Quercetin Elevates Your Healthspan

Quercetin belongs to a group of plant nutrients called flavonoids, which are widely found in fruits and vegetables.¹ Studies show that the consumption of flavonoid-rich foods reduces the risk of cardiovascular diseases, metabolic disorders, non-alcoholic fatty-liver disease (NAFLD), and certain types of cancer.^{2 3} As an antioxidant, anti-histamine, anti-inflammatory, anti-aging, and anti-viral supplement, quercetin quintuples its health-promoting effect on the body and works synergistically with other key nutrients, like zinc and vitamin C, to expand our “healthspan”— the number of years we can expect to live in good health.

Our bodies cannot make quercetin, so we must obtain it from food or supplements. But food sources alone cannot supply optimal amounts of this powerful antioxidant—to achieve a dose of 500 mg, you’d have to eat 5 ½ cups of red onion or 28 cups of blueberries every day. With supplementation, you can obtain 500 mg with just one capsule.⁴ Typical doses in studies evaluating quercetin’s effectiveness range between 500 mg and 1,000 mg/day.⁵

Quercetin Is a Respiratory Rockstar

Quercetin really shines during the change of seasons and any time allergies and hay fever are at their peak. That’s because quercetin exerts an anti-allergy effect by inhibiting the release of pro-inflammatory compounds, like histamine, that cause allergy symptoms, including itching, sneezing, watery eyes, runny noses, and bronchoconstriction.^{6 7}

In a 2022 placebo-controlled, double-blind study on 66 subjects between the ages of 22 and 78 with allergic symptoms, those taking 200 mg of oral quercetin daily for four weeks saw a significant improvement versus the placebo group. According to the results, “eye itching, sneezing, nasal discharge, and sleep disorder were significantly improved in the quercetin-containing supplement group compared with the placebo group. Furthermore, the quality of life of these subjects significantly improved based on the original questionnaire and visual analog scale.”⁸

But quercetin does more than just quench an allergy attack—it is also frequently used to treat a variety of respiratory conditions, including asthma and chronic obstructive pulmonary disease (COPD).⁹ Quercetin is also beneficial for the prevention and treatment of bronchitis. It relaxes airway smooth muscle, modulates inflammation, and supports healthy respiratory function in the respiratory tract, as well as the sinuses.

Quercetin can also offset the harmful effects of air pollution caused by carbon dioxide and wildfire smoke, and even cigarette smoke.^{10 11} One in vitro study examining the effects of quercetin combined with vitamin C on bronchial cells when exposed to fine particulate matter (PM2.5), an especially dangerous type of air pollution, found that the combination of quercetin and vitamin C “strikingly” reduced PM2.5’s negative health effects to the cells, in part by reducing inflammation, oxidative damage, and mitochondrial damage.^{12 13}

Quercetin Is a Potent Antiviral

Most of us are familiar with the importance of vitamins C and D and zinc for immune health. In addition to these core supplements, quercetin is another valuable supplement to add to your immunity toolkit because it displays an impressive range of antiviral properties, including inhibiting virus entry, virus replication, and virus protein assembly.¹⁴ This helps us fight upper respiratory infections like the common cold, as well as influenza. Quercetin also alleviates infection-related symptoms through its ability to reduce the release of inflammatory cytokines, proteins released by certain immune cells as part of the immune response.^{15 16 17}

In one study, participants 40 and older had a 36 percent reduction in upper respiratory infection severity and a 31 percent reduction in total sick days when taking 1,000 mg of quercetin, plus 1,000 mg of vitamin C and 40 mg of niacin, for 12 weeks, compared to the placebo group.¹⁸

Quercetin Combats COVID-19

A 2023 meta-analysis reviewed five randomized controlled clinical trials examining quercetin’s effect on 544 COVID-19 patients. The study examined the impact of quercetin (when given alongside standard treatment) on various biomarkers of COVID-19 illness, as well as hospital and ICU admission, and mortality rates. The dose of quercetin used in the studies varied from 480 to 1,500 mg/day and the duration of supplementation ranged between one and four weeks. The form of quercetin supplement also varied with several studies using quercetin phytosome, one using pure quercetin, and one using an IV and oral quercetin combo.

Some of the biomarkers they looked at included C-reactive protein (CRP) & ferritin (markers of inflammation), and lactate dehydrogenase (LDH) enzyme (released from damaged cells, indicating tissue damage). The results showed significant reductions in LDH activity following supplementation with quercetin, implying less tissue damage. Supplementation also reduced the risk of hospitalization by 70 percent, risk of admission to the ICU by 73 percent, and mortality by 82 percent.¹⁹

Quercetin Is a No-Brainer for Healthy Brain Aging

Quercetin is one of a handful of nutrients that has the unique ability to cross the blood-brain barrier and support brain function; it scavenges free radicals, combats​ inflammation​, supports mitochondrial function and health,​ and reduces amyloid plaque formation​, a hallmark of Alzheimer’s disease.²⁰ It protects the brain from the neurotoxic effect of chemicals, neuronal injury, and neurodegenerative diseases such as Alzheimer’s.²¹ It also protects brain cells by stimulating cellular defenses against oxidative stress and reducing reactive oxygen species (ROS) in the hippocampus—a complex brain structure involved in learning and memory.²²

A 2022 study further supports quercetin’s brain health benefits—even in those without cognitive impairment. Eighty men and women aged 60–75 years old participated in a placebo-controlled, randomized trial where the experimental group regularly consumed 500 mL of a beverage containing 110 mg of quercetin as isoquercetin (also called enzymatically modified isoquercetin, or EMIQ) for 40 weeks. At the end, participants were assessed for cognitive function, cerebral blood flow, and health-related quality of life.

Results showed that from baseline to week 40, there was a significant improvement in the quercetin group compared to the placebo group in reaction time. The researchers concluded that the improvement in reaction time indicates that quercetin helped improve the ability to process information and stay focused.²³ Furthermore, by attaching an oxygen monitor to the participants’ forehead, the researchers also discovered that cerebral blood flow and volume significantly decreased in the placebo group, but not in the quercetin group. This indicates that the quercetin group maintained healthy blood flow to the brain. The researchers also suggested that the effects of quercetin on blood flow could be due to its action on supporting vascular function.²⁴

Quercetin Is a Cardiovascular and Blood Vessel Champion

Quercetin can also make your heart do a happy dance. It reduces the risk of cardiovascular disease (CVD) by lowering systolic and diastolic blood pressure and decreasing total and LDL cholesterol levels. It’s even been suggested to be a key component in the cardiovascular-protective element of eating the Mediterranean diet, which is associated with a decrease in cardiovascular diseases on the whole.²⁵

In one double-blind, placebo-controlled study, 93 overweight or obese subjects aged 25–65 with metabolic syndrome were randomly selected to receive 150 mg of quercetin or a placebo for six weeks. In contrast to the placebo group, quercetin decreased systolic blood pressure in all subgroups, including hypertensive subjects, and in the subgroup of younger adults aged 25–50 years.²⁶ Quercetin also significantly decreased plasma concentrations of LDL cholesterol in the overweight subjects with high CVD risk factors.²⁷

Quercetin combats CVD in another key way. Atherosclerosis is the disease of the arteries characterized by the buildup of cholesterol plaques on their inner walls, thereby obstructing blood flow.²⁸ In a study examining aortic samples with atherosclerotic disease, when quercetin was applied to the affected samples, the flavonoid specifically accumulated in the injured aorta. These observations suggest that quercetin exerts anti-atherosclerotic activities, including the inhibition of foam cell formation in the aorta, which is known to progress to atherosclerosis.^{29 30}

Quercetin, PCOS, & Fertility

It is estimated that five to six million women suffer from Polycystic Ovary Syndrome (PCOS), the most common cause of infertility.³¹ Women with PCOS tend to have reduced total antioxidant levels and higher oxidative stress. Enter in the “queue” quercetin, whose unique constituents have been shown to decrease inflammation, balance hormone function, and improve pregnancy outcomes in those suffering from PCOS. A 2023 randomized clinical study sought to discover if quercetin could be beneficial in improving hormone parameters and pregnancy outcomes in PCOS patients. In the study, 72 women diagnosed with PCOS were either given 500 mg of quercetin per day for 40 days or a placebo. Those in the quercetin group saw an improvement in the health of the oocyte (immature egg cell), embryo grade, and overall pregnancy rate. Hormone levels—including what’s known as the luteinizing hormone (LH), impacting follicular growth, egg maturation, and ovulation—were all improved in those taking quercetin.³² The study concluded, “Regular consumption of quercetin has been shown to decrease inflammatory and LH parameters, making it beneficial for the management of PCOS and related diseases.”³³

With its wide-ranging, whole-body implications, quercetin has the power to unlock a wealth of health benefits!

Learn More About Why We Think Quercetin Is a Nutrient You Should Know About

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References

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