A population-based dietary intervention trial in a high-risk area for stomach cancer and stroke: changes in intakes and related biomarkers

Background Dietary intervention is one of the important fields in cancer and cardiovascular disease prevention. The Hiraka Dietary Intervention Study is a community-based randomized cross-over trial designed to develop an effective dietary modification tool and system in an area with high mortality of stomach cancer and stroke. Methods The subjects were 550 healthy volunteers and were randomized into two groups with tailored dietary education to decrease sodium intake and to increase vitamin C and carotene intakes either in the first year (intervention group) or in the second year (control group). Dietary changes were assessed using a validated self-administered diet history questionnaire, fasting blood samples, and 48-hour urine samples, which were obtained before and after the one year period. Results During the first year, changes differed significantly between the intervention and control group for both dietary sodium intake (−384 and +255 mg/day, intervention and control respectively, p < 0.001) and urinary sodium excretion (−1003 and −84 mg/day, p < 0.001). Although favorable net changes were also observed in dietary carotene (+418 and +220 μg/day, p < 0.05) and vitamin C (+13 and +2 mg/day, p < 0.05), the serum level differences were modest (+13 and −25 mg/L, p = 0.09 for carotene, +0.1 and −0.5 mg/L, p = 0.07 for ascorbic acid). Conclusion The present dietary intervention strategy effectively decreased sodium and increased carotene and vitamin C intakes, although the former was more distinct.