Soy Intake Linked With Reduced Hepatocellular Carcinoma Risk

NEW YORK JUN 21, 2005 (Reuters Health) - Consuming miso soup and other soy foods may reduce the risk of hepatocellular carcinoma (HCC), according to the results of a study published in the June 10th issue of the International Journal of Cancer.

Dr. Gerald B. Sharp, of the National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, and colleagues conducted a case-control study within a cohort of Japanese A-bomb survivors to determine if consumption of soy foods reduces the risk of HCC.

The researchers compared the prediagnosis consumption isoflavone-rich miso soup and tofu to HCC risk.  The team adjusted for hepatitis B (HBV) and C (HCV) viral infection, which are major HCC risk factors in this population.

Included in the study were 176 confirmed cases of HCC diagnosed between 1964 and 1988, and 560 control subjects who died of diseases other than liver cancer.  Dietary information collected at least 2 years prior to diagnoses or death was examined.

Subjects who ate miso soup or tofu more than five times per week had a 50% lower risk of HCC compared with those who ate soy-containing foods no more than once per week.

The odds ratio for miso soup remained unchanged at 0.5 after adjusting for year of birth, sex, HBV, HCV and other variables.  The adjusted OR for tofu was 0.9.

"There was a statistically significant interaction (p < 0.0001) between sex and HCV in the etiology of HCC, with women being at greater risk than men," Dr. Sharp"s team writes.  Overall, 78% of female cases had HCV infection, compared with 37% of male cases.  Corresponding numbers for female and male controls were 7% and 11%, respectively.

The authors note that these findings are consistent with results of other studies.  The lower HCC risk associated with higher soy consumption intake "may reflect a counteracting effect of isoflavones on estrogen and testosterone levels that reduces HCC risk," the investigators suggest.

SOURCE:

• International Journal of Cancer 2005;115:290-295.