India, Oct. 14 -- The same microbial preparation can reach an Indian consumer as a food, as a nutraceutical, or as an investigational medicine. The science underneath does not change. What changes is the evidence asked of it, the authority that asks, and the claims the label is then permitted to carry.

For most of the past decade that was tolerable. Probiotics were live organisms sold as supplements, medicines were medicines, and the ground between them was wide enough that few products had to stand in it. Then the field moved, and it moved in a particular direction.

The turn from organism to metabolite

Much of what the microbiome does for its host, it does chemically. Bacteria ferment what we cannot digest and release compounds the ho...