In humans, cancer is a life-threatening malignancy. Worldwide, cancer is the second leading cause of death posing a substantial burden globally. Nowadays, natural products are becoming a topic of research for drug discovery. High dietary consumption of fruits and vegetables has been found to reduce the risk of cancer.
Among natural compounds, quercetin has been identified as a significant therapeutic agent for preventing and healing cancer. It is one of the most abundant antioxidants in the diet and offers low toxicity, and predictable performance.
The beneficial effects of quercetin come from their ability to function as antioxidants inside your body and thus playing an essential role in helping your body combat free radical damage, which is associated with chronic diseases.
Let’s explore, how essential is to include quercetin-rich foods in the diet for cancer patients:
- What is quercetin?
- Sources of quercetin
- How much quercetin do you need?
- Anti-cancer effect of quercetin
- Mechanism of action of quercetin
What is Quercetin?
Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is a natural bioactive pigment that belongs to flavonoids.
Sources of quercetin
The flavonoid, quercetin is ubiquitously present in many fruits, vegetables, grains, and dried fruits. Foods that commonly contain this potent polyphenol include apples, onions, grapes, berries, citrus fruits, cherries, coffee, green tea, honey, raspberries, red wine, capers, and broccoli. It is also available as a dietary supplement in capsule and powder form.
How much quercetin do you need?
It is estimated that in humans, quercetin's daily consumption through numerous food sources ranges from 10 to 100 mg, depending on dietary habits. If selected highly purified extracts are used, quercetin intake may reach 500-1000 mg.
Anti-cancer effect of quercetin
Due to the chemopreventive effects witnessed in numerous in vitro and in vivo models, quercetin demonstrates substantial potential in oncology. It is also evident from the outcomes of recently done studies that the consumption of foods rich in quercetin is strongly related to reduced cancer risk. Accumulating evidence of quercetin also suggests cancer-preventive properties. In a review of test-tube and animal studies, the flavonoid quercetin was found to suppress cell growth and induce apoptosis in prostate tumor cells.
Other test-tube and animal studies depicted that quercetin repressed the proliferation of cancers such as lung cancer, liver cancer, breast cancer, blood cancer, bladder cancer, ovarian cancer, lymphoid cancer, adrenal cancer, prostate cancer, pancreatic cancer, gastric cancer, colorectal cancer, oral cancer, and thyroid cancer. Though these findings are promising, there is a requisition of human studies before quercetin can be advocated as an alternative treatment for cancer.
Mechanism of action of quercetin
Quercetin, a well-known plant flavonoid, plays a pivotal role as an anticancer agent. This therapeutic agent primarily targets proliferating tumor cells. Quercetin elicits a biphasic, dose-dependent clinical effect. At lower concentrations, this flavonoid acts as an antioxidant and thus may induce chemopreventive effects. However, at elevated concentrations, quercetin acts as a pro-oxidant and may, therefore, stimulate chemotherapeutic effects.
It can combat cancer via different mechanisms as depicted below:
- Induces cell cycle arrest
- Reduces proliferation
- Stimulates apoptosis and autophagy of cancer cells
- Promotes loss of cell viability
- Inhibits mitotic processes by modulating cyclins, pro-apoptotic pathways
- Prevents metastasis by reducing VEGF (Vascular Endothelial Growth Factor) secretion and MMP (Matrix Metalloproteinases) levels
- By interfering in PI3K/Akt (phosphatidylinositol 3-kinase/protein kinase B) pathway, quercetin exerts its metabolic effect on tumor cells, inhibiting key enzymes of glycolysis and glucose uptake
- Modulating MAPK/ERK (mitogen-activated protein kinase/extracellular signal-regulated kinases) molecular pathways
- Tyrosine kinase inhibition
- Regulation of mTOR (mammalian target of rapamycin) pathway
- Inhibits Akt, mTOR, and ERK phosphorylation
- Modulating Wnt/β-catenin pathway
- Reduces β-catenin and HIF-1α (Hypoxia-inducible factor-1) stabilization
- Induces caspase-3 activation
- Targets mitochondria in cancer, diminishing bioenergetics and triggering intrinsic apoptosis
Furthermore, this natural compound can potentially strengthen the impact of other chemotherapeutic medications. When used in combination with radiotherapy and chemotherapy, quercetin can guard non-cancer cells against the side effects of currently utilized cancer therapies.
Quercetin, an abundant naturally occurring flavonoid, has considerably attracted widespread attention due to its significant anticancer property. It displays remarkable chemotherapeutic and chemopreventive anti-cancer effects via different mechanisms. It is non-toxic and can adequately inhibit the growth of many types of cancer cells. Thus, for managing patients with cancer, there exists a broad application prospect for quercetin.
In humans, there is a paucity of relevant clinical evidence that quercetin can treat or prevent cancer. However, this potent flavonoid could be valuable as a low-toxicity therapeutic molecule for treating cancer and as a diet supplement (in low doses) for preventing cancer.
Along with the combination of chemotherapies and other cancer treatments, the consumption of anti-cancer foods makes a significant difference in the overall efficacy of treatment and recovery speed of cancer.
Quercetin is a boon for cancer patients and must be included in the diet for cancer patients. It is indeed a promising candidate for cancer management.
In humans, further research should evaluate the anti-cancer role of quercetin and should focus to improve the absorption, utilization ratio, bioavailability of quercetin in the human body. You can also take vitamins for cancer management, for more information, click here! Just like quercetin, lycopene and ellagic acid are also cancer-fighting food ingredients.
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