The Care and Feeding of Gut Bacteria

The Diet Myth: The Real Science Behind What We Eat

by Tim Spector

Weidenfeld and Nicholson (2015)

Book Review

The Diet Myth is all about looking after our intestinal bacteria – which are ultimately responsible for the proper functioning of our digestive, immune, endocrine and nervous system. As Professor Tim Spector explains, all mammals co-evolved over millions of years with the bacteria that inhabit their intestines. Because these bacteria produce a number of vital biochemicals that our bodies are genetically incapable of producing, without them the species homo sapiens would not exist. This relatively recent discovery has led many scientists to classify the microbiome (the collective name given to gut bacteria) as a vital organ like the brain, liver or kidneys.

Civilization hasn’t been kind to our intestinal bacteria. For various reasons (overuse of antibiotics, processed foods and pesticides like Roundup), urban life has caused us to lose half of the septillions of gut bacteria we started out with. Nearly all the chronic illnesses that plague modern society (obesity, heart disease, stroke, diabetes, cancer, autoimmune disease, depression, autism, schizophrenia and possibly drug addiction and alcoholism) can be traced to loss or malfunction of intestinal bacteria.

For this book, Spector has chosen to focus on dietary research into foods that improve the health and diversity of our remaining gut bacteria. He blames the myriad of contradictory diet fads on the reality that each human being has their own distinct collection of bacteria. This means the foods that keep them healthy depend on the preferences of their particular bacteria.

Fortunately he’s able to make a few general recommendations that seem to apply to most people.

According to Spector, people with the most diverse profile of gut bacteria are the healthiest. The best way to promote this diversity is through a diverse fiber-rich diet that includes:

• At least 20 different food types per week
• A daily serving of 5 vegetables and 2 fruits
• Daily servings of probiotic foods (fermented foods, such as yogurt, sauerkraut and miso, raw milk and unpasteurized cheeses) that contain beneficial bacteria.*
• Daily servings of prebiotic foods rich in polyphenols that gut bacteria love**
• A strict limitation on red meat,*** sugar, refined carbohydrates, transfats (hydrogenated fats found in vegetable oils, margarine and Crisco) and processed foods

Research also indicates that lifestyle factors such as exercise (athletes have the most diverse microbiomes) also promote bacterial diversity (and good health). As does episodic fasting.****

---

*These mainly provide different strains of lactobacillus and bifidobacteria that crowd out harmful inflammatory gut bacteria.

**Foods rich in polyphenols include dark chocolate, coffee, green tea, turmeric, red wine, onions, garlic, (uncooked) extra-virgin olive oil, roasted nuts, Jerusalem artichokes, chicory root, leeks, asparagus, broccoli, bananas, wheat bran and fermented fruits and vegetables.

***Citing numerous studies, Spector totally debunks the claim that red meat is harmful due to its fat content. He maintains the risk associated with red meat is the conversion (by gut microbes) of L-carnitine to trimethylamine oxide, which causes plaque build-up in arteries (in Europeans – this effect appears to be absent in other ethnic groups). He recommends that Europeans limit their intake of red meat to ½ serving or less per day. Those who eat more than this have a 10% increase in mortality. Those who eat one daily serving or more of processed meat (sausages, ham, salami, etc) have a 40% increase in mortality.

****When people fast, a gut organism caused Akkermansia cleans up gut inflammation by feeding off the intestinal lining. Research reveals specific benefit from the 5/2 diet in which people fast two days a week and eat normally the other five.