It happens with some regularity. A young, fit guy will overdo the weekend routine and come to Manhattan alternative doctor Frank Lipman for a course of acupuncture to relieve the ache of a sore back or a strained shoulder. He'll have his problem muscles addressed, but he won't leave Lipman's office without also hearing the doctor's case for a full dietary plan that emphasizes loads of fresh vegetables and fruits, and eliminates added sugars, gluten, and dairy. "Then they'll write me an email that says something like, 'Damn, I didn't know I could feel like this!'" says Lipman.
These are not unhealthy patients, and they didn't complain of low energy before their visit. So why should these dietary fixes have such a dramatic effect?
The answer has emerged in a frenzy of scientific activity that, in the past five years, has transformed the way we look at the human body and our health. The object of all this attention is the microbiome, the collective of microbes that live within us, mostly in the gut. These bugs are primarily bacteria, but there's also yeast, fungus, and parasites. Ever since the 17th century, when Antonie van Leeuwenhoek scraped a bit of crud from between his teeth and put it under an early microscope, science has known that we are home to single-celled creatures invisible to the naked eye. But not until the recent advent of genomic sequencing that can read the DNA of our cells did biologists appreciate just how many of them there were within us: For every one human cell in our body, there are 10 microbial cells.
"The idea that we're more microbe than mammal is as or more profound than the theory of evolution," says anthropologist Jeff Leach, one of the founders of the American Gut Project, devoted to genetically mapping the microbiome. Biologists see humans' digestive system as a wet home and steady food supply for trillions of bacteria. In return, the bacteria break down and thrive on the plant fiber that we eat but otherwise cannot digest, and join forces with our immune system cells to fight pathogenic invaders – harmful bacteria like salmonella and E. coli that lurk in spoiled food and in the soil.
The microbiome gives Lipman a new way to express the dietary advice he's been dispensing to patients for years: Eating more vegetables, steering clear of processed foods, and diversifying one's diet happen to be the best ways to promote healthy bacteria in the body. And a thriving microbiome is essential to overall health.