That is the name of a fascinating book by Dr. Will Bulsiewicz. He is a well-regarded expert gastroenterologist (“gut doctor”) both as a practitioner and clinical researcher. The main thesis of the book is that our gut microbiome, or the trillions of bacteria in our small and large intestines, play a major role in nutrition and health. He gives strong evidence that a lot of individual differences in digestion and food sensitivities are less attributable to genetics, and more to the status of these bacteria. And this status is largely affected by what we eat. The good news is that it doesn’t matter what our current status is, it is highly changeable by fixing our nutrition.
Too often it is assumed that if we have certain food sensitivities, we simply have to avoid those foods for life. The most common misconception is that this is true for prediabetes and diabetes and carbs- “your body doesn’t handle carbs well, you have to keep your carbs low”, in an oversimplification. In truth, your body is insulin resistant, but insulin resistance can be lowered through diet, including eating a lot of good carbs. The same can be true for non-celiac gluten sensitivity and fodmap sensitivity, according to Dr. Bulsiewicz. Fixing our diets can change gut bacteria and clean up these conditions as well.
But this has to be done gradually. His motto is “start low and go slow”: if you are sensitive to a certain food, you can gradually reintroduce it, and your gut bacteria will reconfigure themselves, until eventually you tolerate it. He has a four week program to take you through doing just that. Again, for certain severe conditions like celiac disease this will not work, and for more serious intolerances you should work with a professional while making changes like this. But many of us with milder sensitivities do not have to accept them as “life sentences” of abstention from the foods in question.
Dr. Bulsiewicz is a strong believer in the whole-food plant-based diet, because he feels there is a lot of data showing animal products adversely affect the gut microbiome. He urges aiming for a diet of no more than 10% animal products (preferably no dairy), with the remainder high-quality plant whole plant foods.
I highly recommend the book for detailed information from an expert in this field.