Citrus Flavonoids And Cancer Prevention
Our grandmothers were telling our parents to eat their vegetables and fruits, long before science could explain why it was so important. A diet rich in vegetables and fruits has long been associated with a reduced risk of cancer, and colorectal cancer in particular. Yet, while the association was shown in statistical analyses, the exact mechanism or causal relationship remains unknown.
A paper that raises intriguing possibilities was published by researchers at South Dakota State University and the University of Kentucky, in 2019 in the journal Molecules, the leading international peer-reviewed open access journal of chemistry.
Flavonoids And Metabolism
Flavonoids are compounds found in many plants, including citrus fruits. They produce the unique color and taste profiles of each citrus fruit. While the research in this area is still nascent, early test results indicate that flavonoids act as antioxidants, which means they protect cells from oxidant damage. That may be why their consumption is associated with a lower risk of cancers, but that’s not the whole picture.
• The tests were conducted in vitro – in a lab – meaning the way flavonoids act in the body is still unproven;
• We do know that the body only absorbs 15% or so of the flavonoids it ingests, which means it is difficult to discern their action.
How and what effect do they have on the body?
The Metabolite Theory
The research paper posits what researchers call “the metabolite hypothesis”. Essentially, the theory, which is supported by the limited evidence so far, is this:
• If only 15% of the flavonoids are directly absorbed into the bloodstream, 85% proceed to the intestines, where they are broken down by bacterial enzymes;
• The process produces other compounds, called metabolites, and the researchers identified several simple phenolic acids, specifically hydroxybenzoic acids, or HBAs, that may contribute to colorectal cancer prevention.
“Plants also have the capacity to make these metabolites. Fruits and vegetables are loaded with free HBAs, which act as antioxidants and also help the plants fight infections,” states associate professor Jayarama Gunaje of SDSU’s Department of Pharmaceutical Sciences in the report.
Some limited study on animal subjects also confirmed that flavonoid metabolites can inhibit cancer cell growth, with the details in the March 2019 issue of Cancers.
While it’s only one step so far, it points the way to the need for more research into this very exciting possibility.