The Antitumor Effects of Quercetin

• Quercetin has an apoptotic effect on aging cells that may help prevent or be helpful in the treatment of cancer; years of research have also demonstrated it prevents chemically induced cancer and lung cancer, and inhibits the proliferation of cancer cells
• Quercetin has also demonstrated the ability to mitigate some of the effects of sleep deprivation, including mood changes, anxiety, memory performance, hyperactivity and cognitive impairment
• The combination of quercetin, bromelain, vitamin C and zinc has emerged in at least two of the successful protocols used to treat COVID-19; historically, data have shown it is effective against influenza, zika, hepatitis B and rhinovirus responsible for the common cold
• Quercetin is not water-soluble and is poorly absorbed unless it is paired with bromelain or vitamin C. Quercetin has shown positive benefits for heart disease, high blood pressure, metabolic syndrome, NAFLD and arthritis
• Quercetin is found in onions, red grapes and green tea. 

It could be a useful supplement to stock in your medicine chest to use when you believe you may be getting an upper respiratory infection

Quercetin is an antioxidant flavonol that's found in foods such as red grapes, green tea, elderflower and onions, to name a few.1 As the health benefits of the supplement become more widely known, the market has grown rapidly.2 According to market research, quercetin market was worth $261.12 million in 2020 and is expected to reach $406.58 million in 2027.

Quercetin has a wide range of benefits, which has made it useful for a variety of different health conditions. In the last two years, the antiviral benefits of quercetin have been the focus of many studies.3 However, there are other, lesser-known benefits, including the effects as a senolytic agent against senescence-mediated cancer growth.4
It is perhaps most well-known as a strong antioxidant5 and antiviral.6 For example, Elderflower extract, which is rich in quercetin, is a traditional tonic used to boost immunity. In supplement form, quercetin has been used to prevent and treat the common cold and influenza.7

According to Mount Sinai,8 quercetin should be used with caution as it may interact with certain antibiotics by reducing the effectiveness of the drug. It may also enhance the effect of some blood thinners, which can increase your risk of bleeding. In addition to these, it may interact with corticosteroids, digoxin, cyclosporine and fluoroquinolones.

Quercetin Effect on Senescence-Mediated Cancer Cells
A paper9 published in August 2022 in Nutrition Research analyzed the pro-apoptotic effect that quercetin has on aging cells. The paper reviewed preclinical and early phase data using quercetin as a senolytic agent and found the data showed it was effective in “preventing or alleviating cancer formation.”

The authors reviewed the importance of cellular aging in the development of cancer cells and the effect that quercetin may have on the suppression of cancer cell proliferation. Research has found that cellular aging can suppress tumor development, but paradoxically can also enhance cancer development.10

Cellular senescence is a dynamic and multi-step process that is associated with alterations in metabolic activity and gene expression.11 This can compromise tissue regeneration and contribute to aging. On the other hand, by removing senescent cells, age-related dysfunction can be attenuated and potentially extend the lifespan.

One paper12 published in 2008 recognized that animal studies had demonstrated quercetin could prevent chemically-induced cancer growth and epidemiological studies found it was associated with preventing lung cancer. One study13 focused on the effect that physiologically attainable doses of quercetin had on the inhibition of cancer cell proliferation. The researchers believed their study demonstrated quercetin had chemopreventive properties.

Lab studies14 have also demonstrated that quercetin is a strong antioxidant and has pro-apoptotic effects on tumor cells, with the ability to block growth at different phases of the cell cycle. Research15 also has demonstrated that quercetin can promote the loss of cell viability and autophagy through several pathways, including those involving mitochondrial function and glucose metabolism.

Data16 indicate that quercetin could play a role in cancer treatment as it reportedly has synergistic effects in combination with chemotherapy agents or radiation therapy. Quercetin has also shown promising results with chemoprotective and radioprotective properties, by protecting normal cells against the effects of chemotherapy and radiation therapy.

One paper17 identified some of the anti-inflammatory, antioxidant and antiproliferative properties quercetin has that enhances breast cancer treatment, while another18 evaluated its effect on the treatment of ovarian cancer, which is a serious cancer growth and threat to...

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