Dietary intake and blood concentrations of vitamin C and total cancer: dose-response analyses. (A) Dietary vitamin C and total cancer: linear dose-response analysis. The summary RR per 100 mg/d was 0.93 (95% CI: 0.87, 0.99, I2 = 46%, Pheterogeneity = 0.08, n = 8). (B) Vitamin C in blood and total cancer: linear dose-response analysis. The summary RR per 50 µmol/L was 0.74 (95% CI: 0.66, 0.82, I2 = 0%, Pheterogeneity = 0.49, n = 5). (C) Dietary vitamin C and total cancer: nonlinear dose-response analysis. There was evidence of nonlinearity between dietary vitamin C and total cancer (Pnonlinearity = 0.007). (D) Vitamin C in blood and total cancer: nonlinear dose-response analysis. There was evidence of nonlinearity for vitamin C in blood and total cancer (Pnonlinearity = 0.006). Summary RRs and 95% CIs were calculated with the use of random-effects models, and the nonlinear dose-response analyses were conducted with the use of restricted cubic splines. SMHS, Shanghai Men's Health Study; SWHS, Shanghai Women's Health Study.