Increased Intake of Vegetables, But Not Fruit, Reduces Risk for Hepatocellular Carcinoma: A Meta-analysis

BACKGROUND & AIMS: The anti-cancer effects of vegetables and fruit have been investigated extensively, but the association between vegetable and fruit consumption and risk of hepatocellular carcinoma (HCC) has not been quantified. We performed a meta-analysis of observational studies to clarify the association. METHODS: We identified eligible studies, published from 1956 through May 31, 2014, by searching PubMed, Web of Science, and EMBASE. Random-effects models were used to calculate summary relative risks (RRs) and dose-response analyses were conducted to quantify associations. Heterogeneity among studies was evaluated using Cochran's Q and I-2 statistics. RESULTS: A total of 19 studies involving 1,290,045 participants and 3912 cases of HCC were included in the meta-analysis. The summary RR for HCC was 0.72 for individuals with high intake vs low intake of vegetables (95% confidence interval [CI]: 0.63-0.83) and 0.92 with a daily increase in vegetable intake (100 g/d) (95% CI: 0.88-0.95). Subgroup analyses showed that this inverse association did not change regardless of history of hepatitis, alcohol drinking, smoking, or energy intake. The summary RR for HCC among individuals with high vs low intake of fruit was 0.93 (95% CI: 0.80-1.09), and 0.99 with a daily increase in fruit intake (100 g/d) (95% CI: 0.94-1.05). CONCLUSIONS: Based on a meta-analysis, increased intake of vegetables, but not fruit, is associated with lower risk for HCC. The risk of HCC decreases by 8% for every 100 g/d increase in vegetable intake. The findings should be confirmed by future studies with validated questionnaires and strict control of confounders.