In a prospective study of 24,340 Europeans (aged 35-64 years) who were free of cancer at baseline, during a median follow-up period of more than 10 years, 1755 cases of cancer were documented. Dietary intake of menaquinones (vitamin K2) was inversely associates with overall cancer incidence (hazard ration for the highest vs. the lowest quartile of intake = 0.86; 95% confidence interval [CI] 0.73 - 1.01; p for trend = 0.080. The association was stronger for cancer mortality (hazard ration = 0.72l 95% CI, 0.53 - 0.98; o fir trend = 0.03).
Cancer risk reduction with increasing intake of menaquinones was more pronounced in men than in women, and was driven mainly by significant inverse associations with prostate (p for trend = 0.03) and lung (p for trend = 0.002) cancer. No association was found between phylliquinone (vitamin K1) intake and cancer incidence.
Studies in animals and humans suggest that vitamin K2 has an anticancer effect, a finding that is supported by the present observational study. The main dietary source of vitamin K2 is cheese; other sources include butter, egg yolks, meats, and natto (fermented soybeans). In contrast to the apparent beneficial effect of vitamin K2, vitamin k1 (which is present in dark green vegetables and some vegetable oils) did not appear to be protective. One should not conclude from this study that we should be eating lots of dairy products and meat and avoiding vegetables. However, the findings support the possibility that consuming some vitamin K2 (either in food or supplements) may reduce the incidence of certain types of cancer.
Nimptsch K, et. al. Dietary vitamin K intake in relation to cancer incidence and mortality: results from the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Heidelberg). Am J Clin Nutr. 2010;91:1348-1358.
Reprinted with exclusive permission of The Townsend Letter for Doctors & Patients August/September 2010.