Column: Dr's Casebook: Dr Keith Souter: Fermented food in diet may protect the gut and help the mood
Fermented foods are considered staples in many countries around the world. Nowadays fermented drinks like Kombucha and Kefir have become extremely popular and are often promoted for their health-giving benefits. New research suggests that sauerkraut, which is essentially fermented cabbage, could be protective to the gut, help digestion and protect against a number of illnesses.
A study from the University of California has looked at what happens in the process of fermentation and whether the metabolites in sauerkraut are very different to those found in raw cabbage. But specifically, they wanted to test whether the nutrients in sauerkraut protect the gut cells from inflammation. To do so they compared the effect on intestinal cells of raw cabbage, sauerkraut and the liquid brine left behind from the fermentation process. They found that sauerkraut helped maintain the integrity of intestinal cells, while raw cabbage and brine did not.
On analysing the changes that take place during fermentation of cabbage they found that fermentation produced several hundred metabolites including lactic acid and several amino acids that are known to be beneficial to the gut cells. The fact that a lot of these are the same as metabolites produced by the gut microbiome, that is the microflora within the bowel suggests that this can only be beneficial to the gut cells.
One of the amino acids produced is tryptophan, which is key to the production of serotonin, a neurotransmitter or messenger chemical in the brain which influences several aspects of brain function, including mood. Among the hundreds of other metabolites produced by fermentation there may also be other potential brain neurotransmitters in a raw form.
Making sauerkraut is relatively simple and only takes between one and four weeks. But the researchers say they found no real difference between shop bought and lab prepared sauerkraut. They suggest that adding a regular serving of sauerkraut in the diet may keep the gut healthy and reduce inflammation.
Other research from the University of Cork in Ireland has been comparing sequencing data from over 200 fermented foods from all over the world. They have looked for a whole range of these potential neurotransmitters that may have a positive impact on brain and mental health. So far they have found that out of these 200 fermented foods, almost all of them showed the ability to exert some sort of potential to improve gut and brain health.