Fermented foods have escaped the health-food shop and landed on burger menus. That is mostly good. Live yoghurt, kefir, sauerkraut and kimchi can bring bacteria, flavour and, in some studies, modest improvements in markers of inflammation. They are food with a past, not a biohack.
They are not interchangeable. A pasteurised ‘kimchi sauce’ is a condiment. A sugary yoghurt drink is a dessert. Salt levels in some ferments are not trivial for people watching blood pressure. As ever, the label is more honest than the halo.
A small trial culture has grown around ‘eat 30 plants a week and a fermented thing’. As slogans go, it is better than most: it points toward fibre and variety. It should not become another way to feel behind.
If you like kefir, drink it. If you do not, lentils will do more for your gut than a fashion you resent. Nutrition is allowed to be optional at the margin.