Plasma Isoflavone Concentrations Are Not Associated with Gastric Cancer Risk among Japanese Men and Women1,2

Abstract

The incidence of gastric cancer throughout the world is ~2-3 times higher in men than in women. Previous research suggested that isoflavones, which are structurally similar to 17β-estradiol, may prevent gastric cancer. Based on a large, population-based, prospective study, we recently reported a null association between dietary isoflavone intake and gastric cancer. However, epidemiologic studies using blood concentrations of isoflavones might better reflect the effect of isoflavones on gastric cancer carcinogenesis than dietary assessment. We therefore conducted a nested case-control study within the Japan Public Health Center-Based Prospective Study. Participants were followed-up from 1990 to 2004. Among 36,745 participants who answered the baseline questionnaire and provided blood samples, 483 gastric cancer cases matched to 483 controls were used in the analysis. ORs and 95% CIs were estimated with a conditional logistic regression model. The overall distribution of plasma isoflavone concentrations was not associated with the development of gastric cancer. Compared with groups with the lowest plasma concentrations (reference groups), the groups with the highest daidzein and genistein concentrations had adjusted ORs and 95% CIs of 1.11 (0.74-1.66; P-trend = 0.6) and 0.96 (0.64-1.44; P-trend = 0.9), respectively. The results did not change when analysis was based on sex, subsite, or histological type. We found no association of plasma isoflavone concentrations with gastric cancer risk. Our data support the previously observed null association between isoflavone intake and gastric cancer risk.

Plasma Isoflavones and Risk of Primary Liver Cancer in Japanese Women and Men with Hepatitis Virus Infection: A Nested Case–Control Study

“…18): plasma isoflavone concentrations seemed to be maintained in Japanese who like isoflavone-rich foods. Our earlier work within the JPHC Study on the associations between isoflavones and cancers in other sites supports this assumption, with similar associations observed between the results of a cohort study using a food-frequency questionnaire and those of a nested casecontrol study using plasma concentrations (19)(20)(21)(22)(23)(24)(25)(26). Therefore, the present results indicate a possibility that plasma concentrations of isoflavones do not reflect dietary intake of isoflavones in people infected with hepatitis virus.…”

Soy isoflavone intake and stomach cancer risk in Japan: From the Takayama study

“…Studies among Western populations might not have detected significant associations due to the quite low intake of isoflavones among the majority of their participants (at most 10 mg/day), although estimates of nutrition intake should not be compared when calculated by different questionnaires. In addition, one nested case‐control study that measured plasma isoflavone concentrations observed associations between a decreased risk of stomach cancer and higher blood levels of isoflavone in Koreans, whereas another study of Japanese found no association . The inverse associations between soy isoflavone and stomach cancer should be further verified in different epidemiological studies.…”

Genistein and Cancer: Current Status, Challenges, and Future Directions

“…The beneficial role of soybean products against gastric cancer remains debatable from an interventional point of view. A nested case-control study within the Korean Multicenter Cancer Cohort suggested that high serum concentrations of isoflavones were associated with a decreased risk of gastric cancer (115); on the contrary, a parallel nested case-control study within the Japan Public Health Center-Based Prospective Study indicated a null association between isoflavone intake and gastric cancer risk among Japanese men and women (116).…”