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The Flavonoid Quercetin Also Shown To Reduce Colon Cancer

James Meschino DC, MS, ROHP

More recently, experimental, animal and human studies have demonstrated that supplementation with the flavonoid quercetin (a common constituent of many fruits and vegetables) has demonstrated an ability to prevent colon cancer development, and reduce the replication ability of existing human cancer cells. More specifically, the addition of quercetin to cultured human colon cancer cells (Caco – 2 cells – human adenocarcinoma colon cancer cells) inhibited the ability of the colon cancer cells to replicate. After exposure to quercetin cell replication rates decreased to 51.3% compared to cancer cells not exposed to quercetin.

Some animal studies have shown that oral administration of quercetin reduces the development of colon cancer in animals also exposed to cancer causing agents known to induce colon cancer development (animals given the quercetin showed significantly less cancers than those not given quercetin).  Quercetin is a potent antioxidant and has anti-inflammatory effects. Experimental studies indicate that quercetin can cause undifferentiated cancer cells lines to differentiate and has been shown to protect against hydrogen peroxide induced DNA strand breaks in human adenocarcinoma cells (Caco-2 cells). A study in The European Journal of Nutrition (M.J. van Erk et al/2005) demonstrated that quercetin inhibited proliferation of human colonic adenocarcinoma cells (Caco-2 cells) via a number of biological actions. These include down regulation expression of cell cycle genes (e.g. CDC6, CDK4 and cyclin D1), down regulation of cell proliferation and induced cell cycle arrest

All of this evidence prompted researchers to test the ability of quercetin to prevent colon cancer in human subjects, who are known to be at high risk for colon cancer development. Individuals with an hereditary condition known as familial adenomatous polyposis are known to have a high risk of developing colon cancer, as they produce numerous polyps in the large bowel, which are prone to undergoing conversion to malignancy. In a study involving 5 patients with familial adenomatous polyposis (FAP: an autosomal-dominant disorder characterized by the development of hundreds of colorectal adenomas and eventual colorectal cancer) and prior colectomy (4 with retained rectum and 1 with an ileal anal pouch), supplementation with curcumin and quercetin reduced the number and size of ileal and rectal adenomas. The patients received oral supplementation with 480mg curcumin and 20mg quercetin, three times a day.

At treatment end, the number and size of polyps decreased in all five patients, with a 60.4% mean decrease in the number of polyps and a 50.9% mean decrease in the size of polyps. Additionally, minimal adverse side effects and no laboratory abnormalities were observed in the patients during the treatment period. Thus, the findings of this study indicate that supplementation with curcumin and quercetin may reduce the number and size of ileal and rectal adenomas in patients with FAP and may help to prevent colon cancer development in general. Experimental evidence has shown the mechanism of action through which quercetin can protect against colon cancer development: slows colon cancer cell replication, induces programmed cell death of cancer cells (apoptosis), encourages normal differentiation of colon cells and colon cancer cells, and acts as an antioxidant and anti-inflammatory agent. Curcumin was tested with quercetin in this study because it too, shares many of the same anti-colon cancer properties as quercetin, according to experimental and animal studies

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