Best Quercetin Supplement for Your Heart

Quercetin belongs to a category of more than 4,000 naturally available plant-derived phenolic compounds. Quercetin, among the most popular flavonoids and nutritional antioxidants, is naturally available in vegetables, fruits, tea, wine, and other food sources. Quercetin’s antioxidant and immunomodulatory properties support various health functions, including the heart, kidneys, immune function, gastrointestinal system, and skin.*   

Quercetin’s unique capability to scavenge free radicals, such as peroxynitrite and the hydroxyl radical, provides significant benefits for cardiovascular health, highlighting the need for including a quercetin supplement in your diet.* But what is the best quercetin supplement to promote the health of your heart? See the answers below to common queries about quercetin supplements, including absorption challenges, novel formulations, and the features of the best quercetin supplements. Use the links below to jump ahead to different topics on the page.

Why Should You Consider A Quercetin Supplement?

Based on your consumption of fruits, vegetables, and tea, your estimated flavonoid intake can be between 50 – 800 mg/day. Quercetin can account for up to 75 percent of your daily flavonoid intake. Then why should you consider taking a quercetin supplement?

Naturally occurring quercetin has very poor oral bioavailability (around 2%). The oral intake of 100 mg of quercetin glucoside, the naturally occurring form of quercetin, displays a bioavailability range between 3 – 17 percent in healthy individuals. Low bioavailability means less absorption of quercetin, which results in failing to achieve the desired health benefits. 

In contrast to natural quercetin, supplement formulations utilize novel nutrient delivery technologies that enhance the active nutrient’s bioavailability and absorption, making it a therapeutic reality. This is why you should consider including a quercetin supplement in your diet.    

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How Does A Quercetin Supplement Promote Cardiovascular Health? 

Oxidative stress in the body’s cardiovascular system results from insufficient antioxidant capacity to limit reactive oxygen species and free radicals. Oxidative stress is linked to various adverse heart conditions, including high blood pressure, high cholesterol, hardening of the arteries, and others. Several studies^1,2 indicate the role of antioxidants in maintaining cardiovascular health.*

The presence of the highly reactive hydroxyl groups in the chemical structure of quercetin and its existence as a conjugated molecule with carbohydrates, lipids, alcohol, and sulfate group, or in unconjugated form as an aglycone result in metabolic derivatives that remove reactive oxygen species (ROS).* The antioxidant and immunosupportive properties of quercetin exert cardioprotective effects by inhibiting cell death (apoptosis), limiting oxidative stress, and downregulating inflammatory proteins in the heart.*

The following table lists some potential positive effects of quercetin on cardiovascular health.*

Commercially Available Quercetin Supplements 

The U.S. Food and Drug Administration categorizes quercetin as a Generally Recognized as Safe (GRAS) compound for its use as a dietary supplement. Oral quercetin supplements are among the most popular, with daily dosages of 500 – 1,000 mg. The following table summarizes the types of commercially available quercetin supplements: 

Absorption Challenges of Quercetin

Not all quercetin supplements are formulated similarly, and most cannot overcome the naturally poor bioavailability and absorption of the active ingredient. So, what is it that adversely affects the absorption of quercetin supplements? Let’s look at the fate of orally ingested quercetin as it passes through the gastrointestinal tract.    

Quercetin is primarily absorbed in the upper segment of the small intestine. Quercetin metabolites, after they are released into the blood and lymphatic circulation, reach the liver and enter hepatocytes (liver cells), where they are metabolized by Phase II conjugating enzymes in various organs, including the liver, small intestine, colon, and kidney. The kidneys finally excrete quercetin and its metabolites in the urine. 

The following are the key factors adversely affecting quercetin’s absorption in the body:

• Poor Aqueous Solubility
• Instability in Physiological Medium (Stomach and Intestine)
• Poor Permeability
• Rapid degradation
• Extensive First-Pass Metabolism in the Liver

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Strategies to Enhance Quercetin’s Bioavailability

Conventional strategies to enhance the bioavailability of quercetin involve consuming foods with a higher quercetin content, particularly its glycosylated form. However, the ideal approach to enhance the solubility of quercetin requires protecting its integrity in the upper gastrointestinal tract and its subsequent release at the desired point in the gastrointestinal tract for optimal absorption.  

• Food sources with higher quercetin content. Onions, asparagus, and berries have a relatively higher concentration of quercetin than other food sources.  

• Co-administration of quercetin with dietary components. Quercetin intake with dietary fat increases its absorption through micellarization in the small intestine. 

• Differences in Glycosylation. The glycosyl group attached to quercetin’s chemical structure influences water solubility and absorption. This is why quercetin glucosides in onions or shallots are more readily absorbed than quercetin rutinosides in tea. 

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The Most Bioavailable Form of Quercetin

Quercetin is an aglycone, which means it lacks an attached sugar to its chemical structure. However, in foods and supplements, quercetin is often present in various conjugated forms,  including quercetin glycoside, quercetin sulfate, quercetin glucuronide, and methylated quercetin. These structural differences significantly impact its absorption and bioavailability. 

It is worth noting that foods with the highest concentration of quercetin are not necessarily the most bioavailable sources. In general, quercetin glycosides are generally more bioavailable than the aglycone form. For instance, the glucoside conjugates of quercetin found in onions are reported to have the highest bioavailability as they are more readily absorbed in the GI tract compared to other forms. 

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Novel Quercetin Supplement Formulations

Novel quercetin supplement formulations utilize the lipophilic property of quercetin to increase its bioavailability and subsequent absorption. The following are some common approaches used to enhance quercetin pharmacokinetics: 

1. Solid lipid nanoparticles: Quercetin is entrapped within a solid lipid nanoparticle structure to enhance cellular penetration. However, this technique has minimized loading efficiency and escape through the matrix during storage. 

2. Nanostructured lipid carriers: Nanostructured lipid carriers are efficient carriers for topical delivery of quercetin and address the drawbacks of solid lipid nanoparticles with better encapsulation efficiency. 

3. Liposomes: A liposomal delivery system solubilizes quercetin and enhances its pharmacological and pharmacokinetics properties to facilitate intracellular delivery and prolong its cell retention time. 

4. Niosomes: Niosomes offer enhanced permeability in the transdermal delivery of nutrients. Quercetin-loaded niosomes have shown good antioxidant potential. 

5. Transferosomes: Quercetin-loaded transferosomes help achieve sustained release of the active nutrient with a predictable and extended period of activity.  

6. Nanoemulsions: Nanoemulsions are more stable than liposomes. When encapsulated in nanoemulsion form, quercetin has pronounced antioxidant effects even in lesser amounts. 

7. Microemulsions:  Microemulsions offer enhanced drug solubilization, making it a promising option for oral quercetin formulations. 

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FAQs: Frequently Asked Questions About Oral Quercetin Supplements 

Are there side effects to taking a quercetin supplement?

The safety profile of quercetin is well-established at one gram per day. Although adverse side effects of quercetin have rarely been reported, limited data is available on long-term quercetin use at levels at or above one gram daily for longer than 12 weeks.

Can I take a quercetin supplement with a prescription medicine?

Quercetin might cause potential contraindications with certain prescription medications, such as blood thinners. Consult with your healthcare provider before including a quercetin supplement in your diet or taking one with a prescription medicine.  

What is the best quercetin supplement for heart health?

The key features of the best quercetin supplement are enhanced bioavailability and absorption of the active nutrient molecules. Tesseract Medical Research’s Quercisorb SR® is an innovative quercetin supplement complex that contains extracts from the flower Sophora japonica — to support your heart health.*

The proprietary CyLoc^® – DexKey^® technology is a revolutionary nutrient delivery nanotechnology that enhances the bioavailability and absorption of quercetin. The CyLoc® technology encases individual quercetin molecules in its dextrin fiber cage to maintain their integrity during their transit through the stomach. The accompanying DexKey® reactors release quercetin molecules at the desired point in the intestinal tract for unparalleled absorption. 

Optimal levels of absorption and enhanced bioavailability of each quercetin molecule enable micro-dosing to support cardiovascular function all day long.*

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Citations:

¹Leopold JA. Antioxidants . . . . Coronary artery disease vol. 26,2 (2015): 176-183. doi:10.1097/MCA.0000000000000187

²Cammisotto V, et al. The Role of Antioxidants Supplementation in Clinical Practice: Focus on Cardiovascular Risk Factors. Antioxidants (Basel). 2021;10(2):146. doi:10.3390/antiox10020146

³Kedhari-Sundaram M, et al. Quercetin modulates signaling pathways . . . .” Bioscience reports vol. 39,8 BSR20190720. 13 Aug. 2019, doi:10.1042/BSR20190720

⁴Li C, et al. Quercetin inhibits LPS-induced adhesion molecule expression and oxidant production in human aortic endothelial cells by p38-mediated Nrf2 activation and antioxidant enzyme induction. Redox biology vol. 9 (2016): 104-113. doi:10.1016/j.redox.2016.06.006