What is a ‘healthy’ microbiome?

| November 3, 2014

The microbiome is one of the hottest current topics in biology. According to various studies, our gut microbial community may partly account for obesity, diabetes, and the state of our immune system. Fascinatingly, nobody harbors exactly the same microbiome as anyone else: they are as unique as our diets, lifestyles, and where in the world we live.

But some of the hype around gut microbiomes is dubious. In a New York Times opinion piece, science writer Ed Yong – who frequently reports on the microbiome for National Geographic – lamented the tendency to over-exaggerate the power of gut microbes. He pointed to problematic exploitation of non-conclusive science by the probiotics and diet industries, as well as a self-experiment by Jeff Leach to replace his own gut microbes with those of a Hazda tribesman from Tanzania.

“This reasoning is faulty. It romanticizes our relationships with our microbes, painting them as happy partnerships that were better off in the good old days. It also invokes an increasingly common trope: that there is a ‘normal’ or ‘healthy’ microbiome that one should aim for. There is not. The microbiome is complex, varied, ever changing and context-dependent — qualities that are the enemies of easy categorization.”

The trouble with categorizing the microbiome, according to Yong, is that each one is too different form the next. A certain feature may exist within one population that is completely absent from another. This does not mean one is better: they are simply different. Because, our microbiomes are constantly changing, it is highly unlikely that there is a perfect, one-size-fits-all composition. Yong explains:

“The microbiome is a teeming collection of thousands of species, all constantly competing with one another, negotiating with their host, evolving, changing. While your genome is the same as it was last year, your microbiome has shifted since your last meal or sunrise. We need to start thinking about it as an ecosystem, like a rain forest or grassland, with all the complexities that entails.”

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