Vegetable, lutein, zeaxanthin, and zinc intake linked with lower risk of non-Hodgkin lymphoma
In a study published in the June, 2006 issue of the American Journal of Clinical Nutrition, researchers from the Mayo Clinic College of Medicine, the National Cancer Institute, the Fred Hutchinson Cancer Research Center and other institutions found a lower risk of non-Hodgkin lymphoma (NHL) associated with a greater intake of vegetables and the dietary nutrients lutein, zeaxanthin and zinc. Non-Hodgkin lymphoma is an immune system cancer characterized by the proliferation of T or B cells, the incidence of which has increased over the past several decades for reasons unknown.
The current analysis included 466 men and women between the ages of 20 and 74 with non-Hodgkin lymphoma and 391 age, gender, race, and location-matched control subjects. Questionnaires and personal interviews were used to collect information on the quantities of various foods and nutritional supplements consumed over the previous year, from which daily nutrient intake was calculated.
Individuals whose vegetable intake was in the top one-fourth of participants were found to have a 42 percent lower risk of non-Hodgkin lymphoma than those whose intake was in the lowest fourth. When leafy green and cruciferous vegetable intake were separately analyzed, similar associations with NHL risk were found. Participants among the top 25 percent of lutein and zeaxanthin intake experienced a 46 and 42 percent lower risk of the disease, and those whose zinc intake was highest experienced a 42 percent reduction compared to those in the lowest quarter.
The authors observed that vegetables contain not only lutein and zeaxanthin which were associated with a reduced risk of non-Hodgkin lymphoma in this study, but that they also provide folate, involved in DNA synthesis and repair, and compounds that detoxify carcinogens. The association of zinc with a reduction in NHL risk could be due to its ability to displace DNA-bound iron, which reduces iron-catalyzed hydroxyl radical production that damages DNA. Zinc also has an action on various compounds involved in immune system development and reactivity.
To the authors’ knowledge, the study is the first epidemiologic report of the association between non-Hodgkin lymphoma and zinc. The current findings, in combination with those of other studies, “suggest that higher intakes of vegetables, in general, and specific nutrients that function in antioxidant-related pathways, in particular, may reduce the risk of developing NHL,” they write. “If so, dietary change may be one of a small number of modifiable influences on lymphoma risk,” they conclude.
More than 60,000 Americans were diagnosed with some form of lymphoma in 2004, and more than 20,000 died from their disease. Lymphomas are linked to a variety of risk factors, including diet, medical history, environmental exposure to chemicals, and infections. To date, conventional medical treatment for lymphoma has been based on combinations of chemotherapy, radiotherapy, and stem cell therapy. However, new treatments for lymphoma now add to these traditional therapies the use of substances that can specifically target the delivery of radiotherapy to lymphoma cells (radioimmunotherapy) or activate the immune system to kill lymphoma cells (chemoimmunotherapy).
Non-Hodgkin lymphoma is more common in individuals with weakened immune systems (Zhang S et al 1999; Zhang SM et al 2000). Clinical studies have now shown that diets rich in animal protein and fats, which are thought to diminish immune function (Calder PC et al 2002; Jones DE 2005; Plat J et al 2005), are associated with an increased risk of developing NHL (Chang ET et al 2005; Chiu BC et al 1996; De SE et al 1998; Zhang S et al 1999). Clinical studies have also shown that diets rich in fruits and vegetables, which are thought to enhance immune cell function (Gaisbauer M et al 1990; Rossing N 1988; Loghem JJ 1951), are associated with a reduced risk of developing NHL (Zhang SM et al 2000; Zheng T et al 2004).
Nutritional supplements with demonstrated activity against lymphoma cells include:
The carotenoids zeaxanthin and lutein, found in the macular region of the eye, help shield eyes from sunrays, computer screens and other harmful forms of light that over time can cause photo-oxidative damage to the eyes. These fat-soluble antioxidants are uniquely able to absorb the most damaging portions of the light spectrum, helping to protect the lens, retina, and macula. In fact, zeaxanthin and lutein have been called "conditionally essential nutrients" because of their critical protective functions in the eye.
Zinc is a mineral essential for formation of superoxide dismutase, one of the body’s most important free radical scavengers and one that cannot be directly supplemented. Zinc also promotes wound healing, immune function, taste sensitivity, protein synthesis, insulin production, and reproduction including organ development and sperm motility.