Die Wirksamkeit von Quercetin
Quercetin is classified as a flavonol, one of six subclasses of flavonoids that are widely distributed in plants.
The name quercetin has been used since 1857 and evolved from the Latin “Quercetum”, which means oak forest.
Quercetin has been found in studies to have a variety of biological properties, including antioxidant, anti-inflammatory, antibacterial, antiviral, free radical scavenging, and immunomodulatory activities, which constitute potential benefits for overall health and disease resistance.
These substances are natural pigments evolved by plants over hundreds of millions of years. In addition to giving fruits and vegetables a variety of colors, their most important role is like the immune system, which is the key for plants to resist external aggression and extend their lives.
Quercetin is found in a variety of foods, including vegetables such as broccoli, asparagus, shallots, bell peppers, tomatoes, and red lettuce, and fruits such as apples, strawberries, grapes, blueberries, cranberries, and blackcurrants.
Quercetin is also found in medicinal plants, including ginkgo, Hypericum perforatum, and ginseng, as well as in many seeds, nuts, flowers, bark, and leaves. Green tea and wine are also considered rich dietary sources.
Was sind die empirischen Auswirkungen von Quercetin?
Quercetin benefits seasonal allergies
Seasonal allergies (hay fever) are allergic reactions to airborne pollen that affect the upper respiratory tract. Nasal manifestations include congestion, runny nose, itching, and sneezing, and ocular manifestations include tearing, itching, burning, conjunctival hyperemia, and sometimes periorbital edema. The medical term for the symptoms it causes is allergic rhinitis, which is estimated to , 10%-30% of the world’s population suffers from allergic rhinitis.
The prevalence of seasonal allergies has increased rapidly over the past 50 years, with the median prevalence of allergy to grass pollen (mainly timothy) at 16.9%, second only to allergy to house dust mites at 21.7%
A four-week, randomized, double-blind, controlled trial of 66 adults with seasonal allergy symptoms found that a supplement containing quercetin (200 mg daily) improved symptoms compared with placebo. Japanese Rhinoconjunctivitis Quality of Life Questionnaire (JRQLQ) total score (a combination of quality of life and nasal allergy symptom scores, total quality of life score, sleep score, and physical score).
For seasonal allergy symptoms caused by pollen, oral supplements containing quercetin may provide positive help
Quercetin assists COVID-19 disease treatment
Coronavirus disease 2019 (COVID-19) is a new viral infection caused by SARS-CoV-2 and was declared a global pandemic by the World Health Organization on March 11, 2020
Mild COVID-19 can present with high fever, persistent cough, and loss or changes in the sense of smell/taste. However, more severe and critical cases can lead to lung inflammation, low oxygen levels and acute respiratory distress syndrome.
A randomized, controlled, open-label study (30 days of 152 outpatients with COVID-19) found that quercetin (at a daily dose of 1,000 mg), when used in conjunction with standard treatment during the early stages of viral infection, may help To improve clinical outcomes, including: reducing the need and length of hospitalization, need for non-invasive oxygen therapy, intensive care unit progression, and death.
For COVID-19 infection, quercetin combined with standard treatment may help improve early symptoms and help reduce the severity of COVID-19 disease, but due to the small sample size, more large-scale studies are still needed for further verification.
Quercetin improves aerobic exercise performance
Physical inactivity is a widespread problem worldwide, with approximately two-thirds of adults not meeting the minimum recommended physical activity
Exercise training, such as aerobic exercise, not only promotes an individual’s physical health but may also affect psychological well-being.Since physical and mental states are often interdependent, decreased physical abilities may lead to decreased self-esteem
Multiple studies report that regular and moderate exercise training can reduce the risk of cancer, heart disease, diabetes, osteoporosis, obesity, anxiety and depression
A meta-analysis of the literature (including 7 randomized, double-blind, placebo-controlled trials with a total of 288 participants) pointed out that quercetin did not significantly help improve aerobic exercise performance (in terms of endurance performance and maximum oxygen consumption). (measured by VO2max).
*Conclusion: There is limited evidence so far that oral quercetin does not improve aerobic exercise performance.
Quercetin regulates blood pressure
The American Heart Association estimates that 80 million adults in the United States currently have essential hypertension.
The pathological factors of hypertension are largely due to improper fluid control caused by increased oxidative stress, increased endothelin-1 production, decreased nitric oxide production, and overstimulation of the renin-angiotensin system.
Treatment depends on the cause of the disease and includes dietary changes (reducing sodium intake), weight loss, increased physical activity, and pharmacological intervention.
A systematic literature review and meta-analysis (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 blood pressure/diastolic blood pressure ), and the effect is most significant when the daily dose is greater than 500 mg and the use period is greater than 8 weeks.
Quercetin supplementation has the effect of regulating blood pressure, but it is limited by insufficient sample size, heterogeneity, and too short a period. Large studies are still needed to confirm the possibility of using it as an additional treatment for hypertension.
Quercetin helps with weight loss
Overweight and obesity are a global public health problem and, as a risk factor, increase the risk of cardiovascular disease, type 2 diabetes, kidney disease, arthritis, musculoskeletal problems, depression, certain cancers, insomnia, and chronic fatigue. risk
In addition to the well-known factors that contribute to obesity, such as increased intake of energy-dense foods and reduced physical activity
There are also several different factors present, such as: gut microbiota, endocrine disruptors, epigenetics, increasing maternal age, assortative mating, sleep debt, drug iatrogenicity, etc.
A meta-analysis of the literature (including 9 randomized controlled clinical trials with a total of 525 participants) reported that daily supplementation of quercetin had no significant effect on body weight, body mass index, waist circumference, and waist-to-hip ratio.
So far, quercetin supplementation has not significantly helped weight loss, and more long-term large-scale studies are still needed to further verify it.
Quercetin benefits blood sugar control
Diabetes is a complex, chronic disease associated with hyperglycemia, or a hyperglycemic state, that occurs due to insufficient insulin secretion, inactivity, or both.
Frequent feelings of thirst, increased urine output, ketonemia, and ketonuria are common symptoms of diabetes, which occur due to abnormalities in carbohydrate, fat, and protein metabolism.
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 did not affect fasting blood glucose, assessment-estimation of insulin resistance stability. state model and glycosylated hemoglobin levels.
However, subgroup analysis found that the effect of quercetin supplementation on reducing fasting blood glucose was most significant in studies involving ≥8 weeks and daily dosage ≥500 mg.
In addition, the insulin concentration-lowering effect of quercetin is most significant in subjects aged <45 years old and with a daily dose of ≥500 mg/day.
For patients with metabolic syndrome and related diseases, quercetin supplementation may have positive effects on blood sugar control.
Quercetin Benefits Systemic Inflammatory Conditions
Inflammation is the immune system’s response to harmful stimuli, such as pathogens, damaged cells, toxic compounds, or radiation, and works by eliminating harmful stimuli and initiating the healing process. It is an important defense mechanism for the body to maintain health.
Inflammation is characterized by redness, swelling, heat, pain, and loss of tissue function and is caused by local immune, vascular, and inflammatory cell responses to infection or injury. Uncontrolled acute inflammation can become chronic, leading to multiple chronic inflammatory disease
A comprehensive analysis of the literature (including 7 randomized double-blind controlled studies with a total of 549 participants) pointed out that supplementing quercetin/onionin has a significant effect on reducing C-reactive protein, especially at daily doses greater than 500 mg and CRP. Objects less than 3 mg/l are most significant.
Another meta-analysis of the literature (including 15 randomized controlled trials) pointed out that quercetin supplementation has anti-inflammatory effects (can reduce C-type reactive protein and interleukin-6) in participants with disease.
The underlying mechanism may be related to inhibiting the nuclear transcription factor kB pathway, inhibiting the formation of leukotrienes, interfering with the AMPK/SIRT1 pathway, and promoting nitric oxide production.
Supplementing quercetin/onionin can positively help improve systemic inflammation, but due to the heterogeneity between studies, more studies are needed to further confirm
Quercetin regulates blood lipids
Dyslipidemia is one of the important risk factors for cardiovascular disease. According to U.S. epidemiological data, 29% of people aged 45 to 84 without clinical cardiovascular disease have dyslipidemia.
Studies have shown that a 10% reduction in plasma total cholesterol reduces the incidence of coronary artery disease by 25% after 5 years, a 1 mmol/L reduction in low-density lipoprotein cholesterol, and a 21% reduction in cardiovascular disease mortality and non-fatal myocardial infarction.
A systematic literature review and meta-analysis (including 16 randomized, placebo-controlled trials with a total of 1575 participants with metabolic syndrome and related diseases) pointed out that quercetin supplementation can significantly reduce total cholesterol, low-density cholesterol Lipoprotein cholesterol and C-reactive protein levels.
In addition, quercetin has no significant effect on improving triglycerides, high-density lipoprotein cholesterol (HDL-C), and tumor necrosis factor-α (TNF-α) levels.
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 confirm this.
Quercetin prevents upper respiratory tract infections
Acute upper respiratory tract infection is the most common disease among adults. It generally refers to acute infection of the nose, sinus, pharynx, middle ear, larynx, epiglottis, airway, and bronchi. The common cold is the most common, usually occurring 2 to 5 times a year.
The common cold can be caused by a variety of pathogenic viruses. Symptoms include mild fever, runny and stuffy nose, sneezing, sore throat, cough and muscle pain.
A randomized, double-blind, placebo-controlled trial (12 weeks, 1,002 participants of all ages) pointed out that, overall, supplementation with a compound containing quercetin had an effect on the incidence and severity of upper respiratory tract infections. and symptom scores were not significantly helpful.
But an analysis from the same study of subjects over 40 years old (who considered themselves to be in good health) showed that the severity and total number of days of upper respiratory tract infection were lower in the 1,000 mg daily dose group compared with the placebo group.
For middle-aged and middle-aged people in good health, supplementing quercetin may be helpful in preventing upper respiratory tract infections, but due to the small sample size, more research is needed to confirm it.
Quercetin benefits allergic diseases
Allergic disease is a hypersensitive disorder in which the immune system reacts to substances in the environment that are generally considered harmless. In recent decades, the prevalence of organ-specific allergic diseases such as allergic rhinitis, asthma, and eczema has increased. Straight up.
In some cases, allergic disease is quite mild, but it can also be a real nuisance and have a considerable impact on daily life, and severe 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 and leukotrienes, inhibits the production of interleukin IL-4, and improves Th1/Th2 Anti-allergic mechanisms such as balancing and inhibiting the formation of antigen-specific IgE antibodies may be helpful in the treatment or prevention of allergic diseases.
Animal and in vitro studies indicate that quercetin is helpful in the prevention and treatment of allergic diseases, but further verification in human experiments is needed.
