Flavanols in Foods Help Prevent Colon Cancer
Scientists have found that a number of flavanol compounds in plants help prevent colon cancers and rectal cancers – collectively called colorectal cancer.
Flavonols in quince halt cancer growth
In a 2018 study from Poland’s Medical University of Lodz, researchers studied human colon cancer cells. In particular, they tested an extract of the Japanese Quince fruit (Chaenomeles japonica). The extract isolated a collection of compounds called flavanols. This flavanol extract contained polyphenols such as procyanidin monomers and oligomers. These are components of the fresh quince fruit as well as other foods, as we’ll discuss below.
The researchers found that the flavanol extract significantly blocked the ability of the cancer cells to continue to expand. After 72 hours, they found the quince extract blocked the genetic expression of proteins by up to 77 percent. It also inhibited the MMP-9 levels in the cells. MMPs are linked to tumor progression. The quince extract also inhibited the production of key enzymes that allow the cancer cells to migrate and expand.
Okay, but do flavanols protect against colon cancer when people eat more foods containing them on a daily basis?
Colorectal cancer research follows 400,000 people
A review of research that included nearly 400,000 people from China’s National Center of Colorectal Surgery has determined that certain phytonutrients, specifically flavonoids and flavanols, have the ability to significantly reduce the risk of colorectal cancer.
After an extensive review of the evidence, the researchers narrowed the research down to eight studies, which included 390,769 people. These included a range of protocols, including large population studies as well as controlled randomized studies.
The researchers utilized the Cochrane library and the Cochrane protocol for reviews. This process helps quantify the results – often creating more conservatism among the results due to strict result comparisons.
Flavanols protect against cancer
The research found that foods containing flavanols – more technically referred to as flavan-3-ols – resulted in a significant reduction in incidence in colorectal cancer. The greater the flavanol consumption, the greater the association. More specifically, they found that greater consumption of epicatechin – a flavanol – significantly decreases the risk of colorectal cancer.
Flavanols include the category of catechins, which includes epicatechin, gallocatechin and epigallocatechin. Depending upon the molecular classification, they can also include kaempferol. Collectively these and others are also referred to as polyphenols. Plant polyphenols like catechins are found in many fruits and vegetables and vinegar. They are also found in herbal teas and green tea, as well as cocoa (from Theobroma cacao). Significant flavanol content has also been found in apples, onions and some beans.
The research also found that the consumption of procyanidins and phytoestrogens also reduced colorectal cancer incidence. The researchers characterized the association of these as “medium quality,” meaning there was a definite association between the consumption and colon cancer, but not as strong as the polyphenol association.
Two other phytocompounds found to reduce colorectal cancer was genistein and formononetin. These are considered isoflavonoids but also phytoestrogens because they have the ability to bind to the body’s estrogen receptors. This can be significant because as people age – especially women – estrogen availability slows and this can be pro-inflammatory. When phytoestrogens are in the diet, these can help dampen the effects of estrogen reduction as we age.
Good sources of flavanols
The phytoestrogens genistein and formononetin are significantly found in beans, soy, red clover and some whole grains.
The number of plant compounds – phytonutrients – available from a plant-based diet is gigantic. The researchers described more than 5,000 individual flavonoids that have been divided into more than ten different categories. The big six categories include isoflavonoids, flavones, anthocyanidins, flavan-3-ols, flavonols (note the “o” instead of a second “a”), and flavanones.
Flavanones are significant in citrus, while the flavones are in many vegetables and herbs. Anticancer parsley contains flavanols. Tree nuts – found to reduce colon cancer – are also high in flavanols. Legumes also contain flavanols. And several medicinal mushrooms contain anticancer flavanols. In addition, olives and olive oil contain anticancer flavanols.
One of the studies included in the review was from the U.S. National Cancer Institute. The study followed 1,905 people and their diet with an average age of 61. The researchers compared the consumption of 29 different flavonoids together with the incidence of the occurrence of adenomatous polyps – a frequent symptom of colorectal cancer. The research used colonoscopies to determine polyp incidence. This study also showed that switching to a high-fiber diet also significantly reduced polyp incidence and subsequent colorectal cancer.
Furthermore, the study found that colorectal cancer prevention occurred most significantly among those who consumed the higher levels of flavonol foods. In other words, just adding a few veggies to the diet won’t necessarily tip the scale.
Owczarek K, Hrabec E, Fichna J, Sosnowska D, Koziołkiewicz M, Szymański J, Lewandowska U. Flavanols from Japanese quince (Chaenomeles japonica) fruit suppress expression of cyclooxygenase-2, metalloproteinase-9, and nuclear factor-kappaB in human colon cancer cells. Acta Biochim Pol. 2017;64(3):567-576. doi: 10.18388/abp.2017_1599.
Jin H, Leng Q, Li C. Dietary flavonoid for preventing colorectal neoplasms. Cochrane Database Syst Rev. 2012 Aug 15;8:CD009350.
Bobe G, Sansbury LB, Albert PS, Cross AJ, Kahle L, Ashby J, Slattery ML, Caan B, Paskett E, Iber F, Kikendall JW, Lance P, Daston C, Marshall JR, Schatzkin A, Lanza E. Dietary flavonoids and colorectal adenoma recurrence in the Polyp Prevention Trial. Cancer Epidemiol Biomarkers Prev. 2008 Jun;17(6):1344-53.