Vitamin K is a fat-soluble vitamin that has three forms: phylloquinone (vitamin K1), menaquinones (vitamin K2), and a synthetic form (vitamin K3) that isn’t for human consumption. Vitamin K is best known for its role in helping blood clot, and it also is involved in bone health.
Several recent studies have found a link between vitamin K and prostate health, and both reports drew their data from the large European Prospective Investigation into Cancer and Nutrition (EPIC-Heidelberg) study, which evaluated more than 11,000 men. In one spin-off study of EPIC, the researchers looked at the association between dietary intake of phylloquinone and menaquinones and total and advanced prostate cancer. (Nimptsch 2008) During a mean follow-up of 8.6 years, a total of 268 cases of prostate cancer were identified, including 113 advanced cases. Menaquinones from dairy foods had a stronger preventive effect with advanced prostate cancer than did menaquinones from meat, while phylloquinone intake had no impact. These findings were then confirmed in a subsequent study by the same researchers. (Nimptsch 2009)
The RDA for males age 19 years and older is 120 mcg. Vitamin K1 is found in green leafy vegetables (e.g., lettuce, broccoli, spinach) and makes up about 90 percent of the vitamin K in a typical American diet. Vitamin K2 can be found in meat and fermented foods such as cheese and natto. Vitamin K deficiency is very rare. As a supplement, water-soluble chlorophyll is the most common type available over the counter, and it can be purchased in tablet, capsule, and liquid forms. Consult your healthcare provider before taking vitamin K, especially if you are taking blood thinning medication, as the nutrient reduces the medication’s effect.
Nimptsch K et al. Dietary intake of vitamin K and risk of prostate cancer in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Heidelberg). Am J Clin Nutr 2008 Apr; 87(4): 985-92.
Nimptsch K et al. Serum undercarboxylated osteocalcin as biomarker of vitamin K intake and risk of prostate cancer: A nested case-control study in the Heidelberg Cohort of the European Prospective Investigation into Cancer and Nutrition. Cancer Epidemiol Biomarkers Prev 2009 Jan. 18(1): 49-56.