In a study of more than 800 U.S. adults with and without non-Hodgkin's lymphoma (NHL), researchers found that those who ate the most vegetables had a 42 percent lower risk of the cancer than those with the lowest intakes.
In particular, leafy greens like spinach and kale, and cruciferous vegetables like broccoli, Brussels sprouts and cauliflower, seemed to be protective.
Similarly, the study found, two nutrients found in green vegetables -- lutein and zeaxanthin -- were related to a lower NHL risk. The same was true of zinc, a mineral obtained through meat, nuts and beans.
The "working hypothesis" is that the antioxidant activity of these vegetables and nutrients explains the connection, said study co-author Dr. James R. Cerhan of the Mayo Clinic College of Medicine in Rochester, Minnesota.
NHL begins in the lymphatic system, a component of the immune system that carries disease-fighting white blood cells called lymphocytes. The cancer arises when these cells become abnormal and begin to divide uncontrollably.
Antioxidants help protect cells from such damage by neutralizing molecules called reactive oxygen species. These substances are byproducts of normal body processes, as well as environmental exposures like cigarette smoke, and in excess they can damage body tissue and lead to disease.
The new findings, published in the American Journal of Clinical Nutrition, suggest "yet another benefit" of eating your vegetables, Cerhan told Reuters Health.
Vegetables and fruits are probably the best way to get antioxidants, he said, because these foods have a host of other nutrients that may all work together to bestow health benefits.
The study included 466 adults with NHL who were enrolled in a national cancer registry, along with 391 cancer-free adults who were matched to patients by age, race and sex. Both groups answered questions about their diet and other health and lifestyle factors.
In general, those who ate more than 20 servings of vegetables a week had a 42 percent lower risk of NHL than those who ate eight weekly servings or fewer. When the researchers looked at specific nutrients, lutein and zeaxanthin stood out; people with the highest intakes were about half as likely as those with the lowest to develop NHL.
This makes sense, Cerhan noted, given that the major vegetable sources of these antioxidants, including spinach, kale and broccoli, also seemed particularly protective against the cancer.
Zinc, a mineral important to immune function, was also linked to a lower lymphoma risk. But Cerhan said this has not been seen in previous studies, and more research is needed to know what to make of it.