As tumors grow, they often build blood vessels that connect to the body’s circulatory system. The vessels provide conduit for nutrients that tumors need to continue their expansion. Drugs that block the process of blood-vessel creation, known as angiogenesis, have been approved to treat certain types of colon, lung, and breast tumors, as well as other cancers.

Research suggests that compounds found in certain foods, such as green tea, red grapes, kale, and artichokes may also inhibit angiogenesis. But that doesn’t mean such foods are a substitute or replacement for prescribed therapies, according to Dana-Farber Cancer Institute nutritionist Stacy Kennedy, MPH, RD, CSO, LDN.

Why? Research so far in this area has been done in laboratory cell samples or animal models, not clinical trials involving patients with cancer. As a result, the ability of foods containing angiogenesis-inhibiting compounds to actually slow or prevent tumor growth in people remains an open question.

Secondly, choosing foods solely because they may inhibit angiogenesis represents too narrow a view of healthy eating, according to Kennedy. “Many of the compounds that have been found to have anti-angiogenic activity are found in plants,” she says. “A well-balanced diet consists of a variety of plant-based foods—particularly dark green leafy vegetables, fruits, nuts, seeds, and legumes—as well as fish and other lean protein.”

A healthy diet, such as the one Kennedy describes, can provide a range of benefits for cancer patients, potentially by helping to reduce inflammation and manage common side effects of treatment, such as constipation and fatigue. The possibility that some of these foods may also interfere with tumor angiogenesis could be an additional motivation for including them in one’s diet, but should not be a person’s sole motivation for eating a plant-heavy diet, Kennedy emphasizes.

Concrete answers to whether foods with angiogenic-blocking compounds can actually benefit patients may emerge from studies like one recently launched by Harvard University, in which investigators are exploring whether patients who respond better to treatment than expected have certain dietary, environmental, or attitudinal aspects in common.

This article was originally published on July 24, 2018, by Dana-Farber Cancer Institute. It is republished with permission.