Junko Ishihara

Intake of Fish and n3 Fatty Acids and Risk of Coronary Heart Disease Among Japanese The Japan Public Health Center-Based (JPHC) Study Cohort I

Background— Once- or twice-weekly consumption of fish (or a small amount of fish intake) reduces the risk of coronary heart disease and sudden cardiac death in Western countries. It is uncertain whether a high frequency or large amount of fish intake, as is the case in Japan, further reduces the risk. Methods and Results— To examine an association between high intake of fish and n3 polyunsaturated fatty acids and the risk of coronary heart disease, a total of 41 578 Japanese men and women aged 40 to 59 years who were free of prior diagnosis of cardiovascular disease and cancer and who completed a food frequency questionnaire were followed up from 1990–1992 to 2001. After 477 325 person-years of follow-up, 258 incident cases of coronary heart disease (198 definite and 23 probable myocardial infarctions and 37 sudden cardiac deaths) were documented, comprising 196 nonfatal and 62 fatal coronary events. The multivariable hazard ratios (HRs) and 95% confidence intervals in the highest (8 times per week, or median intake=180 g/d) versus lowest (once a week, or median intake=23 g/d) quintiles of fish intake were 0.63 (0.38 to 1.04) for total coronary heart disease, 0.44 (0.24 to 0.81) for definite myocardial infarction, and 1.14 (0.36 to 3.63) for sudden cardiac death. The reduced risk was primarily observed for nonfatal coronary events (HR=0.43 [0.23 to 0.81]) but not for fatal coronary events (HR=1.08 [0.42 to 2.76]). Strong inverse associations existed between dietary intake of n3 fatty acids and risk of definite myocardial infarction (HR=0.35 [0.18 to 0.66]) and nonfatal coronary events (HR=0.33 [0.17 to 0.63]). Conclusions— Compared with a modest fish intake of once a week or ≈20 g/d, a higher intake was associated with substantially reduced risk of coronary heart disease, primarily nonfatal cardiac events, among middle-aged persons.

Association of dietary intake of soy, beans, and isoflavones with risk of cerebral and myocardial infarctions in Japanese populations: the Japan Public Health Center-based (JPHC) study cohort I.

Background— Soy and isoflavones have been proposed to reduce the risk of cardiovascular risk factors, but their potential as preventatives for cardiovascular disease remains uncertain. We investigated the association of soy and isoflavone intake with risk of cerebral and myocardial infarctions (CI and MI). Methods and Results— To examine the association of soy and isoflavone intake with the risk of CI and MI, we studied 40 462 Japanese (40 to 59 years old, without cardiovascular disease or cancer at baseline). They completed a food-frequency questionnaire (1990–1992) and received follow-up to 2002. After 503 998 person-years of follow-up, we documented incidence of CI (n=587) and MI (n=308) and of mortality for CI and MI combined (n=232). For women, the multivariable hazard ratios and 95% confidence limits for soy intake ≥5 times per week versus 0 to 2 times per week were 0.64 (0.43 to 0.95) for risk of CI, 0.55 (0.26 to 1.09) for risk of MI, and 0.31 (0.13 to 0.74) for cardiovascular disease mortality. Similar but weaker inverse associations were observed between intake of miso soup and beans and risk of cardiovascular disease mortality. The multivariable hazard ratios for the highest versus the lowest quintiles of isoflavones in women were 0.35 (0.21 to 0.59) for CI, 0.37 (0.14 to 0.98) for MI, and 0.87 (0.29 to 2.52) for cardiovascular disease mortality. An inverse association between isoflavone intake and risk of CI and MI was observed primarily among postmenopausal women. No significant association of dietary intake of soy, miso soup, and beans and isoflavones with CI or MI was present in men. Conclusions— High isoflavone intake was associated with reduced risk of CI and MI in Japanese women. The risk reduction was pronounced for postmenopausal women.

Quantification of the co-mutagenic β-carbolines, norharman and harman, in cigarette smoke condensates and cooked foods

Co-mutagenic beta-carbolines, such as norharman and harman, were quantified in mainstream and sidestream smoke condensates of six Japanese brands of cigarettes, and also in 13 kinds of cooked foods, using a combination of blue cotton treatment and HPLC. Norharman and harman were detected in all the cigarette smoke condensate samples. Their levels in the mainstream smoke case were 900-4240 ng per cigarette for norharman, and 360-2240 ng for harman, and in sidestream smoke, 4130-8990 ng for norharman and 2100-3000 ng for harman. These beta-carbolines were also found to be present in all the cooked food samples, at levels of 2.39-795 ng for norharman and 0.62-377 ng for harman per gram of cooked food. The observed concentrations are much higher than those found for mutagenic and carcinogenic heterocyclic amines (HCAs), suggesting that humans are exposed to norharman and harman in daily life to a larger extent than to HCAs.

Dietary Calcium Intake and Risks of Stroke, Its Subtypes, and Coronary Heart Disease in Japanese: The JPHC Study Cohort I

Background and Purpose— Although it has been hypothesized that a high intake of dietary calcium may reduce the risk of cardiovascular disease (CVD), no prospective studies have been conducted to examine the specific association between calcium intake and incidence of stroke or coronary heart disease among Japanese with a low average calcium intake. Methods— To investigate the association between calcium intake and risk of CVD, a total of 41 526 Japanese men and women age 40 to 59 years without a history of CVD or cancer and who had completed a food consumption frequency questionnaire were enrolled in this study. The subjects were followed up from 1990 to 1992 to 2003, and after 533 692 person-years of follow-up, 1321 incident cases of stroke (664 ischemic, 425 intraparenchymal hemorrhage, and 217 subarachnoid hemorrhage) and 322 of coronary heart disease were documented. Results— Total calcium intake showed an inverse association with the risk of total stroke; the multivariable hazard ratio and 95% CIs for the highest versus the lowest quintile were 0.70 (95% CI, 0.56 to 0.88; P for trend=0.02). Dairy calcium intake was inversely associated with risks of total and ischemic stroke with respective multivariable hazard ratios (95% CIs) of 0.69 (0.56 to 0.85; P for trend=0.007) and 0.69 (0.52 to 0.93; P for trend=0.05). Dietary calcium intake was not significantly associated with risk of coronary heart disease. Conclusions— Dietary calcium intake, especially calcium from dairy products, was found to be associated with a reduced incidence of stroke among middle-aged Japanese.

The Impact of Green Tea and Coffee Consumption on the Reduced Risk of Stroke Incidence in Japanese Population The Japan Public Health Center-Based Study Cohort

Background and Purpose— Few prospective studies have examined the impact of both green tea and coffee consumption on strokes. We investigated the association of the combination of those consumption with stroke incidence in a general population. Methods— We studied 82 369 Japanese (aged 45–74 years; without cardiovascular disease [CVD] or cancer in 1995 and 1998 for Cohort I and II, respectively) who received 13 years of mean follow-up through the end of 2007. Green tea and coffee consumption was assessed by self-administered food frequency questionnaire at baseline. Results— In the 1 066 718 person-years of follow-up, we documented the incidence of strokes (n=3425) and coronary heart disease (n=910). Compared with seldom drinking green tea, the multivariable-adjusted hazard ratios (95% confidence intervals) of all strokes were 0.86 (0.78–0.95) and 0.80 (0.73–0.89) in green tea 2 to 3 and ≥4 cups/d, respectively. Higher green tea consumption was associated with inverse risks of CVD and strokes subtypes. Compared with seldom drinking coffee, the multivariable-adjusted hazard ratios (95% confidence intervals) of all strokes were 0.89 (0.80–0.99), 0.80 (0.72–0.90), and 0.81 (0.72–0.91) for coffee 3 to 6 times/week and 1 and ≥2 times/day, respectively. Coffee consumption was associated with an inverse risk of CVD and cerebral infarction. Higher green tea or coffee consumption reduced the risks of CVD and stroke subtypes (especially in intracerebral hemorrhage, P for interaction between green tea and coffee=0.04). None of the significant association was observed in coronary heart disease. Conclusions— Higher green tea and coffee consumption were inversely associated with risk of CVD and stroke in general population.

Folate, Vitamin B6, Vitamin B12, and Vitamin B2 Intake, Genetic Polymorphisms of Related Enzymes, and Risk of Colorectal Cancer in a Hospital-Based Case-Control Study in Japan

Abstract: We conducted a case-control study to investigate the association of nutrient intake involved in the one-carbon pathway of folate for DNA methylation and DNA synthesis and the related enzyme genetic polymorphisms with colorectal cancer. Cases were 107 patients newly diagnosed with colorectal cancer. Controls were 224 subjects matched with cases by sex, age, and residential area. Nutrient intake was assessed by a self-administered, semiquantitative food-frequency questionnaire. Four genetic polymorphisms—MTHFR C677T and A1298C, MTRR A66G, and ALDH2 Glu487Lys—were determined using blood samples. Odds ratios were calculated using conditional logistic regression analysis adjusted for smoking, alcohol consumption, body mass index, and dietary fiber intake. Although folate intake was inversely associated with colorectal cancer, this association was attenuated after further controlling for dietary fiber intake. Neither vitamin B6, vitamin B12, nor vitamin B2, nor any genetic polymorphism was significantly associated with colorectal cancer. MTRR polymorphism interacted with the association of folate (P for interaction = 0.04) or vitamin (P for interaction = 0.02) with colorectal cancer, although the other polymorphisms did not interact with any nutrient intake. In conclusion, the study did not support the existing hypothesis of gene-nutrient interaction in colorectal carcinogenesis.

Consumption of sodium and salted foods in relation to cancer and cardiovascular disease: the Japan Public Health Center-based Prospective Study.

BACKGROUND Although the influence of salt, per se, on the risk of cancer or cardiovascular disease (CVD) might differ from that of salt-preserved foods, few studies have simultaneously examined the effects of sodium and salted foods on the risk of either cancer or CVD. OBJECTIVE We simultaneously examined associations between sodium and salted food consumption and the risk of cancer and CVD. DESIGN During 1995-1998, a validated food-frequency questionnaire was administered to 77,500 men and women aged 45-74 y. During up to 598,763 person-years of follow-up until the end of 2004, 4476 cases of cancer and 2066 cases of CVD were identified. RESULTS Higher consumption of sodium was associated with a higher risk of CVD but not with the risk of total cancer: multivariate hazard ratios for the highest compared with lowest quintiles of intake were 1.19 (95% CI: 1.01, 1.40; P for trend: 0.06) for CVD and 1.04 (95% CI: 0.93, 1.16; P for trend: 0.63) for total cancer. Higher consumption of salted fish roe was associated with higher risk of total cancer, and higher consumption of cooking and table salt was associated with higher risk of CVD. Similar results were seen for the risk of gastric or colorectal cancer and stroke. CONCLUSIONS Sodium intake as a whole salt equivalent may not increase the risk of cancer but may increase that of CVD. In contrast, salted food intake may increase the risk of cancer. Our findings support the notion that sodium and salted foods have differential influences on the development of cancer and CVD.

Dietary calcium, vitamin D, and the risk of colorectal cancer

BACKGROUND Calcium and vitamin D have a potential protective effect against colorectal cancer. OBJECTIVE We investigated the association of dietary intake of calcium and vitamin D with the risk of colorectal cancer in a large prospective cohort study of middle-aged Japanese men and women. DESIGN A total of 74 639 subjects (35 194 men and 39 445 women) who participated in the Japan Public Health Center-based Prospective Study were followed from 1995-1999 to the end of 2004, during which time 761 cases of colorectal cancer (464 men, 297 women) were newly identified. Dietary intake of nutrients was calculated with the use of a 138-item self-administered food-frequency questionnaire. RESULTS After adjusting for potential confounding factors, the multivariate hazard ratio in the highest quintile of dietary calcium intake compared with the lowest was 0.71 (95% CI: 0.52, 0.98) among men. The association appeared to decrease considerably among subjects in the second quintile without a clear further dose-response relation (P for trend: 0.09). No association was seen among women. No statistically significant association with dietary vitamin D intake was seen in either men or women, although men in the highest dietary intake group of both nutrients had a lower risk than did men in the lowest group. CONCLUSIONS These findings indicate a potential decrease in the risk of colorectal cancer with higher dietary intake of calcium among middle-aged Japanese men, who have a relatively low dietary intake of calcium. Although vitamin D and colorectal cancer risk were not associated, potential effect modification between calcium and vitamin D on the risk of colorectal cancer was indicated.

Impact of the revision of a nutrient database on the validity of a self-administered food frequency questionnaire (FFQ).

BACKGROUND Revision of the national nutrient database in 2000 had a strong impact on the absolute level of estimated nutrient intake in dietary assessments. However, whether it influenced the ranking of individuals by estimated intake, a more important function in epidemiologic studies, has not been investigated. Here, we investigated the effect of this revision of the nutrient database on the validity of a food frequency questionnaire (FFQ) used to estimate nutrient intake in the Japan Public Health Center-based prospective Study (JPHC Study). METHODS Subjects were a subsample of the JPHC Study who volunteered to participate in the validation study of the FFQ. Validity of the FFQ was evaluated by reference to the 28-day weighed dietary records as a gold standard. Nutrient intake according to the FFQ was recalculated using the revised database, and the results were compared to those using the previous database. Spearman’s rank correlation coefficients (CCs) between intakes estimated by the FFQ and dietary records were computed using the revised database, and were compared to CCs computed using the previous database. RESULTS For most of the nutrients, mean intake increased or decreased significantly using the revised database. However, no notable change was seen for the CC between estimated intake according to dietary records and FFQ when the revised database was used for calculation. Differences in the point estimates of the CCs ranged from -0.14 to 0.15. Likewise, CCs between biomarkers and estimated intake according to FFQ were similar for the two databases. CONCLUSION Despite changes in intake levels for many nutrients, the validity of our FFQ using rank correlation by nutrient intake was not influenced by revision of the nutrient database in Japan.

Reproducibility and Validity of Dietary Patterns Assessed by a Food Frequency Questionnaire Used in the 5-Year Follow-Up Survey of the Japan Public Health Center-Based Prospective Study

Background Analysis of dietary pattern is increasingly popular in nutritional epidemiology. However, few studies have examined the validity and reproducibility of dietary patterns. We assessed the reproducibility and validity of dietary patterns identified by a food frequency questionnaire (FFQ) used in the 5-year follow-up survey of the Japan Public Health Center-Based Prospective Study (JPHC Study). Methods The participants were a subsample (244 men and 254 women) from the JPHC Study. Principal component analysis was used to identify dietary patterns from 28- or 14-day dietary records and 2 FFQs. To assess reproducibility and validity, we calculated Spearman correlation coefficients between dietary pattern scores derived from FFQs separated by a 1-year interval, and between dietary pattern scores derived from dietary records and those derived from a FFQ completed after the dietary records, respectively. Results We identified 3 Japanese dietary patterns from the dietary records and 2 FFQs: prudent, westernized, and traditional. Regarding reproducibility, Spearman correlation coefficients between the 2 FFQs ranged from 0.55 for the westernized Japanese pattern in men and the prudent Japanese pattern in women to 0.77 for the traditional Japanese pattern in men. Regarding validity, the corresponding values between dietary records and the FFQ ranged from 0.32 for the westernized Japanese pattern in men to 0.63 for the traditional Japanese pattern in women. Conclusions Acceptable reproducibility and validity was shown by the 3 dietary patterns identified by principal component analysis based on the FFQ used in the 5-year follow-up survey of the JPHC Study.