Onions are a staple in kitchens around the world, but their benefits go far beyond a flavoring agent. These nutrient-dense vegetables are packed with antioxidants, the most notable being quercetin. Quercetin is a powerful plant compound linked to a wide range of health benefits, from supporting immune function to promoting cardiovascular health. However, do dietary sources alone provide a therapeutic dose, or is supplementation worth considering? Let’s explore the science behind quercetin and what makes supplementation of quercetin a valuable addition to your wellness routine.
In this blog we’ll aim to answer common questions about the benefits of quercetin supplementation, including how a quercetin supplement can support health and wellness. Use the links below to jump ahead to a topic of interest.
Quercetin: Origin and Potential Applications
Quercetin is a flavonoid (a type of plant compound known for its antioxidant properties) found in various fruits and vegetables. Some of the richest sources include onions, capers, apples, berries, grapes, green leafy vegetables, and honey, as well as green and black tea. Onions contain a high amount of quercetin, with the outer layers containing the highest concentration.1
Quercetin’s unique biological properties are linked to maintaining the body’s natural inflammatory response and limiting oxidative stress to promote overall health and wellness.*
Quercetin displays antioxidant and immunomodulatory properties,*2 in addition to possessing mast cell stabilization and cytoprotective activities of the gastrointestinal tract.*4 Quercetin’s benefits are attributed to the following two primary properties of the flavonoid:
- Antioxidative properties of quercetin: Quercetin’s antioxidant properties enable it to regulate both enzyme-mediated and non-enzyme-dependent antioxidant defense systems.* Quercetin also regulates cell signaling pathways triggered by reactive oxygen species (ROS) to enhance the antioxidant defense system.*5
- Immunomodulatory properties of quercetin: Quercetin supports a healthy immune response by up-regulating beneficial immune cells, such as dendritic cells, T-helper cells, neutrophils, and microglia, making quercetin a promising botanical compound for responding to various immune-related conditions.*6,7,8,9
The following table summarizes the potential beneficial applications of quercetin:
| System | Beneficial Applications |
|---|---|
| Cardiovascular Health* |
Quercetin inhibits the oxidation of low-density lipoproteins (LDL) and helps maintain normal blood pressure levels and healthy arteries.* 10 Learn more about quercetin for heart health support.* |
| Immune Health* |
Quercetin down-regulates the release of proinflammatory cytokines and histamine, limiting adverse immune and allergic responses.* 11 Learn more about quercetin’s immune support properties.* |
| Renal Health* |
Quercetin’s antioxidant properties support the reduction of oxidative stress on the kidneys, promoting healthy kidney function.* 12 Learn more about quercetin for kidney health.* |
| Skin Health* |
Quercetin can help maintain healthy skin integrity,* which can be compromised by UV radiation and exposure to toxic chemicals by reducing oxidative stress, promoting a healthy inflammatory response, and limiting collagen degradation*. Additionally, quercetin plays a beneficial role in skin restoration by supporting skin hydration through its moisturizing effects.* 13 Learn more about quercetin’s skin benefits.* |
| Gastrointestinal Health* |
Quercetin helps maintain gut microbial diversity and a normal inflammatory response in the gastrointestinal tract.* 14 Learn more about quercetin and gut health.* |
How Does Quercetin Support Cardiovascular Health?
Oxidative stress is closely related to several cardiovascular disorders. The antioxidant and immuno-supportive properties of quercetin mitigate oxidative stress and the presence of free radicals that can damage cardiovascular tissues.* The following table summarizes how quercetin benefits heart health:*
| Quercetin and Heart Health* | |
|---|---|
| Inhibiting Oxidation of Low-Density Lipoprotein (LDL)* | Quercetin inhibits oxidative damage to LDL by down-regulating cell signaling pathways, particularly the TLR-NF-κB pathway.* 15 |
| Helping Maintain Normal Blood Pressure* | A meta-analysis found that quercetin supplementation (500 mg or more daily) helped those with high blood pressure maintain healthier blood pressure levels.* 16 |
| Inhibiting Expression of Adhesion Molecules* | Quercetin down-regulates the expression of specific cell surface proteins called adhesion molecules in aortic endothelial cells to help maintain healthy arteries.* 17 |
| Maintaining a Normal Inflammatory Response in Adipocytes and Support Healthy Glucose Metabolism* | Quercetin helps maintain a normal inflammatory response in adipocytes and promotes healthy glucose and insulin metabolism, thus supporting cardiovascular health.* 18 |
Quercetin Supports Healthy Immune Function
Quercetin alters several cell signaling pathways to down-regulate adverse allergic reactions and help maintain normal inflammatory responses.* The following table highlights how quercetin supports healthy immune function and strengthens the body’s natural defense mechanisms:*
| Quercetin and Immune Function | |
|---|---|
| Supporting a healthy histamine response: Quercetin promotes beneficial stabilization of mast cells, which release histamine — a signaling chemical involved in local allergic and immune response communication.* 19 | |
| Inhibiting proinflammatory cytokine production: Quercetin down-regulates cell signaling pathways (NF-κβ1 and Iκβ), resulting in inhibited production of proinflammatory cytokines and promoting a healthy inflammatory response.* 20 | |
| Inhibiting the production of leukotrienes: Quercetin is a potent inhibitor of leukotrienes — the biochemical mediators produced in white blood cells that cause adverse immune responses, such as the tightening of airway muscles.* 21 | |
| Enhancing Th1/Th2 balance: Quercetin promotes the balance between the two types of T-helper (Th) cells — Th1 and Th2 cells — promoting a healthy adaptive immune response.* 22 | |
| Down-regulation of antigen-specific IgE antibody formation: Quercetin inhibits the formation of immunoglobulin E (IgE) antibodies that trigger antigen-specific allergic reactions.* 23 |
Quercetin and Healthy Aging
The following table highlights several mechanisms through which quercetin promotes healthy aging:
| Quercetin Supports Healthy Aging* | |
|---|---|
| Limiting bone mass and bone mineral loss Quercetin upregulates bone mineralization to promote bone health and limit bone loss.* | |
| Upregulating SIRT1 cell signaling pathway The SIRT1 protein signaling pathway promotes healthy mitochondrial function. Research 1 indicates quercetin targets SIRT1 to upregulate multiple beneficial aging-related cellular processes.* | |
| Mitigating the effects of aging Senescence-associated secretory phenotype (SASP) — a set of characteristics displayed by aging (senescent) cells, including the secretion of high levels of inflammatory cytokines, growth factors, immune modulators, and proteases. Quercetin limits the expression of senescent cell markers and inhibits the production of SASP.* | |
| Exerting benefits on the central nervous system It has been found 2 that quercetin protects against age-related neurodegeneration.* Quercetin regulates the SIRT1/Nrf2/HO-1 cell signaling pathway, which counteracts and limits oxidative stress-mediated neuronal death 3.* | |
| Limiting glutathione depletion Quercetin enhances the activity of superoxide dismutase and catalase, thereby beneficially inhibiting glutathione depletion.* By helping to maintain mitochondrial glutathione levels, quercetin protects against free radical damage to multiple cellular components.* | |
| Addressing immunosenescence Quercetin has a direct beneficial effect on up-regulating the positive functions of multiple immune cells, including inhibiting histamine and serotonin release from intestinal mast cells.* The role of quercetin in enhancing immune resilience helps promote healthy aging. | |
| Inhibiting the activity of NF-κB signaling pathway Quercetin inhibits 4 the activity of the NF-κB signaling pathway, which protects cardiac tissues from damage caused by free radicals.* | |
Factors Affecting Quercetin’s Absorption in the Body
Post-ingestion, quercetin undergoes a process called deglycosylation and is then absorbed by the small intestine.24 Post-absorption, quercetin is metabolized in various organs, primarily the small intestine and then the liver. Quercetin and its metabolites are finally excreted mainly through the urine.
Historically, quercetin supplements have shown poor absorbability and, therefore, have decreased bioavailability.25 The key factors limiting quercetin’s absorption and bioavailability in the body are:
- Low Aqueous Solubility (does not dissolve well in water)
- Poor Permeability (does not easily pass through the intestinal barrier)
- Short Biological Half-Life (quick elimination from the body)
- Instability in the stomach and intestine (easily broken down by stomach acid and other digestive substances before reaching systemic circulation)
- Extensive First-Pass Metabolism in the Liver (rapid biotransformation into other molecules before reaching systemic circulation)
Quercetin Supplement Formulations
Quercetin accounts for up to 75 percent of an individual’s daily estimated flavonoid intake, ranging from 50 – 800 mg/day.26 Quercetin’s daily intake through food sources primarily depends on consuming fruits, vegetables, and tea. So, even if 10 – 100 mg of quercetin is consumed daily through different food sources, a supplement formulation can fill nutritional gaps to help achieve quercetin’s many health-promoting benefits.*
Commercially formulated quercetin supplements are available in oral (tablet, capsule, powder), intravenous (injectable formulations), intranasal (spray, nasal drops), and topical (ointments, gels, sprays) formats. A quercetin capsule or tablet typically contains 400 – 600 mg of the active nutrient.
Novel Formulations
Novel supplement formulations that have innovative delivery systems can overcome quercetin’s absorbability and bioavailability challenges27*. The following benefits of nano-formulated molecules enhance the overall efficacy of quercetin supplement absorption:
- Nanoformulated molecules achieve a larger surface area per molecule than their raw material counterparts.
- Such molecules can be customized for targeted delivery to the desired part of the intestine, protecting the molecules from early degradation and promoting their optimal absorption.
- Nanoformulated nutrient delivery also enables the controlled release of quercetin molecules at the desired point in the intestinal tract.
FAQs: Frequently Asked Questions About Quercetin Supplement Benefits
Are there side effects to taking a quercetin supplement?
There is no significant reported toxicity or side effects of quercetin, and its intake as a nutritional supplement at one gram daily is generally considered safe. However, there is limited data on the prolonged usage of quercetin at or above one gram daily for longer than 12 weeks.28 Ingesting too high an amount of quercetin can cause unwanted effects, such as depletion of intracellular glutathione content.28
The complexity of potential interactions of prolonged quercetin intake dictates that quercetin use as a supplement should begin only after medical consultation.
Can I take a quercetin supplement with a prescription medicine?
Quercetin can interact with certain prescription medications by reducing their absorption and effectiveness and raising the risk of side effects. Consult a healthcare practitioner to be informed about potential interactions and contraindications before initiating quercetin supplementation.
How do I determine the efficacy of a quercetin supplement?
The best indication of the efficacy of a quercetin supplement lies in the enhanced absorption and bioaccessibility of the active nutrient molecules.
QuerciSorb QR® — innovative quercetin supplement formulations developed by Tesseract Medical Research in a quick-release or sustained-release format incorporate a proprietary nanomolecular nutrient delivery technology (CyLoc® – DexKey®) that enhances quercetin’s solubility and absorption.
QuerciSorb Immuphore SR® contains quercetin, as well as additional immune-supporting ingredients, including vitamins C and D and zinc, to promote healthy immune function.*
Tesseract’s proprietary CyLoc® – DexKey® nutrient delivery nanotechnology further enhances the absorption of quercetin molecules at the desired point in the intestinal tract. The unprecedented absorption unlocks quercetin’s many health-promoting benefits, including supporting optimal cardiovascular health and immune function.*
The power of Tesseract supplements lies in enhancing palatability, maximizing solubility, absorption and bioavailability, and micro-dosing multiple nutrients in a single, highly effective capsule. Shop products on our website and learn more about how they can support your cardiovascular health and immune function.*
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