Dietary intake of tomato and lycopene, blood levels of lycopene, and risk of total and specific cancers in adults: a systematic review and dose-response meta-analysis of prospective cohort studies

Abstract

Background: The association between tomato/lycopene intake and blood levels of lycopene with the risk of specific cancers were assessed in previous meta-analyses; however, no study evaluated the risk of overall cancer incidence/mortality. Therefore, the present systematic review and dose-response meta-analysis aimed to summarize available findings from prospective studies to examine the association between tomato/lycopene intake and lycopene levels with the risk of total and specific cancers and cancer-related mortality. Methods: A comprehensive literature search was done using Scopus, PubMed, ISI Web of Science, and Google Scholar until July 2023. Results: In total, 121 prospective studies were included in the systematic review and 119 in the meta-analysis. During the follow-up period of 2-32 years, a total of 108,574 cancer cases and 10,375 deaths occurred. High intakes and high levels of lycopene compared to low amounts were, respectively, associated with 5 (Pooled RR: 0.95, 95 CI: 0.92-0.98, I-2 = 26.4, p = 0.002) and 11 (Pooled RR: 0.89, 95 CI: 0.84-0.95, I-2 = 15.0, p < 0.001) reduction in overall cancer risk. Also, each 10 mu g/dL increase in blood levels of lycopene was associated with a 5 lower risk of overall cancer. Moreover, we found a linear inverse association between dietary lycopene intake and prostate cancer risk (Pooled RR 0.99, 95 CI 0.97-1.00, I-2 = 0, p = 0.045). Regarding cancer mortality, negative relationships were found with total tomato intake (Pooled RR: 0.89, 95 CI: 0.85-0.93, I-2 = 65.7, p < 0.001), lycopene intake (Pooled RR: 0.84, 95 CI: 0.81-0.86, I-2 = 86.5, p < 0.001) and lycopene levels (Pooled RR 0.76, 95 CI: 0.60-0.98, I-2 = 70.9, p = 0.031). Also, an inverse association was observed between blood lycopene levels and lung cancer mortality (Pooled RR: 0.65, 95 CI: 0.45-0.94, I-2 = 0, p = 0.022). Conclusion: Our findings show that dietary intake and blood levels of lycopene are associated with a lower risk of cancer and death due to cancer.