Specific Plants Protect Against Specific, Not All, Cancers
August 29, 2012 (Montreal, Quebec) — Not all fruits and vegetables protect against cancer; rather, specific plants — mostly vegetables — protect against specific cancers, according to research presented here at the Union for International Cancer Control World Cancer Congress 2012.
An unhealthy diet — a key promoter of certain cancers — is always associated with fruit and vegetable deficiency, noted Richard Beliveau, PhD, from the University of Montreal, University of Quebec at Montreal, and McGill University in Quebec. Fruit and vegetable deficiency, in turn, is associated with the formation of a carcinogenic environment, he added.
“Plants do not produce chemicals to help us fight cancer; essentially, plants produce an arsenal of toxic chemicals that kill yeast, bacteria, and insects. Out of this huge chemodiversity, research has shown that some of these chemicals have potent anticancer properties,” he explained.
However, these anticancer properties are associated with specific fruits and vegetables, not all of them,” Dr. Beliveau reported.
Probably the best example of a phytochemical that serves as an antiinflammatory is curcumin. “Turmeric is the most potent source of curcumin, and curcumin is the most potent antiinflammatory phytochemical we know,” Dr. Beliveau told Medscape Medical News.
These antiinflammatory properties could prevent cancer from developing, he suggested. It is widely recognized that an inflammatory stimulus created by diseases, such as inflammatory bowel disease, is a major risk factor for colorectal cancer. Similarly, infection with Helicobacter pylori can lead to chronic gastritis and, in some cases, gastric cancer.
The diet-derived phytochemical epigallocatechin gallate, found in green tea, targets tumor invasion and metastasis, as well as angiogenesis. Resveratrol from grapes has been found to possess strong proapoptotic activity against cells isolated from a variety of tumors; this activity correlates with the inhibition of tumor growth in animals. Broccoli has sulforaphane, which kills cancer cells directly, Dr. Beliveau noted.
There is robust evidence that specific phytochemicals targeting carcinogenic pathways lead to significant reductions in specific types of cancer. For example, in prospective studies done with tens of thousands of participants, researchers have linked the consumption of cruciferous vegetables (cauliflower, broccoli, kale) to reductions of approximately 50% in both bladder and prostate cancer, and of about 30% in lung cancer.
Tomato consumption has been associated with a 25% reduction in prostate cancer, and the consumption of leafy green vegetables with generous amounts of dietary folate have been shown to reduce the risk for pancreatic cancer by approximately 75%.
“Just as you don’t give vinblastine to treat all cancers, you don’t protect against all cancers with the same food,” Dr. Beliveau said. “When we look at cancer prevention, we need to look at the type of vegetables that are consumed, not the quantity. If we consume specific foods in combination, rates of protection against cancer should be higher,” he noted.