The Joint Winter Meeting between the Nutrition Society and the Royal Society of Medicine held at The Royal Society of Medicine,
London on 6–7 December 2016
Conference on ‘Diet, nutrition and mental health and wellbeing’
Plenary Lecture: Mental health as an emerging public health problem
Nutritional psychiatry: the present state of the evidence
, Genevieve Moseley
, Michael Berk
and Felice Jacka
School of Allied Health, La Trobe University, Bundoora, Australia
Deakin University, Food & Mood Centre, IMPACT Strategic Research Centre, School of Medicine,
Barwon Health, Geelong, Australia
Department of Psychiatry, University of Melbourne, Parkville, Australia
Orygen, The National Centre of Excellence in Youth Health, Melbourne, Australia
Florey Institute for Neuroscience and Mental Health, Melbourne, Australia
Centre for Adolescent Health, Murdoch Children’s Research Institute, Melbourne, Australia
Black Dog Institute, Sydney, NSW, Australia
Mental illness, including depression, anxiety and bipolar disorder, accounts for a signiﬁcant
proportion of global disability and poses a substantial social, economic and heath burden.
Treatment is presently dominated by pharmacotherapy, such as antidepressants, and psy-
chotherapy, such as cognitive behavioural therapy; however, such treatments avert less
than half of the disease burden, suggesting that additional strategies are needed to prevent
and treat mental disorders. There are now consistent mechanistic, observational and inter-
ventional data to suggest diet quality may be a modiﬁable risk factor for mental illness.
This review provides an overview of the nutritional psychiatry ﬁeld. It includes a discussion
of the neurobiological mechanisms likely modulated by diet, the use of dietary and nutra-
ceutical interventions in mental disorders, and recommendations for further research.
Potential biological pathways related to mental disorders include inﬂammation, oxidative
stress, the gut microbiome, epigenetic modiﬁcations and neuroplasticity. Consistent epi-
demiological evidence, particularly for depression, suggests an association between measures
of diet quality and mental health, across multiple populations and age groups; these do not
appear to be explained by other demographic, lifestyle factors or reverse causality. Our
recently published intervention trial provides preliminary clinical evidence that dietary inter-
ventions in clinically diagnosed populations are feasible and can provide signiﬁcant clinical
beneﬁt. Furthermore, nutraceuticals including n-3 fatty acids, folate, S-adenosylmethionine,
N-acetyl cysteine and probiotics, among others, are promising avenues for future research.
Continued research is now required to investigate the efﬁcacy of intervention studies in large
cohorts and within clinically relevant populations, particularly in patients with schizophre-
nia, bipolar and anxiety disorders.
Diet: Nutrition: Mental health: Psychiatry: Treatment
Mental illness is among the leading causes of disability
worldwide, accounting for 18·9 % of years lived with a
. Due to the high prevalence of common men-
tal disorders, the social, economic and heath burden
associated with these disorders is substantial, with up
to $8·5 trillion in lost output attributed to mental, neuro-
logical and substance use disorders
such as antidepressants, and psychotherapy, such as
*Corresponding author: F. Jacka, email email@example.com
Abbreviations: BDNF, brain-derived neurotrophic factor; NAC, N-acetyl cysteine; RCT, randomised controlled trial.
Proceedings of the Nutrition Society, Page 1 of 10 doi:10.1017/S0029665117002026
© The Authors 2017
Proceedings of the Nutrition Society
cognitive behavioural therapy, are cornerstones of treat-
ment; however, they avert less than half of the disease
burden, suggesting that additional strategies to prevent
and treat mental disorders are needed
. Indeed, recent
evidence suggests that despite a substantial increase in
the use of psychotropics and wider availability of psy-
chotherapies, the population burden of depression has
not reduced, and may be increasing
. If indeed this is
the case, it suggests the presence of operative environ-
mental risk factors for depression.
The new ﬁeld of nutritional psychiatry provides evidence
for diet quality as a modiﬁable risk factor for mental ill-
nesses. Recent systematic reviews examining the association
between diet and common mental disorders have shown
healthy dietary patterns to be inversely associated with the
probability of, or risk for, depression
. Such diets are
characterised by the high intake of vegetables, fruit, whole-
grains, nuts, seeds and ﬁsh, with limited processed foods. In
contrast, unhealthy diets high in processed, high-fat, high-
sugar foods in adolescence and adulthood are shown to be
positively associated with the common mental disorders,
depression and anxiety
. Similar evidence exists in early
childhood, where poor maternal nutrition status and
early-life diet is associated with childhood emotional and
Research investigating the potential biological pro-
cesses involved in the diet and mental health relationship
has primarily implicated inﬂammation, oxidative stress
and neuroplasticity, with the gut microbiome as a key
mediating pathway for each of these processes
An understanding of these pathways has prompted
research into the adjunctive use of dietary and nutraceut-
ical (nutritional supplements) interventions that affect
these pathways for both common and severe psychiatric
disorders; such as n-3 fatty acids in depression and
N-acetyl cysteine (NAC) in schizophrenia
the ﬁrst whole diet intervention studies in clinical depres-
sion are also now available
This review provides an overview of the ﬁeld of nutri-
tional psychiatry including discussion of the implicated
biological mechanisms that are likely modulated by
diet, the results of recent systematic reviews and meta-
analyses regarding the use of dietary and nutraceutical
interventions in mental disorders, and promising avenues
for further research. An executive summary of each sec-
tion can be found in Table 1.
For this narrative review, a systematic literature review
of ﬁve electronic databases (Pubmed, PsychInfo, CiNAHL,
Cochrane Database and Embase) was conducted using key
search terms related to diet (e.g. ‘diet*’,‘nutrition’), nutra-
ceuticals (e.g. ‘diet* supplement’) and mental illness (e.g.
‘depression’,‘mental illness’,‘mood’). Results from system-
atic reviews, notable clinical and observational trials, and
meta-analyses were prioritised for this review.
Implicated pathways in diet and mental illness
There are several pathways implicated in mental illness
and that can be modulated by diet
. This section
will provide an overview of the evidence for the primary
pathways that have been studied to date. Although
described as distinct pathways, it is likely that these path-
ways overlap synergistically and are mutually interacting.
Chronic low-grade inﬂammation, characterised by an
elevationinpro-inﬂammatory cytokines and acute phase
proteins, is implicated in the development of de novo
depression, schizophrenia and bipolar disorder
The causes of this inﬂammation are multifaceted and
include several lifestyle factors, such as psychological
stress, smoking, obesity, lack of sleep and, of particular
relevance to the present discussion, poor diet
from large observational studies suggest that healthy diet-
ary patterns, such as the Mediterranean diet
higher in PUFA, ﬁbre, fruit and vegetables are associated
with lower levels of inﬂammatory markers
Mediterranean dietary patterns signiﬁcantly improve mar-
kers of inﬂammation in intervention studies
Oxidative and nitrosative stress are implicated in several
chronic diseases and appear to be relevant to mental ill-
. Schizophrenic populations have decreased brain
glutathione levels, disordered glutamate metabolism and
increased oxidative stress
. Similar results are reported
in depressed populations, with higher levels of oxidative
stress markers observed, as well as lower levels of antioxi-
dants, such as vitamin E, vitamin C, coenzyme Q10 and
glutathione, when compared with healthy controls
Furthermore, a recent meta-analysis of 115 studies reported
lower antioxidant capacity in depressed patients during
. Given the abundance of antioxidant com-
pounds present in foods such as fruit and vegetables, this is a
pathway that could be modulated through dietary means.
Neurogenesis, particularly within the hippocampus, is
associated with learning, memory and mood regulation,
while altered neurogenesis is implicated in mental ill-
. Brain-derived neurotrophic factor (BDNF) as
well as other neurotrophins (e.g. bcl-2 and vascular endo-
thelial growth factor) are suggested to mediate hippo-
. There is presently limited
clinical investigation of the effect of diet on this pathway;
however, preliminary evidence supports the role of diet in
improving BDNF levels. For example, a 4-week dietary
intervention to increase consumption of carotenoid-rich
fruit and vegetables (eight servings daily) in people
with schizophrenia resulted in higher serum levels of
BDNF than in the control group
. Moreover, an epi-
demiological investigation in older adults has demon-
strated an association between poor diet and reduced
. In addition to possessing anti-
oxidant and anti-inﬂammatory properties, nutrients,
such as n-3 fatty acids
and vitamin E
, can also stimulate neurogenesis while
energy-dense diets high in fat and sugar impair this
W. Marx et al.2
Proceedings of the Nutrition Society
The role of gastrointestinal microbiota on chronic disease
is now a burgeoning area of research. Compelling evi-
dence, predominantly from animal studies, indicates the
gut microbiota can affect mental health-related beha-
viours via multiple pathways
The gastrointestinal microbiota has been implicated in
several neurobiological pathways related to mental
illness, including the modulation of BDNF
, immune function
and the hypothal-
amic–pituitary–adrenal axis-mediated stress response
For example, microbiota-deﬁcient germ-free mice exhibit
Table 1. Executive summary of present research areas within Nutrition Psychiatry
Executive summary Key references
Biological pathways mediating the diet–mental health relationship
Several pathways implicated in mental illness can be modulated by diet. These include pathways related to
inﬂammation, oxidative stress, brain plasticity, mitochondrial dysfunction and the gut–brain axis. Although
described as distinct pathways, it is likely that these pathways overlap synergistically and are mutually
Berk et al.
Moylan et al.
Liu et al.
Zainuddin and Thuret
Fung et al.
Morris and Berk
Maes et al.
Observational data on diet and mental illness in adults
Several meta-analyses and systematic reviews have established a consistent relationship between diet and
depression in adults, across multiple populations, which does not appear to be explained by other demographic
factors or reverse causality
Li et al.
Lai et al.
Psaltopoulou et al.
Childhood and maternal perinatal mental illness observational data
Diet is also associated with mental health in children, adolescents and women in the antenatal period. The body
of research is relatively smaller compared with adult populations; however, research has identiﬁed an inverse
relationship between high-quality diet and mental health disturbances, as well as a positive relationship between
unhealthy diets and mental symptomatology such as internalising and externalising problems in children and
adolescents. Similarly, poor diet quality is associated with antenatal depression; however, evidence for an
association between diet quality and postnatal depression and anxiety is inconsistent
O’Neil et al.
Sparling et al.
Baskin et al.
Speciﬁc dietary patterns, individual nutrients and mental illness
Nutrient dense dietary patterns that include plant foods and high-quality sources of protein are inversely
associated with mental illness, independent of body weight. There is evidence of an association between
depression and dietary patterns, such as a traditional Mediterranean diets, Norwegian diets and Japanese diets
Observational data suggest dietary intake of ﬁsh, magnesium, iron and zinc may be inversely associated with
depression; however, an association with intake of other micronutrients has not been deﬁnitively established
Quirk et al.
Murakami and Sasaki
Li et al.
Li et al.
Evidence from intervention studies
While observational studies have reported consistent evidence for an association between diet quality and
common mental disorders, relatively few intervention studies have investigated this relationship
Present evidence from intervention trials are mixed, with successful trials generally including at least one of the
following: single delivery mode (e.g. single or group face-to-face meetings only), employment of a dietitian,
explicit recommendation of a diet high in ﬁbre and/or fruits and vegetables. The SMILES trial provides
preliminary evidence that dietary interventions in clinically diagnosed depressed populations are feasible and
can provide clinical beneﬁt. Further studies in larger samples are now required to conﬁrm these results
Opie et al.
Jacka et al.
Evidence for the use of nutraceuticals in mental illness
Numerous nutraceutical interventions have been conducted in a range of mentally ill populations, including
depression, bipolar and schizophrenia, with varying levels of efﬁcacy. Supplementation has included ω-3 fatty
acids, vitamins (e.g. B vitamins, vitamin E, C and D), minerals (e.g. zinc, magnesium), herbal preparations (e.g. St
Johns wort, passionﬂower, Kava) and amino acids (e.g. S-adenosylmethionine, N-acetyl cysteine). Presently,
there is a lack of studies that have evaluated the clinical efﬁcacy and safety of these nutraceuticals in populations
with clinical mental disorders. Future studies are required to investigate these interventions using sufﬁciently
powered randomised controlled trial study designs
Cui and Zheng
Sarris et al.
Sarris et al.
Fernandes et al.
Lakhan and Vieira
Firth et al.
Future directions in nutritional psychiatry
Continued research is required to elucidate the impact of various physiological pathways on mental health and to
develop optimal strategies for interventions. In addition, few studies have speciﬁcally considered diet and its
effect on symptomology in patients with severe mental illness
The role of the gut microbiome in mental illness is an emerging area with promise. Further investigation into the
possible role of dietary factors and gut microbiota dysbiosis in psychosis and associated neurodegeneration is
warranted. Furthermore, probiotic supplementation may be an effective nutraceutical intervention; however,
future trials are required to resolve uncertainty regarding the optimal duration of intervention, dose and strains of
N-acetyl cysteine is a promising therapeutic intervention for addiction, bipolar disorder, schizophrenia and
depression. However, while N-acetyl cysteine has been investigated in a range of clinical populations, further
randomised controlled trials are required to conﬁrm these results
Huang et al.
Wallace and Milev
Romijn and Rucklidge
Fernandes et al.
Asevedo et al.
Deepmala et al.
Nutritional psychiatry 3
Proceedings of the Nutrition Society
an exaggerated stress response
and lower BDNF and
serotonin receptor levels in the cortex and hippocampus of
compared with normal gut colonised mice.
At least some of these pathways appear bidirectional, with
stress activation of the hypothalamic–pituitary–adrenal
axis found to modulate microbial composition in rats
Clinically, differences in patterns of faecal microbiota,
reﬂecting decreased gut microbiota richness and diversity,
have been reported in depressed patients compared with
. Transplantation of microbes from
depressed patients into rodents results in depression-
and altering gut microbiota
through probiotic supplementation or food products
inﬂuences depression-related behaviour in animals
Dietary-induced alterations in intestinal permeability
(such as via a high-fat diet
) may also affect mental
health. Integrity of the gut epithelial barrier by tight
junctions regulates the movement of substrates from the
gut into the blood stream and, when compromised, is
associated with depression
. Increased permeability
may allow bacteria-derived lipopolysaccharides to acti-
vate immune cells within the intestinal wall, promoting
the production of inﬂammatory cytokines and activation
of nitro-oxidative stress pathways, resulting in elevated
Impaired mitochondrial energy production, size and distri-
bution are associated with depression, schizophrenia and
may be particularly relevant to bipolar disorder
These changes could be the result of reduced antioxidant
capacity and a pro-inﬂammatory cytokine-mediated
increase in mitochondrial-derived oxygen and nitrogen-free
radicals, suggesting inﬂammation and oxidative stress drive
. Dietary and nutraceutical
compounds such as coenzyme Q10, α-lipoic acid, carnitine,
creatine, resveratrol, NAC and some antidepressants
up-regulate mitochondrial respiratory function in animal
Observational literature on diet and mental illness
There is now consistent epidemiological evidence for an
association between measures of diet quality and mental
health, across multiple populations,
which do not
appear to be explained by other demographic factors or
Several meta-analyses and systematic reviews have estab-
lished a relationship between diet and depression in
. Lai et al.
conducted a meta-analysis
of thirteen observational studies (four cohorts and nine
cross-sectional) and reported that consumption of a
healthy diet was associated with reduced odds of depres-
sion (OR 0·84; 95 % CI 0·76, 0·92). It was, however,
unable to establish a statistically signiﬁcant relationship
between western diet and increased odds of depression,
likely due to insufﬁcient power from the small number
of studies analysed. The second meta-analysis presented
similar results, showing moderate and high adherence
to a Mediterranean diet to be associated with reduced
likelihood of depression
. A more recent systematic
review and meta-analysis including data from twenty-one
studies and 117 229 participants has conﬁrmed an inverse
relationship between dietary patterns characterised by
higher intakes of fruit, vegetables, whole grain, ﬁsh,
olive oil, low-fat dairy and the probability or risk for
depression, and a positive relationship between dietary
patterns characterised by a higher consumption of red
and/or processed meat, reﬁned grains, sweets, high-fat
dairy products and an increased probability or risk of
Childhood and maternal perinatal data
The association between diet and mental health has also
been studied in children, adolescents and women in the
. A systematic review of nine
cross-sectional and three prospective studies reported
an inverse relationship between high-quality diet and
mental health disturbances and a positive relationship
between unhealthy diets and poorer mental health out-
comes in children and adolescents
. Since this system-
atic review, three prospective cohort studies have
reported maternal nutrition and early-life nutrition to
be independently associated with mental symptomatol-
ogy, such as internalising and externalising problems in
children aged 5–7 years, when controlling for prenatal
and postnatal confounders
During pregnancy, women are more susceptible to
nutrient deﬁciencies due to increased physiological stress
on the body and increased nutrient demand from a grow-
ing fetus. These deﬁciencies are likely exacerbated by
poor quality diets. Given the potential role of dietary
nutrients in the biochemical pathways of mental illnesses,
generalised maternal nutrient deﬁciency may explain
rates of perinatal depression. Baskin et al.
ciations between poor diet quality and antenatal depres-
sion; however, evidence was inconsistent for an
association between diet quality and postnatal depression
and anxiety. Together this literature indicates diet is
likely relevant to mental health at all stages of life.
Speciﬁc dietary patterns and individual nutrients
A healthy diet is generally characterised as a higher intake
of fruit, vegetables, ﬁsh and wholegrains, while a western
diet, in contrast, is characterised by higher consumption
of processed foods, processed meats, reﬁned grains, salty
and sugary snacks and beverages
. However, there is
still substantial heterogeneity in deﬁning a healthy diet, as
many unique cultures have diverse but still healthy dietary
. At the core of these diets are nutrient-dense
plant foods and high-quality sources of protein, which
are likely to be a signiﬁcant contributor to the observed
differentiated between a healthy/
traditional diet and a Mediterranean diet, with a
Mediterranean diet having a greater emphasis on high
intake of legumes, moderate intake of meat and dairy,
and olive oil as the main fat source. They reported both
W. Marx et al.4
Proceedings of the Nutrition Society
diets were protective against depression. Observational
studies have examined the association with other diets,
including the traditional Japanese diet
; however, evidence is limited and
It is important to note that the favourable association
of healthy foods and mental health outcomes is consist-
ently independent of the association between unhealthy
foods and poorer mental health outcomes
, which sug-
gests that different physiological pathways may be medi-
ating the potential effects of these contrasting dietary
patterns. These associations are also independent of
body weight, suggesting dietary patterns can affect mental
illness via pathways that are independent of weight status.
A 2010 review of thirty-four publications investigating
a number of dietary variables, including long chain n-3
PUFA, ﬁsh, folate and B vitamins as markers of dietary
intake, did not establish a deﬁnitive association between
the intake of speciﬁc dietary components and depressive
. However, more recent meta-analyses of
observational studies have identiﬁed ﬁsh consumption,
and dietary magnesium, iron and zinc as associated
with lower rates of depression
While most observational studies have made appropri-
ate adjustments for potential confounding variables, such
as socioeconomic status, physical activity and smok-
, residual confounding by these variables is likely.
Moreover, while reverse causality has been examined as
an explanatory factor (e.g.
), observational studies,
particularly when cross-sectional, are unable to establish
causality. Therefore, observational studies using pro-
spective and case–control cohorts and intervention ran-
domised controlled trials (RCT) should be prioritised in
future studies. Most studies to date have examined the
association between diet and depression, with only a lim-
ited exploration of anxiety and more severe mental ill-
nesses, such as schizophrenia and bipolar disorder.
There is now a need to extend observational nutritional
psychiatry research into these areas.
Dietary interventions for mental illness
While observational studies have reported consistent
evidence for an association between diet quality and
common mental disorders, there are relatively few inter-
ventions that have investigated this relationship. Our
2013 systematic review of seventeen previous interven-
tion studies provides an overview of existing dietary
intervention studies with depression, anxiety and mood
. The results were mixed, with
approximately half the studies reporting improvements
in outcomes, with successful trials generally including
at least one of the following: single delivery mode (e.g.
single or group face-to-face meetings only), employment
of a dietitian, explicit recommendation of a diet high in
ﬁbre and/or fruit and vegetables. These trials were also
less likely to recommend weight loss, reduce red meat
intake or follow a low-cholesterol diet.
The review also identiﬁed multiple limitations within
the literature. Primarily, only one study recruited
participants with a depressive/anxiety diagnosis, while
others included other participant populations, such as
breast cancer and obese/overweight participants, and/or
excluded participants with pre-existing mental health
symptoms or disorders. Some studies included only one
gender or had a sample comprising primarily Caucasian
adults with a high education level. Hence, the ﬁndings
may not be generalisable to other clinical and general
Since the publication of this review, the potential
impact of a Mediterranean diet on the incidence of de
novo depression has been assessed in a post hoc analysis
of the PREDIMED study
; this was a large RCT that
investigated the effect of Mediterranean diet on CVD
endpoints. While underpowered for the depression end-
point, the analysis suggested a non-signiﬁcant reduction
in the incidence of de novo depression for those rando-
mised to a Mediterranean diet with nuts, and signiﬁcant
reduction in a subset of those with type 2 diabetes.
Forsyth et al.
conducted a 12-week RCT in 119
individuals treated for depression and/or anxiety in pri-
mary care. The intervention group received motivational
interviewing, activity scheduling and an individualised
lifestyle programme focusing on changes in physical
activity and diet (e.g. reducing fat intake, increasing vege-
table intake and variety). The control group received
regular phone contact with research staff that did not
include dietary advice but asked participants about
changes to their diet or physical activity patterns. Both
groups reported improved symptoms of depression and/
or anxiety as well as dietary intake over time. However,
no signiﬁcant differences in symptoms were observed
between the two groups.
We have recently published the results of the SMILES
trial, an RCT that investigated a 12-week modiﬁed
Mediterranean diet intervention in sixty-seven participants
with major depression
. Participants in the intervention
group received personalised dietary and nutritional coun-
selling based on a traditional Mediterranean diet and the
Australian Dietary Guidelines. Participants in the control
group received the same number of scheduled visits but
received a ‘befriending’protocol (social support) whereby
research staff met with participants and discussed neutral
topics of interest (e.g. sport, hobbies). At 12 weeks, there
was a signiﬁcantly greater improvement in depression
scores in the dietary support group compared with the
social support control group. Furthermore, there was a
signiﬁcantly greater level of remission in the dietary sup-
port group (deﬁned as a Montgomery–Åsberg
Depression Rating Scale score <10) with 32·3% (n10/
31) of the dietary support group reporting remission com-
paredwith8·0% (n2/25) in the social support control
group and a number needed to treat of 4·1. Participants
did not signiﬁcantly change their energy intake or body
weight during the trial, which suggests that these improve-
ments were not primarily related to weight status. The
results of the SMILES trial provide preliminary evidence
that dietary interventions in clinically diagnosed popula-
tions are feasible and can provide clinical beneﬁt.
Further studies in larger samples are now required to
conﬁrm these results.
Nutritional psychiatry 5
Proceedings of the Nutrition Society
Nutraceutical interventions for mental illness
There is a broad array of nutraceutical interventions that
target pathways implicated in mental illness, including
inﬂammation, oxidative stress, modulation of the methy-
lation cycle and prevention of hippocampal-associated
cognitive decline, as well as mitochondrial dysfunction
and neurotransmitter pathways
. Due to their action
on these pathways, clinical trials have investigated
speciﬁc nutrients and herbal preparations for their effect
on mental illness. As this area of research is expansive,
this section will only provide an overview of recent sys-
tematic reviews and meta-analyses that have evaluated
intervention studies in this area.
St John’s Wort, a widely researched herbal nutraceut-
ical, has been reported in a recent meta-analysis to
achieve similar improvements in depression to selective
serotonin reuptake inhibitor medication controls
The n-3 PUFA are another supplement that have a
long history of investigation, with several meta-analyses
reporting mixed ﬁndings
. However, interventions
that use n-3 formulations with a high EPA : DHA ratio
as an adjunctive to antidepressants might be beneﬁcial
to patients with depression
methylfolate and vitamin D may also have a positive
effect on depression as adjunctive interventions, although
there are also large negative studies
some nutraceuticals, including creatine, folinic acid and
an amino acid combination, have yielded positive prelim-
inary data from single trials, while zinc, folic acid, vita-
min C, inositol and tryptophan have mixed or
non-signiﬁcant effects for depression
. The results of
additional meta-analyses also report no beneﬁt from fol-
ate, vitamin B
and vitamin D supplementation for
While not as extensively studied, clinical trials have
also investigated some nutraceuticals for other mental ill-
nesses. Three meta-analyses concluded that adjunctive
n-3 supplementation can be beneﬁcial for both unipolar
and bipolar depressions
. The results of a recent
meta-analysis suggest that NAC may be efﬁcacious for
depression and depressive symptoms regardless of the
main clinical diagnosis, although again there are negative
. Furthermore, L-tryptophan, magnesium, folic
acid and branched-chain amino acids may be effective
for bipolar disorder-related mania and chelated mineral
and vitamin formulas may be effective in improving
both bipolar disorder-related depression and mania
The use of micronutrient combinations for mental ill-
ness has also been investigated. A systematic review by
Rucklidge and Kaplan
reported limited evidence for
micronutrient combinations for stress, antisocial beha-
viours and depressed mood in healthy people, as well
as potentially for attention-deﬁcit hyperactive disorder
and autism. However, the review identiﬁed few studies
in this area and most studies were conducted in healthy
rather than clinically diagnosed populations.
A 2010 systematic review concluded that passionﬂower,
kava and combinations of L-lysine and L-arginine were
promising interventions for anxiety and that more
research is required to make recommendations regarding
magnesium supplementation due to limited published
studies on this intervention. The results of a meta-analysis
reported that folate and other vitamin B supplementation
) may be beneﬁcial for certain popu-
lations diagnosed with schizophrenia
Nutraceuticals including n-3 fatty acids, calcium,
multivitamin and B vitamins have been investigated for
perinatal depression; however, a recent review concluded
that there is presently limited support for nutraceutical
interventions in this population with few intervention
studies reporting signiﬁcant improvements and several
trials rated as having a medium or high risk of bias
Overall, clinical trials have evaluated numerous nutra-
ceutical interventions; however, there is a lack of trials
that have evaluated their clinical efﬁcacy and safety in
populations with clinical mental disorders. Future studies
are required to investigate these interventions using sufﬁ-
ciently powered RCT study designs. Importantly, likely
effect modiﬁers, including baseline diet, inﬂammatory
status and gut microbiome composition, are essential
variables to include in future interventions.
Promising new avenues for investigation
The ﬁeld of nutritional psychiatry has provided a signiﬁ-
cant body of evidence to suggest that dietary patterns are
relevant to common mental illnesses. However, contin-
ued research is required to translate the evidence base
into clinical and public health recommendations.
Dietary patterns may modulate numerous biological
pathways involved in mental illness including inﬂamma-
tion, oxidative stress, the gut–brain axis and neurogen-
esis. Continued research is required to elucidate the
impact of these as well as additional pathways, including
the role of homocysteine
, on mental health and to develop optimal strategies
Most observational data to date have focused on com-
mon mental disorders and there is now a need to examine
dietary patterns in those with severe mental illnesses.
Numerous systematic reviews and meta-analyses have
considered the effects of dietary patterns on weight loss
and metabolic diseases in individuals with severe mental
illnesses, namely schizophrenia and bipolar disorder, yet
few have speciﬁcally considered diet and its possible
effect on psychiatric symptoms in these populations.
Limited evidence suggests a positive association between
obesity/weight gain and impaired functioning in indivi-
duals with bipolar disorder; however, the directionality
of this relationship has not been ﬁrmly established, indi-
cating the need for further research in this area
Schizophrenia is associated with gastrointestinal and
microbial dysfunction, immune and inﬂammatory
. Further investigation into the possible
role of dietary factors and gut microbiota dysbiosis in
psychosis and associated neurodegeneration is warranted.
The microbiota–gut–brain diet axis is a promising tar-
get that could be modiﬁed via dietary and nutraceutical
intervention, such as prebiotics (e.g. high-ﬁbre foods
and supplements) and probiotics (e.g. fermented foods
W. Marx et al.6
Proceedings of the Nutrition Society
or supplements) directly targeting microbial populations.
A 2015 systematic review of ten RCT investigated pro-
biotic supplements for stress, mood, anxiety, schizo-
phrenic symptoms and externalising behaviours in
autism spectrum disorder. It concluded that few studies
reported signiﬁcant improvements from probiotic supple-
mentation. Alternatively, a more recent meta-analysis of
ﬁve RCT reported that probiotic supplementation
decreased measures of depression (−0·30, 95 % CI
−0·51, −0·09; P=0·005)
, and an additional system-
atic review of ten RCT also concluded that probiotics
may be beneﬁcial to cognition, mood and anxiety
However, few studies included in these reviews were con-
ducted within populations with diagnosed mental illness
and the clinical relevance to psychiatry is thus far
unclear. Furthermore, all studies noted additional limita-
tions in the literature including uncertainty regarding the
optimal duration of intervention, dose and strains of the
. Future quality intervention studies are
required to improve the existing evidence base for pro-
biotic supplementation and to explore the role of dietary
manipulation (e.g. pro and prebiotic foods) on mental
health. Characterisation of changes in microbial signa-
ture and composition and gut permeability in response
to diet, and associated changes in mental health and
related behaviours are also needed.
NAC is an amino acid-derived glutathione precursor
that may modulate glutamatergic and neurotrophic
transmission, glutathione production for antioxidant
capacity, mitochondrial function and inﬂammation
Recent reviews conclude that, while the present evidence
is preliminary, NAC is a promising therapeutic intervention
for addiction (e.g. substance dependence, gambling) and
bipolar, schizophrenic and depressed populations
However, while NAC has been investigated in a range of
these clinical populations, further RCT are required to
conﬁrm these results
Nutritional psychiatry is a rapidly growing ﬁeld of
research that has the potential to provide clinically mean-
ingful interventions to both prevent and manage mental
illness. Observational research has demonstrated a con-
sistent relationship between diet quality and common
mental illnesses, while biological pathways including
inﬂammation, oxidative stress, gastrointestinal micro-
biota and neurotrophic factors provide viable mechan-
isms of action for this observed effect. Preliminary
clinical evidence provides support for the feasibility and
efﬁcacy of dietary and some nutraceutical interventions.
It is likely that changes to public policy are needed to
translate these ﬁndings into population-wide changes in
eating behaviour to achieve associated beneﬁts
More research is now required to investigate the efﬁcacy
of intervention studies in large cohorts and within clinic-
ally relevant populations, particularly in patients with
schizophrenia, bipolar and anxiety disorders, in order
to build on the existing evidence base and to inform clin-
M. B. is supported by an NHMRC Senior Principal
Research Fellowship (1059660). F. J. is supported by an
NHMRC Career Development Fellowship (2) (1108125).
Conﬂicts of Interest
W. M. and G. M. contributed equally, with primary
responsibility for writing this work. M. B. and F. J. con-
tributed to planning and editing this work.
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