Effect of tomato, lycopene and related products on blood pressure: A systematic review and network meta-analysis

Abstract

Background: A number of randomized controlled trials (RCTs) have been conducted to evaluate the hypotensive effects of tomato, lycopene, and related products. However, the findings were conflicting, partly due to differences in the types of products investigated. Therefore, this study aimed to assess and compare the hypotensive effects of different tomato-related preparations through a network meta-analysis based on randomized controlled trials. Study design: A systematic review and network meta-analysis. Methods: A network meta-analysis based on a systematic review of RCTs comparing the effect of various tomato, lycopene and related products versus placebo on blood pressure in adults was performed. PubMed, EMBASE, SCOPUS, and Clinicaltrial.gov databases were searched up to October 2020 without language restrictions. The primary outcomes were systolic and diastolic blood pressure. Mean differences (MDs) along with 95% confidence intervals (CIs) were estimated and pooled using a random-effects model. Heterogeneity was assessed using the global inconsistency test. Results: A total of 11 studies including six forms of tomato, lycopene and related products met the inclusion criteria. Among these trials, eight (N = 617) and seven trials (N = 501) were included in the analysis of systolic (SBP) and diastolic blood pressure (DBP) outcomes, respectively. The standardized tomato extract (STE) significantly decreased SBP compared to placebo, with a pooled MD (95% CI) of –5.89 (–9.13 to –2.64) mmHg. The effect on DBP was not significant, with a pooled MD (95% CI) of –3.51 (–7.39 to 0.38) mmHg. Subgroup analysis in hypertensive patients showed that STE significantly reduced both SBP and DBP with pooled MDs (95% CIs) of –8.09 (–11.52 to –4.67) and –4.25 (–6.97 to –1.53) mmHg, respectively, compared to placebo. Other forms of tomato, including other dose ranges of standardized tomato extract, tomato-containing diet, lycopene-free preparation, and synthetic lycopene, did not show consistent and significant effects on either SBP or DBP in all analyses. Conclusion: Standardized tomato extract (STE) significantly decreased SBP compared to placebo in a mixed population of healthy volunteers and hypertensive patients. The BP-lowering effect was more pronounced among hypertensive patients. No significant BP effects were seen with other forms of tomato, lycopene and related products in the overall population or any subgroup of the population.