Fermented foods, from sourdough to kombucha, may be terribly trendy right now but it appears they can cause some deeply unfashionable side-effects.
These include bloating, headaches and allergies, a microbiologist has warned.
Fermentation has been used for thousands of years to preserve foods from yoghurt to sauerkraut.
However, it has become especially fashionable in recent years because of supposed "probiotic" benefits to our digestion.
Among the latest fermented foods popular with the health-conscious is kombucha, which is a mix of yeast and bacteria fermented with black or green tea, and kefir, a fermented milk drink.