Plant power? A systematic review of the effects of plant-based diets on people with mental illness

Objective There is increasing interest in plant-based diets in the general population and an increasing evidence base for the positive impact of plant-based diets on health outcomes for many chronic diseases. This systematic review aims to identify the effects of plant-based diets on people with mental health conditions. Methods A systematic review of intervention and observational studies. We conducted a systematic electronic search of MEDLINE (Ovid), EMBASE (Ovid), PsycINFO (ProQuest), British Nursing Index (ProQuest), CINAHL (EBSCO) and the Cochrane library to April 2019, with no date limits. We extracted data on outcomes and assessed the studies for bias using validated tools. Results We retrieved 588 studies. One study met the inclusion criteria with high risk of bias. The intervention was a plant-based diet for people with moderate to severe depression, without a control group. The study recruited 500 people, but recorded 66.8% attrition. Of the completers, 62% reported improvements in depressive symptoms, and 59% in anxiety symptoms. Completers lost 5.7lbs (2.6kg) during the trial and 15lb (6.8kg) at six month follow up. Conclusion There is not enough research to make conclusions about the effects of plant-based diets on people with mental health conditions. Given the evidence for positive effects of plant-based diets on physical health, further research is urgently required to understand the effects on people with mental health conditions. This will support the provision of advice and guidance for patients with mental illness who want to optimise their diet to improve their mental and physical health. PROSPERO registration CRD42019133440 ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement No external funding was received. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: No ethical approval was required. All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes No additional data is available.