Vitamin K -- found in green leafy vegetables -- may protect against non-Hodgkin lymphoma, U.S. researchers said. Researchers at the Mayo Clinic in Rochester, Minn., said the risk of developing non-Hodgkin lymphoma -- cancer of the immune system -- was approximately 45 percent lower for those whose vitamin K intake was in the top quarter, vs. those whose intake of the vitamin was in the bottom quarter, according to a report of the United Press International (UPI). The fat-soluble vitamin known for its effect on blood clotting seems to play a role in inhibiting inflammatory cytokines which may play a role in the disease, the researchers said. "These results are provocative, since they are the first work we have done on the connection between vitamin K and non-Hodgkin lymphoma, and this is a fairly strong protective effect," lead investigator Dr. James Cerhan said in a statement. "However, as with all new findings, this will need to be replicated in other studies." Cerhan and colleagues surveyed the diets and supplements for the last two years of 603 newly diagnosed Non-Hodgkin lymphoma patients as well as 1,007 matched cancer-free controls. The researchers cautioned vitamin K can interact with certain drugs -- such anti-coagulants or seizure medications -- and patients taking them need to follow their physician's recommendations on diet.