In this discussion, we may unwittingly give the impression
that fermentation is exclusively a beneficial application
to food and beverage production. Such is not the
case and not all forms of fermentation or fermented foods
can be painted with the same brush. For example, certain
microorganisms (for example, fungi) associated with
pickled foods may enhance the production of N-nitroso
compounds with potential carcinogenic properties [164].
Also, although agmatine and other polyamines found in
fermented meats, fish, and certain beverages have been
shown to have a variety of experimental benefits related
to brain health [165,166], a safe level of intake remains
unknown [165]. However, as outlined in our review,
there is more than ample justification to follow the
microbe-nutrition and gut-brain research pathways into
convergence. The clinical world of mental health involves
one where consumption of convenient, high-fat, or
high-sugar foods is the norm; these foods, at odds with
our evolutionary past, are not only undermining optimal
nutritional status, they have untold effects on the microbiome
and ultimately the brain. Hopefully, further research