Influence of Lycopene Intake on Mental Health: A Systematic Review of Randomized Controlled Trials (RCTs)

Background/Objectives: The potential influence of lycopene on mental health was indicated in some studies, but it was not summarized within any systematic review so far. The aim of the presented study was to analyze the influence of lycopene on mental health within a systematic review of Randomized Controlled Trials (RCTs). Methods: The study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and it was based on PubMed, Web of Science, Cochrane, and Google Scholar databases, while the RCTs published until February 2025 were included. The systematic review was registered within the database of the International Prospective Register of Systematic Reviews (PROSPERO) (CRD420250650525). The studies were considered where the adult population was studied; intervention was based on oral lycopene intake in any form (lycopene supplement, lycopene-enriched functional food, or regular food product being an important source of lycopene); lycopene intake of a specified dose was applied; any mental health result was studied using a valid psychological measure. After duplicate removal, 642 studies were screened, and finally, six RCTs were included and assessed using the revised Cochrane risk-of-bias tool for randomized trials, while various mental health outcomes were allowed (excluding subjects with intellectual disabilities, eating disorders, and neurological disorders). Each stage of screening, inclusion, reporting, and assessment was conducted independently by two researchers. Results: The included studies were conducted in populations of healthy individuals (one study), but mainly in individuals with various diseases: Benign Prostatic Hyperplasia (BPH) (two studies), Burning Mouth Syndrome (BMS) (one study), xerostomia (one study), and infertility (one study). Within the included studies, various lycopene sources were applied, including lycopene supplements, functional foods, and regular food products, as well as various lycopene doses from 1.35 mg to 27.8 mg per day. The included studies assessed quality of life (five studies), depression and anxiety (two studies), stress (two studies), and mood states (one study). In spite of the fact that all six included studies were RCTs, the comparison between the intervention group and placebo group was made in only four studies, and none of them stated the difference between the compared groups. A low risk of bias was concluded for three studies (all of them not confirming the influence of lycopene on mental health), and a high risk of bias was found in three studies (one of them not confirming, and two not conclusive). Conclusions: The evidence gathered within the systematic review of RCTs did not confirm any influence of lycopene on mental health. Further RCTs are needed to verify the influence of lycopene provided within supplements, functional foods, and regular food products on various mental health problems in diverse populations.