The connections between vitamin K and cancer are still being studied. At present there appears to be no conclusive evidence finding that vitamin K prevents cancer or assists as a cure for it. In the late 1990s and 2000s, however, there have been studies suggestive of a link between the use of vitamin K and a reduction of the risk or susceptibility to certain types of cancer, particularly liver and prostate cancer. There is also some evidence that vitamin K may aid patients who have undergone specific types of cancer surgery.
Vitamin K is an essential nutrient used by the liver to make proteins that aid in blood clotting and prevent abnormal bleeding. The vitamin takes its name from the German word for clotting, “koagulation.” In its natural form, Vitamin K is found in green leafy vegetables such as cabbage, broccoli, spinach, and turnip greens. Soybean oil, olive oil, and canola oil have smaller amounts of the vitamin. A variant of Vitamin K, called MK7 is manufactured by intestinal bacteria but can also be found in fermented products like cheese.
Current scientific evidence does not conclusively support a connection between vitamin K and cancer in terms of the prevention or treatment of the disease. But research over the last decade has begun to find important connections between Vitamin K and liver and prostate cancer. It appears there is some scientific agreement that these possible links are important enough to warrant further and more in depth study.
In 1998, an animal study observed that a synthetic form of vitamin K named compound 5 could possibly slow the advance of cancer cells. Later studies suggested that other forms of vitamin K may fight cancer cells in mice. A clinical trial conducted in 2006 of the vitamin K subgroup K2 indicated that it could reduce liver cancer reoccurring in patients following surgery for the cancer. Additionally, a clinical trial in Japan involving vitamin K and cancer of the liver found that vitamin K supplements may lower the risk of cancer in women suffering from cirrhosis of the liver.
A European study published in 2008 found a higher risk of prostate cancer in men with low vitamin K intake. It was pointed out, however, that people with low vitamin K intake generally have overall a very poor diet, which would also affect their cancer risks in general. The most promising evidence of a positive connection between vitamin K and cancer appears to be in relation to liver cancer. A 2010 research paper published in the American Journal of Nutrition found that people with the highest intake of vitamin K have the lowest risk of liver cancer and a lower mortality rate if they do contract the cancer.