Quercetin is an important medicinal component of the flavonoid family and an important dietary antioxidant. It exists in many foods, including fruits, vegetables, tea, wine, and other dietary supplements, and is beneficial to health.
Quercetin is remarkable because of its special antioxidant, anti-inflammatory, and anti-allergic effects. It is one of the best among all phytonutrients, known as a natural anti-histamine, and is also the key to making these fruits and vegetable superfoods.
What are the benefits of quercetin supplements? Are there any side effects?
Table of Contents
- What is Quercetin?
- Food sources of quercetin
- What are the benefits of quercetin?
- Are there any side effects of quercetin?
- Safety precautions
- Where to buy the most recommended quercetin capsules?
What is Quercetin?
Quercetin is classified as flavonol, one of the six subclasses of flavonoids, and is widely distributed in plants.
The name Quercetin has been used since 1857, evolved from the Latin “Quercetum”, meaning oak forest.
It has been found in research that quercetin has a variety of biological properties, including antioxidant, anti-inflammatory, antibacterial, antiviral, scavenging free radicals, and immunomodulatory activity, which form the basis of potential benefits for overall health and disease resistance.
These substances are natural pigments that evolved by plants over hundreds of millions of years. In addition to giving fruits and vegetables a multi-colored luster, the most important role is like the immune system, which is the key to plants’ resistance to external aggression and life extension.
Food sources of quercetin
Quercetin is found in a variety of foods. Vegetables include broccoli, asparagus, shallots, green peppers, tomatoes, and red lettuce. Fruits such as apples, strawberries, grapes, blueberries, cranberries, and blackcurrants.
Quercetin is also present in medicinal plants, including ginkgo, St. John’s wort, and ginseng, as well as many seeds, nuts, flowers, bark, and leaves. Green tea and wine are also considered a rich dietary source.
What are the benefits of quercetin?
1. Quercetin regulates blood pressure
According to estimates by the American Heart Association, there are currently 80 million adults in the United States suffering from essential hypertension.
Pathological factors of hypertension are largely due to increased oxidative stress, increased production of endothelin 1, decreased production of nitric oxide, and excessive stimulation of the renin-angiotensin system caused by improper control.
Treatment depends on the cause of the disease, including dietary changes (reduced sodium intake), weight loss, increased physical activity, and drug intervention.
A systematic literature review and meta-analysis (including 7 studies with a total of 587 participants) pointed out that quercetin supplementation has a blood pressure-lowering effect (mean −3.04/−2.63 mm Hg, systolic/diastolic blood pressure), And the daily dose is greater than 500 mg, and the effect is more significant than 8 weeks.
＊Conclusion: The supplementation of quercetin has the effect of regulating blood pressure, but it is limited due to insufficient samples, heterogeneity, short duration, and other issues. Large-scale research still needs to confirm the possibility of additional therapy for hypertension.
2. Quercetin helps lose weight
Overweight and obesity is a global public health problem. As a risk factor, overweight and obesity can increase cardiovascular disease, type 2 diabetes, kidney disease, arthritis, musculoskeletal problems, depression, certain cancers, Risk of insomnia, and chronic fatigue.
In addition to the well-known factors that cause obesity, such as increased intake of high-energy-density foods and decreased physical activity.
There are also several different factors, such as intestinal microbiota, endocrine disruptors, epigenetics, maternal age increase, type selection and mating, sleep debt, iatrogenic drugs, etc.
A meta-analysis of literature (including 9 randomized controlled clinical trials, a total of 525 participants) pointed out that daily supplementation of quercetin on body weight, body mass index, waist circumference ) And waist to hip ratio have no significant effect.
*Conclusion: Up to now, quercetin supplementation has not significantly helped weight loss, and there are still more long-term large-scale studies to further verify.
3. Quercetin benefits blood sugar control
Diabetes is a complex chronic disease that is associated with hyperglycemia or hyperglycemia and occurs when there is insufficient insulin secretion, insufficient activity, or both.
It is often felt that thirst, increased urine output, ketonemia, and ketosis are common symptoms of diabetes, which occur due to abnormal metabolism of carbohydrates, fats, and proteins.
A systematic literature review and meta-analysis (including 9 randomized controlled trials, a total of 781 patients with metabolic syndrome and related diseases) pointed out that quercetin supplementation does not affect fasting plasma glucose, assessment-estimation Homeostasis model of assessment-estimated insulin resistance and hemoglobin A1c levels.
However, in subgroup analysis, it was found that the effect of quercetin supplementation on fasting blood glucose reduction was ≥8 weeks and the daily dosage was ≥500 mg.
In addition, the effect of quercetin on lowering insulin concentration is most significant in subjects aged <45 years and daily dose ≥500 mg/.
*Conclusion: For patients with metabolic syndrome and related diseases, quercetin supplementation may bring positive help to blood sugar control.
4. Quercetin benefits systemic inflammation
Inflammation is the immune system’s response to harmful stimuli, such as pathogens, damaged cells, toxic compounds, or radiation, and it works by eliminating harmful stimuli and initiating the healing process. It is an important defense mechanism for the human body to maintain health.
Inflammation is characterized by redness, swelling, fever, pain, and loss of tissue function. This is caused by the response of local immunity, blood vessels, and inflammatory cells to infection or injury. Uncontrolled acute inflammation may become chronic, resulting in a variety of chronic Inflammatory disease.
A meta-analysis of literature (including 7 randomized double-blind controlled studies, a total of 549 participants) pointed out that quercetin/onion supplementation has a significant effect of reducing C-reactive protein, and especially the daily dose is greater than 500 The subjects with mg and CRP less than 3 mg/l are the most significant.
Another meta-analysis of literature (including 15 randomized controlled trials) pointed out that for participants with the disease, supplementing with quercetin has anti-inflammatory effects (which can reduce C-reactive protein and interleukin-6).
The underlying mechanism may be related to inhibition of the nuclear transcription factor-kB pathway, inhibition of leukotriene formation, interference with the AMPK/SIRT1 pathway, and promotion of nitric oxide production.
*Conclusion: The supplementation of quercetin/onion has a positive effect on the improvement of systemic inflammation. However, due to the heterogeneity between studies, more studies are needed to further confirm.
5. Quercetin regulates blood lipids
Dyslipidemia is one of the important risk factors for cardiovascular disease. According to American epidemiological data, 29% of people without clinical cardiovascular disease between 45 and 84 years old have dyslipidemia.
Studies have shown that plasma total cholesterol is reduced by 10%, the incidence of coronary artery disease is reduced by 25% after 5 years, low-density lipid cholesterol is reduced by 1 mmol/L, and cardiovascular disease mortality and non-fatal myocardial infarction are reduced by 21%.
A systematic literature review and meta-analysis (including 16 randomized, placebo-controlled trials, a total of 1575 participants with metabolic syndrome and related diseases) pointed out that quercetin supplementation can significantly reduce total cholesterol and low-density lipid Protein cholesterol and c-reactive protein levels.
In addition, quercetin does not significantly improve the levels of triglycerides, high-density lipoprotein cholesterol (HDL-C), and tumor necrosis factor-α (TNF-α).
*Conclusion: Quercetin may have a positive effect on blood lipid regulation, but due to the high heterogeneity of the included studies, more large-scale trials are still needed to corroborate.
6. Quercetin prevents upper respiratory tract infections
Acute upper respiratory infection is the most common disease in adults. It generally refers to acute nose, sinus, pharynx, middle ear, larynx, epiglottis, airway, and bronchial site infection. The common cold is the most common, generally, every year Occurs 2 to 5 times.
The common cold may be caused by various pathogenic viruses. Symptoms include mild fever, runny nose, stuffy nose, sneezing, sore throat, cough, and muscle pain.
A randomized, double-blind, placebo-controlled trial (a 12-week, 1002 participants of all ages) pointed out that, overall, supplementation of quercetin-containing compound ingredients for the incidence, severity, and The symptom score has no obvious help.
However, analysis of the same study on subjects over 40 years old (who thought they were healthy) showed that the severity and the total number of days of upper respiratory tract infection were lower in the daily dose of 1000 mg compared to the placebo group.
*Conclusion: For middle-aged and middle-aged people with good health, supplementation of quercetin may be helpful in preventing upper respiratory tract infections, but it is limited to a small number of samples and more research is still needed to corroborate it.
7. Quercetin is beneficial for allergic diseases
Allergic disease is a hypersensitivity disease in which the immune system responds to substances that are generally considered harmless in the environment. In recent decades, the prevalence of organ-specific allergic diseases such as allergic rhinitis, asthma, and eczema have been linear. rise.
In some cases, allergic diseases are quite mild, but they can also be real trouble and have a considerable impact on daily life. Serious allergic reactions can be life-threatening.
A literature review pointed out that quercetin has mast cell activation inhibition, antiviral activity, inhibits histamine release, reduces the production of pro-inflammatory cytokines, leukotrienes, inhibits the production and improvement of interleukin-4 Anti-allergic mechanisms such as Th1/Th2 balance and inhibition of antigen-specific IgE antibody formation may be helpful for the treatment or prevention of allergic diseases.
*Conclusion: Animal and in vitro studies indicate that quercetin is helpful for the prevention and treatment of allergic diseases, but human experiments are still needed to further verify
Are there any side effects of quercetin?
For most adults in good health status, quercetin is safe to use in moderation (daily dose below 1000 mg for 12 consecutive weeks), and possible side effects or adverse reactions that have been reported include nausea, headache, stomach pain, or tingling in limbs. Note 9
1. Do not use if the liver and kidney function is poor (the relevant safety is unknown).
2. Do not use for pregnant women and lactating women (the relevant safety is unknown).
3. Do not use quinolone antibiotics together, which may reduce the efficacy of drugs. The names of related drugs are Ciprofloxacin, enoxacin, norfloxacin, sparfloxacin, trovafloxacin, grepafloxacin.
4. Do not use in combination with drugs that require cytochrome P450 (cytochrome P450) enzyme metabolism, which may increase the side effects of this drug. Common related drug names are as follows:
- Cyclosporin, Paclitaxel, rosiglitazone, amiodarone, docetaxel, repaglinide, verapamil
- celecoxib, diclofenac, fluvastatin, glipizide, ibuprofen, irbesartan, losartan, phenytoin, piroxicam, tamoxifen, tolbutamide, torsemide, warfarin
- amitriptyline, codeine, flecainide, haloperidol, imipramine, metoprolol, ondansetron, paroxetine, risperidone, tramadol, venlafaxine
- lovastatin, clarithromycin, diltiazem, estrogens, indinavir, triazolam, verapamil, alfentanil, fentanyl, losartan, fluoxetine, midazolam, omeprazole), lansoprazole, propranolol, fexofenadine, citalopram, sertraline, ketoconazole, itraconazole
Where to buy the most recommended quercetin capsules?
In recent years, food safety problems in various countries have exploded, and it is not healthy but black-hearted products that everyone spends on. Therefore, European and American products with relatively strict quality control have become popular products.
And iHerb.com is a large-scale medical cosmetics e-commerce company in the United States. It has a high satisfaction rate of 97% in the evaluation of Google customers. It provides global home delivery so that you can buy it without risking buying fakes through purchasing high-quality health products.