Mitsuru Kimira

Distribution and Major Sources of Flavonoid Intakes in the Middle-Aged Japanese Women

We estimated the intake of individual flavonoids in a cross sectional study and clarified the major sources contributing to the flavonoid levels in the middle-aged Japanese women by a 24-h weighed dietary record study. The subjects included in the study were 516 free-living women. Each subject completed a 24-h weighed dietary record and received a health check-up. We used the Functional Food Factor database for estimating the intake of 5 major flavonoid intakes, i.e. flavan-3-ols, isoflavones, flavonols, flavanones and flavones. The mean intake of flavan-3-ols, isoflavones, flavonols, flavanones and flavones was 1277, 216, 58, 31 and 15 µmol/d, respectively. The richest source of flavan-3-ols was green tea. The 3 major food sources of isoflavone were the processed soy foods and those of flavonol were the onion, moroheiya (nalta jute) and Japanese radish leaves. Grapefruit and citrus fruit juices were the major sources of flavanones, and tsurumurasaki (malabar spinach), green pepper and grapefruit were the main sources of flavone. Furthermore, analysis of sub-samples from middle-aged Japanese women indicated that there may be an association between flavonoid intake and the levels of oxidized LDL, which might be related to the incidence of cardiovascular diseases.

Effects of human diets of two different Japanese populations on cancer incidence in rat hepatic drug-metabolizing and antioxidant enzyme systems

Hepatic enzyme systems of drug metabolism and antioxidation were investigated in rats fed the complete human diets consumed in the two Japanese prefectures, Akita and Okinawa, where the incidence of cancers was quite different: Okinawa had the lowest and Akita the highest age-adjusted mortality rate. In rats fed the human diet consumed in Okinawa, hepatic glutathione S-transferase activity was higher and lipid peroxide content was lower than in rats fed the diet consumed in Akita. These data might indicate that the number and/or quantity of the dietary components attributed to the detoxification of carcinogens and the scavenging reactive carcinogen species was much higher in the foods consumed in the population having lower cancer mortality rate.

Diet and Cancer: Epidemiological Approaches

Dietary habits are the most important factor in both development and prevention of carcinogenesis. Geographical differences in cancer incidences are mostly attributable to country-specific lifestyles. In Japan, time trends of cancer mortality rates have shown decreasing stomach and uterine cancer rates, and increasing incidences of lung, colon, and breast cancer. These changes may have been caused by changes in the Japanese lifestyle after World War II. Cancer incidences in hormone-related organs, such as of the breast, ovaries, and prostate in Japan are lower than those in Caucasians. The intake of soybeans is considered preventive for these cancers. This protective effect is postulated to be due to the activity of phytoestrogens such as daidzein and genistein. The composition of bacterial flora is thought to play an important role in the absorption and metabolism of phytoestrogens. Geographically, Japan is a long country from north to south in which cancer incidence shows considerable variation. We are conducting a population-based prospective study in 11 health center districts (Koseisho Multipurpose Cohort) to understand the relationship between dietary, lifestyle, and other environmental factors and the occurrence of chronic diseases. The study design has already been introduced. Various constituents of foods are discussed in relation to cancer development and prevention. The usefulness of biomarkers in prospective studies is also discussed.