with the world, but the research is still at an early stage. I found their case for further research interesting without seeing it as clear-cut. The book also links the gut to inflammation. In my reading about longevity, I had encountered the idea that background inflammation increases with age, or ‘inflammaging’. We want the body to respond to pathogens, but not to remain constantly active.
The book puts dietary variety and the microbiota together. “Thanks to our typical diet, the average American’s gut bacteria are starving.” The authors say that Americans have about one-third less microbial diversity than people in some indigenous cultures. They give a figure of 100 trillion bacteria in the gut, with some in the stomach and small intestine and most in the large intestine. Their analogy is of a tube running through the body from mouth to anus. One of the book’s other figures is: “Close to half of the mass of stool are bacteria”. They argue that large-scale agriculture and monocrops have narrowed what we eat and affected digestion. The authors also participate in the American Gut Project (research).
Antibiotics are another part of the story. They kill gut bacteria, and the book says that children in the US receive, on average, more than one course per year. Antibiotics save millions of lives, but the authors are concerned about overuse and its effects on the gut. They also discuss how bacteria acquired during a vaginal birth may help establish a baby’s microbiota, and argue that too many babies in the US are born by caesarean section. I recalled the Netherlands as having a relatively low caesarean rate, although I was not certain of that comparison.
The authors describe communication between the gut microbiota and the immune system in both directions. One hypothesis they discuss is that a very hygienic environment gives the immune system less to do, leaving it more prone to reactions to pollen and other allergens. Their description of the relationship is memorable: “The microbiota is like a mercenary in the eyes of the immune system, paid (in slimy mucus) for helping to exclude bad germs but not trustworthy enough to go completely unmonitored.” They add that “The microbiota … also tunes the magnitude and duration of the immune system response”. The book also suggests that owning a pet can help increase microbial diversity.
On food, the authors discuss probiotics but acknowledge that we do not yet know enough to be sure which ones help most. That makes me cautious about supplements; yoghurt, kimchi, tempeh and other fermented foods seem a more appealing place to start. Prebiotics are food-derived components, including polysaccharides and dietary fibre, that feed gut microbes. The book gives inulin and fruit skins as examples.
Sourdough bread is another recommendation I might try. The authors contrast it with white flour and other low-fibre ‘rich man’ foods. They also suggest checking whether yoghurt contains live bacteria. For ageing, the book proposes a diet rich in MACs (fibres or food for the microbiota) and low in saturated fat from animal sources as a possible route to more years of life. That remains a book-era possibility, rather than a conclusion I can establish from these notes.