Background: There is mounting interest in the potential efficacy of low carbohydrate and very low carbohydrate ketogenic diets in various neurological and psychiatric disorders.Aims: To conduct a systematic review and narrative synthesis of low carbohydrate and ketogenic diets (LC/KD) in adults with mood and anxiety disorders.Method: MEDLINE, Embase, PsycINFO and Cochrane databases were systematically searched for articles from inception to 6 September 2022. Studies that included adults with any mood or anxiety disorder treated with a low carbohydrate or ketogenic intervention, reporting effects on mood or anxiety symptoms were eligible for inclusion. PROSPERO registration CRD42019116367.Results: The search yielded 1377 articles, of which 48 were assessed for full-text eligibility. Twelve heterogeneous studies (stated as ketogenic interventions, albeit with incomplete carbohydrate reporting and measurements of ketosis; diet duration: 2 weeks to 3 years;n= 389; age range 19 to 75 years) were included in the final analysis. This included nine case reports, two cohort studies and one observational study. Data quality was variable, with no high-quality evidence identified. Efficacy, adverse effects and discontinuation rates were not systematically reported. There was some evidence for efficacy of ketogenic diets in those with bipolar disorder, schizoaffective disorder and possibly unipolar depression/anxiety. Relapse after discontinuation of the diet was reported in some individuals.Conclusions: Although there is no high-quality evidence of LC/KD efficacy in mood or anxiety disorders, several uncontrolled studies suggest possible beneficial effects. Robust studies are now needed to demonstrate efficacy, to identify clinical groups who may benefit and whether a ketogenic diet (beyond low carbohydrate) is required and to characterise adverse effects and the risk of relapse after diet discontinuation.

Diet quality is associated with depression risk, however the possible role of dairy products in depression risk is unclear. A number of epidemiological studies have examined associations between dairy consumption and depressive symptoms, but results have been inconsistent. Therefore, this systematic review aimed to examine whether an association exists between dairy consumption and depressive symptoms or disorders in adults. Anxiety symptoms were also explored as a secondary outcome. CINAHL, Cochrane, MEDLINE complete, EMBASE, Scopus and PsycINFO databases were searched from database inception to December 2018. Studies were included if they used a case-control, cross-sectional, or cohort study design, and included community dwelling or institutionalized adults (≥18 years). Seven prospective and six cross-sectional studies (N = 58,203 participants) reported on the association between dairy consumption and depressive symptoms or disorders. Findings were mixed, with one study reporting a positive association; five studies reporting no association; and seven studies reporting mixed associations depending on dairy type, gender or population group. We found conflicting and inconsistent associations in studies that were generally of fair quality. Future longitudinal and intervention studies that employ more rigorous dietary assessment methods are warranted.

Purpose: Evidence on the association between dairy intake and depression is conflicting. Given numerous dietary guidelines recommend the consumption of low-fat dairy products, this study examined associations between total dairy, high-fat dairy, and low-fat dairy intake and the prevalence of elevated depressive symptoms. Associations between dairy products, which differed in both fat content and fermentation status, and depressive symptoms were also explored. Methods: This cross-sectional study included 1600 Finnish adults (mean age 63 ± 6 years; 51% female) recruited as part of the Kuopio Ischaemic Heart Disease Risk Factor Study. Dairy intake was assessed using 4-day food records. Elevated depressive symptoms were defined as having a score ≥ 5 on the Diagnostic and Statistical Manual of Mental Disorders-III Depression Scale, and/or regularly using one or more prescription drugs for depressive symptoms. Results: In total, 166 participants (10.4%) reported having elevated depressive symptoms. Using multivariate logistic regression models, intake in the highest tertile of high-fat dairy products (OR 0.64, 95% CI 0.41–0.998, p trend = 0.04) and high-fat non-fermented dairy products (OR 0.60, 95% CI 0.39–0.92, p trend = 0.02) were associated with reduced odds for having elevated depressive symptoms. Whereas no significant association was observed between intake of total dairy, low-fat dairy, or other dairy products, and depressive symptoms. Conclusion: Higher intake of high-fat dairy and high-fat non-fermented dairy products were associated with reduced odds for having elevated depressive symptoms in middle-aged and older Finnish adults. Given the high global consumption of dairy products, and widespread burden of depression, longitudinal studies that seek to corroborate these findings are required.

Despite the putative health benefits of fermented dairy products, evidence on the association between fermented dairy and non-fermented dairy intake and depression incidence is limited. This study examined cross-sectional and prospective associations between total dairy, fermented dairy, and non-fermented dairy intake with 1) the presence of elevated depressive symptoms and 2) the risk of a future hospital discharge or outpatient diagnosis of depression. Data from 2603 Finnish men (aged 42–60 years), recruited as part of the Kuopio Ischaemic Heart Disease Risk Factor Study, were included. Multivariable logistic regression models were used to examine odds ratios (ORs) and 95% confidence intervals (CIs) for elevated depressive symptoms (Human Population Laboratory Scale ≥ 5 points) at baseline. Cox proportional hazard's regression models were used to estimate hazards ratios (HRs) and 95% CIs between dairy categories and risk of depression diagnoses. In cross-sectional analyses, fermented dairy intake in the highest (vs lowest) tertile was associated with lower odds for having elevated depressive symptoms (adjusted-OR 0.70, 95% CI 0.52–0.96). Each 100g increase in non-fermented dairy intake was associated with higher odds for having elevated depressive symptoms (adjusted-OR 1.06, 1.01–1.10). During a mean follow-up time of 24 years, 113 males received a diagnosis of depression. After excluding cheese intake, higher fermented dairy intake was associated with a lower risk of depression diagnosis (adjusted-HR 0.62, 0.38–1.03), which was strengthened after excluding those with elevated depressive symptoms at baseline (adjusted-HR 0.55, 0.31–0.99). Whereas non-fermented dairy intake in the highest tertile was associated with a two-fold higher risk of depression (adjusted-HR 2.02, 1.20–3.42). Fermented dairy and non-fermented dairy intake were differentially associated with depression outcomes when examined cross-sectionally and over a mean period of 24 years. These findings suggest that dairy fermentation status may influence the association between dairy intake and depression in Finnish men.

Background: Beta-casein is a major protein in cow’s milk, of which A1 and A2 are the most frequent variants. Recent evidence implicates A1 beta-casein consumption in mechanisms that are of potential importance to mental health, yet its possible effects on psychological endpoints remains unknown. The primary aim of the study is to evaluate the comparative effects of consumption of dairy products containing A2 beta-casein versus conventional dairy (i.e. containing both A1 and A2 beta-casein) on symptoms of psychological distress in women with low mood. Methods: ‘The Moo’D Study’ is a 16-week, superiority, 1:1 parallel group, triple-blinded, randomised controlled trial. Ninety women with low mood (Patient Health Questionnaire score ≥ 5) will be randomised to consume either A2 beta-casein only or conventional dairy products. The primary outcome, symptoms of psychological distress, will be measured by the 21-item Depression, Anxiety and Stress Scale. Secondary outcomes will include symptoms of depression, anxiety and stress, severity of low mood, cognition, gut microbiota composition, gut symptomatology, markers of immune function, gut inflammation, systemic metabolites, endothelial integrity and oxidative stress, body composition, perceived wellbeing, sleep, quality of life, resource use and cost-effectiveness. Discussion: This study will advance our understanding of the possible impact of milk proteins on psychological distress in women as well as elucidate mechanisms underpinning any association. Given dairy products form a substantial component of traditional and Western diets, the implications of these findings are likely to be of clinical and public health importance. Trial registration: The trial protocol has been prospectively registered with the Australia and New Zealand Clinical Trials Registry, ACTRN12618002023235. Registered on 17 December 2018.