The gut-immune connection How understanding the connection between food and immunity can help us regain our health

"Next to the brain, the gut is the most complex organ in our bodies," gastroenterologist Mayer writes. Take a moment to digest that startling declaration. Nerve cells, immune cells, and endocrine cells work together in the large intestine to control digestion, deliver nutrition, and safeguard against potential intestinal infections. But gut health is intrinsically linked to the trillions of microorganisms that inhabit it. Mayer explains how this remarkable partnership between the microbiome and the gut works. When the population of gut microbes becomes altered by the overuse of antibiotics, our diet, and the increased rate of C-section deliveries, chronic illnesses, including allergic conditions, obesity, and autoimmune disorders, can arise. The diversity of the bacterial inhabitants of the intestine is quite sensitive to diet, and fiber is the major meal for these microbes. Mayer promotes primarily plant-based diets, specifying what foods we should eat, when to eat them, and the importance of how food is produced. He also addresses prebiotics (plant fibers supporting good bacteria), dietary supplements, time-restricted diets, even soil, creating a compelling exploration of our gut's extraordinary ecosystem.

Gastroenterologist Mayer (The Mind-Gut Connection) pursues the connection between chronic disease and the microbiome in this informative if complex work. Rates of "seemingly unrelated chronic illnesses" such as cardiovascular disease, diabetes, and liver disease have been rising over the last 75 years, he writes, but by prioritizing gut health, it's possible to "reverse this trend." To that end, he describes how diet regulates the brain-gut-microbiome network (the gut wall contains more than 70% of the body's immune cells) and reviews the effects of a healthy diet, exercise, and sleep on one's microbiome: disruptions in the brain-body network, he writes, lead to chronic inflammation and increased risk of chronic disease. In the way of advice, he suggests "what to eat" (fiber, green tea, omega-3 fatty acids) and "when to eat" (exclusively in an eight-hour window) to keep the microbiome happy, and dishes out nearly 50 pages of recipes. Lay readers, though, may find the explanations overly scientific ("The production of H2 O2 by Lactobacillus may protect against the development of chronic stress-induced, depressionlike behavior"). The level of granularity is demanding, but readers willing to stay the course will be persuaded to pay more attention to their guts. (June)