Microbes make the meal, new diet book proposes

The Diet Myth
Tim Spector
Overlook Press, $28.95

For 10 days, Tom Spector lived off McDonald’s. He had chicken nuggets or Big Macs for meals and McFlurries for dessert. Tom, a 22-year-old student, was re-creating a version of the diet made famous in the film Supersize Me. But Tom’s plan had a twist: Before and after the diet, he gave his dad some poop.

Tom’s father, Tim, wanted to see how the bacteria in Tom’s intestines dealt with junk food. Tim Spector, a genetic epidemiologist at Kings College London, thinks that the billions of bacteria in our guts may help explain health problems including obesity and allergies.

In The Diet Myth, Spector makes a convincing case. His son’s McDonald’s diet whittled down microbial diversity, which has been linked to health. The diet also swapped out friendly, diarrhea-preventing bacteria for ones that trigger inflammation. Spector backs this personal story with a mountain of evidence and cuts through diet myths like butter.

Dairy products, for instance, have gotten a bad rap. High-fat milk, yogurt and cheese actually seem to be good for you, Spector argues. But stick to cheddar, Gouda and other aged cheeses, he advises, or blue-veined varieties such as Roquefort. These cheeses are microbe metropolises and may keep people healthy, studies in humans have shown.

From Atkins to The China Study to a French fad calledle forking (followers eat only with a fork), Spector dumps decades of diet trends into a sieve to see what shakes out.

There’s not a whole lot there, he finds. Spector skewers popular heath crazes: Multivitamins? Worthless. Superfoods? A marketing con. The Paleo diet? Majorly flawed.

And a diet that works for one person won’t necessarily work for a neighbor — or even a twin. Spector would know. He’s the architect of the U.K. twins registry, a collection of data from 12,000 twins. He draws on twins’ stories to dispel the myth that peoples’ bodies deal with food in the same way. “They don’t,” he writes. “We are all different.”

One huge factor influencing individuals’ health and weight, he argues, is our microbes. Like Michael Pollan’s 2009 bestseller In Defense of Food, The Diet Myth challenges widely held ideas about food and eating. Spector even riffs on Pollan’s famous advice to eat what your ancestors ate: “Don’t eat anything your great-grandmother’s microbes wouldn’t recognize as food.”

To take care of your body, Spector suggests, take care of your microbes. That means mixing up your diet, he says.

Variety is key. Try to avoid antibiotics. And one thing most diet books can agree on: Lay off the McDonald’s.

Buy The Diet Myth from Amazon.com. Sales generated through the links to Amazon.com contribute to Society for Science & the Public’s programs.

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Editor’s note: Due to a production error, a preliminary draft of this review was posted online on September 2. The text was updated on September 3, 2015.