You are legion. So am I. The average human is made up of many trillions of cells. But you and I depend on many trillions more, in the form of bacteria that live in our guts.

Scientists have known for donkey’s years that those bugs exist. But it is only in the past decade or so that they have started to understand just how important they are. Besides breaking down some bits of food for you, your gut bacteria—your microbiome, as they have come to be called—also keep disease-causing bugs in check and even help to regulate behaviour (the brain and the gut are deeply connected).

No sooner had all this become clear than some people began to wonder whether one’s microbiome could be “optimised”. Cue the emergence of a whole new wellness fad, the subject of this week’s column.

As ever, you’ll have to read the piece if you want the full story. But the quick version is that, as so often in the wellness industry, many of the companies promoting the idea are way out over their skis. There is no such thing as an “ideal” microbiome to aim for, for one thing. For another, many firms seem unable to reliably manage even the basic task of assessing their customers’ microbiomes properly. Our verdict? Save your money.

What’s your secret to a healthy gut? Please vote in our poll below. And if you have more views, tips or tricks, please write to us at wellinformed@economist.com. We might feature you in next week’s newsletter. See you then.

The trillions of bugs in a human gut digest complex carbohydrates into fatty acids that provide about 10% of an individual’s calories. They synthesise vitamins, notably K (which regulates blood clotting) and various members of the B group. They help tune the immune system. They suppress the growth of pathogens. And they regulate production of signalling molecules, such as serotonin, involved in sending messages from the gut to the brain.