The Mayo study enrolled 603 patients who were newly diagnosed with Non-Hodgkin lymphoma as well as 1,007 matched cancer-free "control" participants. Researchers asked the participants to answer a food questionnaire about their usual intake of over 120 food items two years prior to their cancer diagnosis or enrollment into the study (controls). They also asked about use of a variety of supplements. Vitamin K intake was estimated from this data.

While there was a clear trend showing that a greater intake of vitamin K from dietary sources was associated with a lower risk of Non-Hodgkin lymphoma, the use of vitamin K supplements presented a slightly different picture. Increasing intake of vitamin K from supplements did protect against Non-Hodgkin lymphoma, but reached a point where the highest intake offered no reduction in risk. "The significance of this finding is unclear," notes Dr. Cerhan, "but suggests that taking high doses of supplements is unlikely to be helpful." Dr. Cerhan also notes that people taking certain oral anticoagulants or seizure medications should closely follow their physician's dietary recommendations with respect to vitamin K intake, since vitamin K can interfere with these drugs.

"Whether the protective effect we observed is due to vitamin K intake, or some other dietary or lifestyle exposure, cannot be definitely assessed in this study," notes Dr. Cerhan. "But these findings add to a lot of other data that support a diet that includes plenty of green leafy vegetables in order to prevent many cancers as well as other diseases."

Source: Mayo Clinic