Evidence that diet is associated with breast cancer risk is inconsistent. Most of the studies have focused on risks associated with specific foods and nutrients, rather than overall diet. In this study, we aimed to evaluate the association between dietary patterns and breast cancer risk in Japanese women. A total of 49 552 Japanese women were followed-up from 1995 to 1998 (5-year follow-up survey) until the end of 2012 for an average of 14·6 years. During 725 534 person-years of follow-up, 718 cases of breast cancer were identified. We identified three dietary patterns (prudent, westernised and traditional Japanese). The westernised dietary pattern was associated with a 32 % increase in breast cancer risk (hazard ratios (HR) 1·32; 95 % CI 1·03, 1·70; Ptrend=0·04). In particular, subjects with extreme intake of the westernised diet (quintile (Q) Q5_5th) had an 83 % increase in risk of breast cancer in contrast to those in the lowest Q1 (HR 1·83; 95 % CI 1·25, 2·68; Ptrend=0·01). In analyses stratified by menopausal status, postmenopausal subjects in the highest quintile of the westernised dietary pattern had a 29 % increased risk of breast cancer (HR 1·29; 95 % CI 0·99, 1·76; Ptrend=0·04). With regard to hormone receptor status, the westernised dietary pattern was associated with an increased risk of oestrogen receptor-positive/progesterone receptor-positivetumours (HR 2·49; 95 % CI 1·40, 4·43; Ptrend<0·01). The other dietary patterns were not associated with the risk of breast cancer in Japanese women. A westernised dietary pattern is associated with an increased risk of breast cancer in Japanese women.

Evidence has shown that both C-reactive protein (CRP) and serum amyloid component A (SAA) are increased in individuals with gastritis and stomach cancer. Controlling the level of these biomarkers by inhibiting the gastric infection with high doses of ascorbic acid may reduce the risk of carcinogenesis. A population-based double-blind randomised controlled trial in a Japanese population with atrophic gastritis in an area of high stomach cancer incidence was conducted between 1995 and 2000. Daily doses of 50 or 500 mg vitamin C were given, and 120 and 124 participants completed the 5-year study, respectively. Although serum ascorbic acid was higher in the high-dosage group (1·73 (sd 0·46) μg/l) than in the low-dosage group (1·49 (sd 0·29) μg/l, P< 0·001), at the end of the study, no significant difference was observed for CRP between the low- and high-dosage groups (0·39 (95 % CI 0·04, 4·19) mg/l and 0·38 (95 % CI 0·03, 4·31) mg/l, respectively; P= 0·63) or for SAA between the low- and high-dosage groups (3·94 (95 % CI 1·04, 14·84) μg/ml and 3·85 (95 % CI 0·99, 14·92) μg/ml, respectively; P= 0·61). Vitamin C supplementation may not have a strong effect on reducing infections in individuals with atrophic gastritis.

Antioxidant vitamins have been reported to be associated with an improvement in blood lipid profiles, but results are not consistent. The present study was designed to determine whether long-term vitamin C supplementation could alter serum lipid concentrations in subjects who completed a 5-year population-based double-blind intervention trial. A total of 439 Japanese subjects with atrophic gastritis initially participated in the trial using vitamin C and β-carotene to prevent gastric cancer. Before and upon early termination of β-carotene supplementation, 134 subjects dropped out of the trial; finally, 161 subjects assigned to the high-dose group (500 mg vitamin C/d) and 144 subjects assigned to the low-dose group (50 mg vitamin C/d) were studied. No favourable effect of vitamin C supplementation on serum concentrations of total cholesterol, HDL- and LDL-cholesterol, and triacylglycerol was observed, although high-dose vitamin C supplementation increased serum vitamin C concentrations substantially. Among women, the mean change in serum triacylglycerol decreased (−0·12 mmol/l, 95 % CI −0·32, 0·09) in the high-dose group, but increased (+0·12 mmol/l, 95 % CI 0·03, 0·22) in the low-dose group. In addition, the mean change in serum triacylglycerol among women with hypertriacylglycerolaemia was statistically significant (−1·21, 95 % CI −2·38, −0·05) after high-dose vitamin C supplementation. The 5-year vitamin C supplementation had no markedly favourable effects on the serum lipid and lipoprotein profile. However, our present results do not preclude the possibility that vitamin C supplementation may decrease triacylglycerol concentrations among women with hypertriacylglycerolaemia.