The potential of fermented foods
Thus far, we have highlighted that depression and other
mental health disorders are characterized by chronic,
low-grade inflammation and oxidative stress. Conversely,
a traditional diet rich in antioxidant, anti-inflammatory
foods may confer some level of protection against depression.
We have also noted that an intestinal ‘inflammatory
microbiome’ appears to exist, one that may contribute to
altered mood via intestinal permeability, systemic LPS
burden, and even direct-to-brain microbe communication.
Such an inflammatory microbiome may be facilitated, at
least in part, by Western dietary habits. Research shows
that high-fat or high-sugar and low nutrient-value foods are
commonly consumed by those with depression, anxiety,
and high levels of chronic distress [123-125], thus contributing
to the likelihood of an inflammatory microbiome.
Preliminary research in rodents and human beings suggests
that the behavioral consequences of an inflammatory
microbiome can be offset by the administration of beneficial
microbes. All this leads us full circle to the ancient Neolithic
vessels in asking to what extent fermented foods or beverages
might contribute to mental health. We are certainly
not the first to ask this question in the broad sense; in 1938,
Lloyd Arnold, MD, aptly a professor of both preventive
medicine and bacteriology at the University of Illinois, pondered
to what extent ancient diets, fermented foods, and
their effect on the ‘bacterial flora of the intra-intestinal contents’
converged to promote health [126].
Today, scientific advances allow for some answers in
the direction toward the potential of fermented foods. It
is well established that with traditional dietary patterns,
fermentation can magnify protein quality [127] and the
bioavailabity of mood-regulating B vitamins, magnesium,
and zinc [128-131]. The effect of diet on intestinal
microbiota may also extend to vitamin D levels [132].
However, it is also becoming clear that the Lactobacillus
species isolated from traditional fermented foods are
biologically active in other ways, for example, upon oral
consumption, Lactobacillus plantarum strains isolated
from traditional Chinese fermented foods provide strong
antioxidant protection in animals [133]. Fermentation of
fruit and herbal smoothies with Lactobacillus plantarum
and other strains has been shown to preserve their polyphenolic
compounds and vitamin C, and as expected, this
enhances subsequent free radical scavenging activity that
would otherwise be lost with storage [134]. Fermented
soymilk also has a more pronounced antioxidant capacity
than unfermented soymilk, and this activity is further
enhanced by the synergistic application of both lactic
acid bacteria and bifidobacteria together versus only
Lactobacilli or Bifidobacterium strains alone [135].
The fermentation of fiber-rich components of traditional
diets, such as, soy germ, wheat germ, rice bran,
or breads made via traditional fermentation techniques,
have been shown to produce novel bioactive compounds
capable of producing beneficial immune, glycemic, and
anti-inflammatory activities [136-139]. In the case of
fermented rice bran, where enhanced phenolic availability
has been noted, there is specific experimental
evidence indicating beneficial mental properties via the
bioactive compounds. More specifically, compared with
controls, oral administration of fermented rice bran extract
reduced experimental fatigue and stress [140,141].
Fermentation of rice bran, and other traditional foods,
such as mung beans, buckwheat sprouts, and lentils, is
known to increase the available GABA content significantly
[142-144]. Whereas synthetic GABA in oral form
has been classically dismissed as of limited benefit due
to absorption issues, research has reported value of the
oral administration of GABA derived from Lactobacillus
hilgardii fermentation in anxiety reduction in human
beings, and antidepressant activity via the administration
of GABA-rich red yeast rice [145,146].
Recent evidence suggests that the health-promoting
target of flavonoids is directed toward the human gut
bacterial metagenomes, and that these benefits have an
evolutionary origin. Functional analysis using clusters of
orthologous groups of bacteria target proteins suggests
that flavonoids regulate the metabolism of gut microbiota
[147]. Experimental research has shown that when common
dietary polyphenols are subjected to fermentation,
the newly formed biotransformation phytochemicals are
more capable of causing a beneficial shift in microbial
growth stimulation [148]. In positioning fermented foods
The potential of fermented foodsThus far, we have highlighted that depression and othermental health disorders are characterized by chronic,low-grade inflammation and oxidative stress. Conversely,a traditional diet rich in antioxidant, anti-inflammatoryfoods may confer some level of protection against depression.We have also noted that an intestinal ‘inflammatorymicrobiome’ appears to exist, one that may contribute toaltered mood via intestinal permeability, systemic LPSburden, and even direct-to-brain microbe communication.Such an inflammatory microbiome may be facilitated, atleast in part, by Western dietary habits. Research showsthat high-fat or high-sugar and low nutrient-value foods arecommonly consumed by those with depression, anxiety,and high levels of chronic distress [123-125], thus contributingto the likelihood of an inflammatory microbiome.Preliminary research in rodents and human beings suggeststhat the behavioral consequences of an inflammatorymicrobiome can be offset by the administration of beneficialmicrobes. All this leads us full circle to the ancient Neolithicvessels in asking to what extent fermented foods or beveragesmight contribute to mental health. We are certainlynot the first to ask this question in the broad sense; in 1938,Lloyd Arnold, MD, aptly a professor of both preventivemedicine and bacteriology at the University of Illinois, ponderedto what extent ancient diets, fermented foods, andtheir effect on the ‘bacterial flora of the intra-intestinal contents’converged to promote health [126].Today, scientific advances allow for some answers inthe direction toward the potential of fermented foods. Itis well established that with traditional dietary patterns,fermentation can magnify protein quality [127] and thebioavailabity of mood-regulating B vitamins, magnesium,and zinc [128-131]. The effect of diet on intestinalmicrobiota may also extend to vitamin D levels [132].However, it is also becoming clear that the Lactobacillusspecies isolated from traditional fermented foods arebiologically active in other ways, for example, upon oralconsumption, Lactobacillus plantarum strains isolatedfrom traditional Chinese fermented foods provide strongantioxidant protection in animals [133]. Fermentation offruit and herbal smoothies with Lactobacillus plantarumand other strains has been shown to preserve their polyphenoliccompounds and vitamin C, and as expected, thisenhances subsequent free radical scavenging activity thatwould otherwise be lost with storage [134]. Fermentedsoymilk also has a more pronounced antioxidant capacitythan unfermented soymilk, and this activity is furtherenhanced by the synergistic application of both lacticacid bacteria and bifidobacteria together versus onlyLactobacilli or Bifidobacterium strains alone [135].The fermentation of fiber-rich components of traditionaldiets, such as, soy germ, wheat germ, rice bran,or breads made via traditional fermentation techniques,have been shown to produce novel bioactive compoundscapable of producing beneficial immune, glycemic, andanti-inflammatory activities [136-139]. In the case offermented rice bran, where enhanced phenolic availabilityhas been noted, there is specific experimentalevidence indicating beneficial mental properties via thebioactive compounds. More specifically, compared withcontrols, oral administration of fermented rice bran extractreduced experimental fatigue and stress [140,141].Fermentation of rice bran, and other traditional foods,such as mung beans, buckwheat sprouts, and lentils, isknown to increase the available GABA content significantly[142-144]. Whereas synthetic GABA in oral formhas been classically dismissed as of limited benefit dueto absorption issues, research has reported value of theoral administration of GABA derived from Lactobacillushilgardii fermentation in anxiety reduction in humanbeings, and antidepressant activity via the administrationof GABA-rich red yeast rice [145,146].Recent evidence suggests that the health-promotingtarget of flavonoids is directed toward the human gutbacterial metagenomes, and that these benefits have anevolutionary origin. Functional analysis using clusters oforthologous groups of bacteria target proteins suggeststhat flavonoids regulate the metabolism of gut microbiota[147]. Experimental research has shown that when commondietary polyphenols are subjected to fermentation,the newly formed biotransformation phytochemicals aremore capable of causing a beneficial shift in microbialgrowth stimulation [148]. In positioning fermented foods
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