Chisato Nagata

Estimated Asian adult soy protein and isoflavone intakes.

Abstract: There is substantial interest in the possible anticancer effects of soy foods. In part, this is because of the historically low incidence rates of breast and prostate cancer in Asia. Of the several putative soybean chemopreventive agents, isoflavones have received the most attention. Awareness of this research has led increasing numbers of consumers to use soy foods, isoflavone-fortified foods, and isoflavone supplements. Therefore, there is a need for guidance regarding appropriate isoflavone intake levels. To this end, this article analyzed soy protein (as a surrogate for isoflavones) and isoflavone intake of the major soy food-consuming countries using individual dietary surveys for the bulk of the information. In total, 24 surveys from 4 countries that met the inclusion criteria were identified: Japan (n = 11), China (n = 7), Hong Kong (n = 4), and Singapore (n = 2). The results indicate that older Japanese adults consume approximately 6-11 g of soy protein and 25-50 mg of isoflavones (expressed as aglycone equivalents) per day. Intake in Hong Kong and Singapore is lower than in Japan, whereas significant regional intake differences exist for China. Evidence suggests that ≤10% of the Asian population consumes as much as 25 g of soy protein or 100 mg of isoflavones per day. The applicability of these findings for making soy intake recommendations for non-Asians is discussed.

Sodium Intake and Risk of Death From Stroke in Japanese Men and Women

Background and Purpose— Despite the evidence for a positive association of dietary salt and blood pressure, the few prospective studies that have assessed the association between dietary salt and stroke have reported inconsistent results. The purpose of this study was to examine the relation between sodium intake and death from stroke in a population-based cohort of Japanese men and women. Methods— In 1992, usual diet including sodium intake was determined in 13 355 men and 15 724 women in Takayama City, Gifu, with the use of a validated food frequency questionnaire. Results— There were 269 stroke deaths (137 men and 132 women) between baseline and 1999. In men, the highest compared with the lowest tertile of sodium intake was significantly positively associated with death from total stroke after controlling for covariates (hazard ratio [HR]), 2.33; 95% CI, 1.23 to 4.45). Significantly positive associations were also observed between sodium intake and death from ischemic stroke (HR, 3.22; 95% CI, 1.22 to 8.53) as well as death from intracerebral hemorrhage (HR, 3.85; 95% CI, 1.16 to 12.7). A positive association between sodium intake and death from stroke in women was suggested, although the associations for total stroke and ischemic stroke were of borderline significance (HR, 1.70; 95% CI, 0.96 to 3.02 and HR, 2.10; 95% CI, 0.96 to 4.62, respectively). Conclusions— These prospective data support the hypothesis that dietary salt increases the risk of death from stroke.

Tobacco smoking and lung cancer risk: an evaluation based on a systematic review of epidemiological evidence among the Japanese population.

BACKGROUND Although tobacco smoking is the best established risk factor for lung cancer, the association is not as strong among Japanese as among Western populations. It would be of value, therefore, to quantify that association in Japan based on a systematic review of epidemiological evidence for the primary prevention of lung cancer. METHODS Original data were obtained from MEDLINE searches using PubMed, supplemented with manual searches. The evaluation of associations was based on the strength of evidence and the magnitude of the association, together with biological plausibility as previously evaluated by the International Agency for Research on Cancer. A meta-analysis was also conducted to estimate the summary measure of those associations. RESULTS A total of 8 cohort studies and 14 case-control studies were identified, almost all of which consistently showed a strong association of current smoking with the risk of lung cancer. The summary relative risk for current smokers versus never smokers was estimated as 4.39 (95% confidence interval 3.92-4.92) for men and 2.79 (95% confidence interval 2.44-3.20) for women. Cohort studies and case-control studies gave reasonably consistent summary measures. The summary relative risks were 11.7 and 2.30 for squamous cell carcinoma and adenocarcinoma, respectively, in men, and were 11.3 and 1.37 correspondingly in women. CONCLUSION There is convincing evidence that tobacco smoking strongly increases the risk of lung cancer in the Japanese population, with the relative risk for current smokers compared with never smokers measuring around 4.4 for men and 2.8 for women.

Association of coffee, green tea, and caffeine intakes with serum concentrations of estradiol and sex hormone‐binding globulin in premenopausal Japanese women

Caffeine intake has been proposed to influence breast cancer risk. Its effect may be mediated by hormonal changes. The relationships between caffeine-containing beverages (coffee, green tea, black tea, oolong tea, and cola) and serum concentrations of estradiol and sex hormone-binding globulin were evaluated in 50 premenopausal Japanese women. Intakes of caffeine and caffeine-containing beverages were assessed by a semiquantitative food-frequency questionnaire. Blood samples were obtained from each woman on Days 11 and 22 of her menstrual cycle. High intakes of caffeinated coffee, green tea, and total caffeine were commonly correlated with increasing sex hormone-binding globulin on Days 11 and 22 of the cycle after controlling for potential confounders [Spearman correlation coefficients (r) ranged from 0.23 to 0.31]. Green tea but not caffeinated coffee intake was inversely correlated with estradiol on Day 11 of the cycle (r = -0.32, p = 0.04). Although the effect of caffeine cannot be distinguished from effects of coffee and green tea, consumption of caffeine-containing beverages appeared to favorably alter hormone levels associated with the risk of developing breast cancer.

Decreased serum estradiol concentration associated with high dietary intake of soy products in premenopausal Japanese women

We examined the cross-sectional relationship of soy product intake to serum concentrations of estradiol (E2) and sex hormone-binding globulin (SHBG) in 50 healthy premenopausal Japanese women. Intakes of soy products and various nutrients were estimated through a semiquantitative food-frequency questionnaire. Blood samples were drawn from each subject on Days 11 and 22 of her menstrual cycle. The intake of soy products was inversely correlated with E2 on Days 11 and 22 of the cycle after controlling for age, body mass index, cycle length, and intakes of total energy, fat, and crude fiber (r = -0.23, p = 0.08 and r = -0.32, p = 0.04, respectively). No significant correlation was observed between soy product intake and SHBG. There was a tendency for the intake of individual soy foods such as tofu and miso to be inversely correlated with E2 on Days 11 and 22 of the menstrual cycle. Miso intake was inversely significantly correlated with SHBG on Day 22 of the cycle (r = -0.36, p = 0.02). If the observed association is causal, our results suggest that the consumption of soy products lowers the risk of developing breast cancer risk modifying estrogen metabolism.

Tobacco Smoking and Gastric Cancer Risk: An Evaluation Based on a Systematic Review of Epidemiologic Evidence among the Japanese Population

OBJECTIVE The association between fish consumption and colorectal cancer risk remains inconclusive. The present study systematically reviewed and meta-analyzed epidemiologic data on the association between fish consumption and colorectal cancer risk among Japanese. METHODS Original data were obtained from MEDLINE searched using PubMed or from searches of the Ichushi database, complemented with manual searches. The associations were evaluated based on the strength of evidence, the magnitude of association and biologic plausibility. Meta-analysis was conducted according to the study design. RESULTS Five cohort studies and 12 case-control studies were identified. Fish consumption was not significantly associated with colorectal, colon or rectal cancer risks. One cohort study showed a weak positive association with colorectal cancer, and another showed a weak inverse association with colon cancer in men and a moderate and weak inverse association with colon and rectal cancers in women. As regards case-control studies, four studies reported a weak inverse association, whereas one showed a weak positive association with colon cancer. Regarding rectal cancer, four case-control studies showed a weak inverse association, but two reported a weak-to-moderate positive association. The pooled relative risk/odds ratio (95% confidence interval) of colorectal cancer for the highest versus lowest category of fish consumption was 1.03 (0.89-1.18) and 0.84 (0.75-0.94) for cohort and case-control studies, respectively. CONCLUSIONS There was insufficient evidence to support an association between fish consumption and the risk of colorectal cancer among Japanese.

Height, weight, and alcohol consumption in relation to the risk of colorectal cancer in Japan: a prospective study

Colorectal cancer incidence in relation to body size, smoking, and alcohol consumption was studied in a cohort of 29 051 city residents of Japan. In 1992, each participant completed a self-administered questionnaire on sociodemographic characteristics, drinking, cigarette smoking, diet, exercise, and reproductive and medical histories. The response rate was 92%. From 1993 to 2000, 161 men and 134 women were diagnosed with colorectal cancer at two major hospitals in the city. Relative risks and 95% confidence intervals were calculated by using Cox proportional hazard models. A positive relation between height and colorectal cancer was seen in both sexes, controlling for age, body mass index (BMI), smoking and drinking habits, and years of education. The findings were statistically significant only for men (relative risk 2.13 for the tallest compared with the shortest height tertile; 95% confidence interval=1.26–3.58). Body mass index was also associated positively with colon cancer risk for men, whereas the pattern for women was not clear. There was a positive association between pack-years of cigarette smoking and the risk of rectal cancer in men. A positive dose–response relation between alcohol consumption and colon cancer risk was observed for men and women.

Consumption of coffee, green tea, oolong tea, black tea, chocolate snacks and the caffeine content in relation to risk of diabetes in Japanese men and women

Although the inverse association between coffee consumption and risk of diabetes has been reported numerous times, the role of caffeine intake in this association has remained unclear. We evaluated the consumption of coffee and other beverages and food containing caffeine in relation to the incidence of diabetes. The study participants were 5897 men and 7643 women in a community-based cohort in Takayama, Japan. Consumption of coffee, green tea, oolong tea, black tea and chocolate snacks were measured with a semi-quantitative FFQ in 1992. At the follow-up survey in 2002, the development of diabetes and the time of diagnosis were reported. To assess the association, age, smoking status, BMI, physical activity, education in years, alcohol consumption, total energy intake, fat intake and womens menopausal status were adjusted. Among men who consumed one cup per month to six cups per week and among those who consumed one cup per d or more, the associated hazard ratios were 0.69 (95 % CI 0.50, 0.97) and 0.69 (95 % CI 0.49, 0.98) compared with those who drank little to no coffee, with a P value for trend of 0.32. The hazard ratios for women with the same coffee consumption patterns were 1.08 (95 % CI 0.74, 1.60) and 0.70 (95 % CI 0.44, 1.12), with a P value for trend of 0.03. The association between estimated total caffeine intake and risk of diabetes was insignificant both among men and among women. The results imply that coffee consumption decreased the risk of developing diabetes. The protective effect may exist aside from the influence of caffeine intake.

Association of body mass index, physical activity, and reproductive histories with breast cancer: a case-control study in Gifu, Japan

To further clarify risk factors for breast cancerin Japanese women, a self-administered questionnaire was completedby 157 cases with histologically confirmed breast cancerfrom 1989 to 1993 and by 369 ageand residential area matched controls in Gifu, Japan.Conditional logistic regression model was used to assessthe relations. Multivariate analyses showed that breast cancerrisk decreased with body mass index for premenopausalwomen (RR=0.45; 95% CI=0.22–0.92for BMI ≥ 23 vs. < 21 (kg/m2)),but the risk increased with body mass indexfor postmenopausal women (RR=1.98; 95% CI= 0.86–4.55 for BMI ≥ 24 vs. <21.5 (kg/m2)). The risk increased with a smallnumber of births in pre- and post-menopausal women(1.83; 1.11–2.99 and 6.06; 2.40–15.3 for 1–2 birthsand nulliparity, respectively, vs. ≥ 3 births). Ex-or current smoking increased the risk of breastcancer (2.31; 1.19–4.49). Reduced risk of premenopausal breastcancer was associated with high energy expenditure inphysical activity during teenage, although the trend wasnot statistically significant.

Inverse Association of Soy Product Intake With Serum Androgen and Estrogen Concentrations in Japanese Men

The cross-sectional relationships of soy product intake and serum testosterone, estrone, estradiol, sex hormone-binding globulin, and dihydrotestosterone were examined in 69 Japanese men. Soy product intake was estimated from a semiquantitative food frequency questionnaire. Serum estradiol concentration was significantly inversely correlated with soy product intake (r = -0.32, p = 0.009), and serum estrone concentration was nonsignificantly inversely correlated with soy product intake (r = -0.24, p = 0.05) after controlling for age, body mass index, smoking status, and ethanol intake. Total and free testosterone concentrations were inversely correlated with soy product intake after controlling for the covariates, but these correlations were of borderline significance (r = -0.25, p = 0.05 and r = -0.25, p = 0.06, respectively). Similar correlations were observed for these hormones with isoflavone intake from soy products. The data suggest that soy product intake may be associated with the endogenous hormone levels in Japanese men.