Vitamin K may reduce risk of non-Hodgkin's lymphoma

WASHINGTON In the first study of vitamin K and non-Hodgkin's lymphoma risk, researchers at the Mayo Clinic campus in Minnesota have found that people who have higher intakes of vitamin K from their diet have a lower risk of developing non-Hodgkin's lymphoma.

“These results are provocative, since they are the first work we have done on the connection between vitamin K and non-Hodgkin's lymphoma, and this is a fairly strong protective effect,” stated the study’s lead investigator, James Cerhan, a cancer epidemiologist. “However, as with all new findings, this will need to be replicated in other studies.”

Non-Hodgkin's lymphoma is a cancer of the immune system and is the most common hematologic malignancy in the United States.

Researchers at the Mayo Comprehensive Cancer Center are studying the connection between diet and non-Hodgkin's lymphoma risk, and they became interested in a potential role for vitamin K. While vitamin K is best known for its essential function in several proteins involved in blood clotting (the name of the vitamin is derived from the German word “Koagulations”), it also appears to be important in other biological processes, including inhibition of inflammatory cytokines thought to play a role in non-Hodgkin's lymphoma, as well as pathways involved in cell cycle arrest and cell death.

At the 101st Annual Meeting of the American Association for Cancer Research, researchers reported that the risk of developing non-Hodgkin's lymphoma was approximately 45% lower for participants who had vitamin K intakes in the top quartile of intake in the study (more than 108 ug/day), compared to participants who had intakes in the bottom quartile (less than 39 ug/day). This association remained after accounting for other factors such as age, sex, education, obesity, smoking, alcohol use and intake of foods with high amounts of antioxidants.

The Mayo study enrolled 603 patients who were newly diagnosed with non-Hodgkin's 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's lymphoma, the use of vitamin K supplements presented a slightly different picture. Increasing intake of vitamin K from supplements did protect against non-Hodgkin's lymphoma, but reached a point where the highest intake offered no reduction in risk. “The significance of this finding is unclear,” Cerhan said, “but suggests that taking high doses of supplements is unlikely to be helpful.” Cerhan also noted 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,” Cerhan said. “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.”

The study was funded by the National Cancer Institute.