A case‐control study of diet and prostate cancer in Japan: possible protective effect of traditional Japanese diet

Abstract

The age-adjusted incidence of prostate cancer is low in Japan, and it has been suggested that the traditional Japanese diet, which includes many soy products, plays a preventive role against prostate cancer. We performed a case-control study on dietary factors and prostate cancer in order to assess the hypothesis that the traditional Japanese diet reduces the risk of prostate cancer. Four geographical areas (Ibaraki, Fukuoka, Nara, and Hokkaido) of Japan were selected for the survey. Average daily intake of food from 5 years before the diagnosis was measured by means of a semi-quantitative food frequency questionnaire. We studied 140 cases and 140 individually age ( ± ± ± ±5 years)-matched hospital controls for analysis. Estimates of age-adjusted odds ratios (ORs) and linear trends were calculated by conditional logistic regression models with adjustment for cigarette smoking and total energy intake as confounding factors. Consumption of fish, all soybean products, tofu (bean curds), and natto (fermented soybeans) was associated with decreased risk. ORs of the fourth vs. first quartile and 95% confidence intervals (95%CIs) were 0.45 (0.20-1.02) for fish, 0.53 (0.24-1.14) for all soybean products, 0.47 (0.20-1.08) for tofu, and 0.25 (0.05-1.24) for natto. Consumption of fish and natto showed significantly decreasing linear trends for risk (P < < < <0.05). Consumption of meat was significantly associated with increased risk (the OR of the second vs. first quartile was 2.19, 95%CI 1.00-4.81). Consumption of milk, fruits, all vegetables, green-yellow vegetables, and tomatoes showed no association. Our results provide support to the hypothesis that the traditional Japanese diet, which is rich in soybean products and fish, might be protective against prostate cancer. (Cancer Sci 2004; 95: 238-242) he age-standardized incidence of prostate cancer is low in Japan (10.0 per 100,000), being approximately one-tenth of that in the United States.1) Among Japanese immigrant in Hawaii, age-standardized incidence of prostate cancer is approximately ten times that in Japan.2) It is suggested that environmental factors such as dietary habits play a major role in causation of prostate cancer. A number of case-control studies have indicated that high intake of fat, especially saturated fat, increases the risk of prostate cancer.3) In contrast, high intake of isoflavone, which is mainly found in soybeans and soy products, may reduce the risk of prostate cancer. 4,5) The traditional Japanese diet which includes many soy products is richer in isoflavone, 6,7) and contains less fat than the Western diet. However, an epidemiological study of prostate cancer in Kyoto in 1988 8) yielded no evidence that fat or soybeans were associated with the risk of prostate cancer.Recently in Japan, the incidence rate of prostate cancer has been increasing cocomitantly with the westernization of dietary habits. We carried out a case-control study on dietary factors and prostate cancer to assess the hypothesis that the traditional Japanese diet reduc...

No association between green tea and prostate cancer risk in Japanese men: the Ohsaki Cohort Study

“…We found no association between green-tea consumption and prostate cancer incidence among Japanese men, who consume green tea much more frequently than men in Western countries. Our results conflicted with those of a case -control study in China (Jian et al, 2004), but agreed with those of a prospective study in Hawaii and a casecontrol study in Japan showing no association between green-tea consumption and prostate cancer incidence (Severson et al, 1989;Sonoda et al, 2004).…”

“…Although laboratory studies have suggested a protective effect of green-tea polyphenols against development of prostate cancer in animal models (Gupta et al, 1999; Saleem et al, 2003), few epidemiological studies have examined the association. A casecontrol study in China found that green-tea intake was associated with a lower risk of prostate cancer (Jian et al, 2004), whereas a prospective study of Japanese Americans in Hawaii and a casecontrol study in Japan found no such association (Severson et al, 1989;Sonoda et al, 2004). The age-standardised incidence of prostate cancer is low in Japan (12.7 per 100 000), being approximately one-tenth of that in the US (Parkin, 2002).…”

Age-stratified serum levels of isoflavones and proportion of equol producers in Japanese and Korean healthy men

“…[18][19][20] Those studies of the serum equol level revealed two types of men with different metabolic patterns of daidzein to equol; one group is equol producers and the other is equol non-producers whose serum equol was under the detection level (0.5 ng ml À1 ), and the proportion of equol producers among patients with prostate cancer was significantly lower than that among the agematched control group patients. 18 Moreover, the proportion of equol producers was significantly lower among patients with poorly differentiated adenocarcinoma than among those with well or moderately differentiated adenocarcinoma.…”

“…They recorded all items and amounts of food and drink ingested with the interviewer's assistance. 20 The daily intakes of soybean proteins and isoflavones (total isoflavone, genistein aglycones and daidzein aglycones) during the week before blood sampling were calculated from the above-mentioned data by adding the intake of soybean food items in detail and multiplying the gram-portion size by the soybean foods frequency per day. Calculation of the estimated amount of daily intakes of soybean proteins and isoflavones was carried out by using the published database at the Department of Public Health in Sapporo Medical University.…”

Precise Preoperative Localization of Prostate Cancer Employing 12-Core Needle Biopsy with a Tissue-Marking Method for Effective Surgical Strategy

“…This increased incidence could be partly explained by the widely applied prostate-specific antigen (PSA) screening (Sonoda et al 2004). Needle biopsy is the most common diagnostic modality for prostate cancer after serum PSA screening.…”