Book review: The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-term Health, by Justin Sonnenburg and Erica Sonnenburg.
I had hoped this book would help me improve my gut health. Alas, their advice is of limited value, mostly focusing on changes that I’d already adopted based on other types of nutritional ideas, such as eating more fiber from diverse sources. That limited value is probably due mostly to the shortage of useful research on this subject, rather than to any failing of the authors. Research on these topics seems hard due to the complexity of the microbiome, and the large variation between people.
The book convinced me to eat more kimchi, and left me wondering whether to try consuming more bacteria in pill form.
The book repeats warnings that I’d read elsewhere about the dangers of antibiotics, and the problems that arise from having an insufficiently diverse microbiome, such as autoimmune diseases.
I have been placing heavy emphasis on fiber in my nutritional strategies, while having a gut feeling that the concept of fiber left something to be desired. The book pointed me to an alternative concept: microbiota accessible carbohydrates (MACs), which mostly means carbs that aren’t absorbed by the small intestine. A diverse set of MACs feeds a diverse set of microbiota, which at least correlates with good health.
Alas, it seems impossible to reliably measure MACs by analyzing food in isolation – different people’s small intestines absorb different substances. There are also complications such as erythritol, which is mostly absorbed in the small intestine (and is then removed without doing much), but about 10% of which ends up feeding microbiota in the colon. So I’m still stuck with estimating my MAC consumption via the standard fiber estimates, and taking care to get it from diverse sources.
The Sonnenburgs explain that food preparation affects absorption. Flour is absorbed faster than less-processed grain, and the meaning of “flour” has changed over the past century or so, from something that was ground coarsely and eaten soon after, to something that is ground very fine, and stays on a shelf long enough to go rancid if it is whole-grain flour. That nudged me toward a more nuanced position on grains. The “grains are not food” rule was a simple way to improve my diet, but there are clearly big differences between the best whole grains and the worst grain-derived products.
It also helps me understand how grains, as typically used, gradually morphed into mostly being junk food without an easy way to detect the worst effects. More sophisticated machines to grind the grains led to a texture that was more quickly absorbed, leaving less for microbiota. The switch away from whole grain flour was likely, in part, a gradual adaptation to a system where the flour was ground at an increasingly distance from the home, and became more likely to go rancid if the germ wasn’t discarded.
The book has a section on how infants get a microbiome, which explains why it’s really hard to find or create a good substitute for human milk.
The Sonnenburgs have unusual heuristics about when they wash their hands, designed to reduce pathogens while welcoming good bacteria. They avoid washing after gardening or petting the family dog, but are careful to wash after going to places where they could get germs from many other people – malls, petting zoos, etc.
I’m discouraged by the news that microbiome treatments such as Fecal Microbiota Transplantation (FMT) may be regulated as drugs. It seems like regulations should be modeled somewhat more closely on food, or blood transfusion, regulation. Like food, FMT should have broader goals than just combating specific diseases, should provide diverse inputs, and should bear some resemblance to what naturally enters our bodies. Like blood transfusions, FMT should be reasonably safe unless there’s something unusual about the donor.
The book’s advice overlaps a lot with paleo-like advice to go back to how our ancestors ate, played, etc., with a rather balanced approach to borrowing from our grandparents’ lifestyle versus borrowing from hunter-gatherer lifestyles. The book is solid, often at the expense of being exciting.