Nut Consumption and Risk of Cancer: A Meta-analysis of Prospective Studies

Background: Epidemiologic studies have investigated the association between nut intake and risk for multiple cancers. However, current findings are inconsistent and no definite conclusion has been drawn from prospective studies. We therefore conducted this meta-analysis to evaluate the relationship between nut consumption and risk of cancer. Methods: Prospective studies reporting associations between nut intake and risk for all types of cancer were identified by searching Web of Science and PubMed databases up to June 2019. Risk ratios (RR) and 95% confidence intervals (CI) were extracted and then pooled across the studies using a random-effect model. A dose-response analysis was modeled by performing restricted cubic splines when data were available. Results: Thirty-three studies that included more than 50,000 cancer cases were eligible for the analysis. When comparing the highest with the lowest category of nut intake, high consumption of nuts was significantly associated with decreased risk of overall cancer (RR = 0.90; 95% CI, 0.85-0.95). The protective effect of nut consumption was especially apparent against cancers from the digestive system (RR = 0.83; 95% CI, 0.77-0.89). Among different nut classes, significant association was only obtained for intake of tree nuts. We also observed a linear dose-response relationship between nut consumption and cancer: Per 20 g/day increase in nut consumption was related to a 10% (RR = 0.90; 95% CI, 0.82-0.99) decrease in cancer risk. Conclusions: Our analysis demonstrated an inverse association of dietary nut consumption with cancer risk, especially for cancers from the digestive system. Impact: This study highlights the protective effect of nuts against cancer.