Vitamin K Intake May Lower Risk of Non-Hodgkin Lymphoma
Eat lots of green leafy vegetables: you hear it all the time. Now researchers are saying it again, and this time it is because they have found a possible connection between higher vitamin K intake and a lower risk of developing non-Hodgkin lymphoma.
Humans are not able to make vitamin K, so they must get it from dietary sources. The richest sources of vitamin K1 in the diet are leaf lettuces, spinach, cabbage, broccoli, and soybeans, although it is also found in lower amounts in some fruits and other vegetables, as well as whole wheat. Vitamin K2 is produced by bacteria in the intestinal tract.
The main function of vitamin K is to help with clotting of blood, although it may also have a role in cell death and in inhibiting inflammatory substances believed to be involved with non-Hodgkin lymphoma. Researchers at the Mayo Clinic in Minnesota set out to examine that possibility.
The Mayo Clinic study involved 603 patients who had recently been diagnosed with non-Hodgkin lymphoma, as well as 1,007 controls who were cancer-free. All of the participants completed a food questionnaire about their typical intake of more than 120 food items as well as their supplement use during the two years before they received their diagnosis or were enrolled in the study.
The researchers noted that the risk of developing non-Hodgkin lymphoma was about 45 percent lower for individuals who had consumed more than 108 micrograms of vitamin K daily compared with participants who had consumed less than 39 micrograms daily. This reduction remained the same after the investigators accounted for age, sex, obesity, smoking, alcohol use, and consumption of foods high in antioxidants. The suggested Adequate Intake of vitamin K is 90 to 120 micrograms for adults.
James Cerhan, MD, PhD, a cancer epidemiologist, called their results “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.”
Non-Hodgkin lymphoma refers to a group of cancers that affect the lymphocytes (white blood cells). Several types of non-Hodgkin lymphoma can develop, including aggressive (fast-growing) and indolent (slow-growing), and those formed from either B-cells or T-cells. The prognosis and treatment depend on the type and stage of disease an individual has. For 2009, the National Cancer Institute estimated that 65,980 new cases of non-Hodgkin lymphoma would be diagnosed, and that 19,500 people would die of the disease.
While the Mayo Clinic study found a relationship between a higher intake of vitamin K from dietary sources and a lower risk of non-Hodgkin lymphoma, the use of vitamin K supplements provided protection only to a point, suggesting that high doses of the supplement are probably not helpful, according to Dr. Cerhan.
Dr. Cerhan admits that the protective effect he and his team observed in this study regarding non-Hodgkin lymphoma cannot be definitely attributed to vitamin K intake. However, “these findings add a lot to other data that support a diet that includes plenty of green leafy vegetables in order to prevent many cancers as well as other diseases.”
Mayo Clinic, Minnesota, news release April 19, 2010
National Cancer Society