What Vegetables Have Quercetin. Quercetin is a type of flavonoid found in plants such as apples, onions, kale, peppers, and garlic. It is a very popular supplement that many believe can help with weight loss and lowering cholesterol. It is also thought to be an anti-inflammatory agent that can help with allergies. Quercetin is a very popular plant supplement. Here are some of the health benefits of Quercetin .
21 Quercetin-Rich Foods That Belong In Your Diet + The Benefits Of This Antioxidant
Lindsay Boyers is a nutrition consultant specializing in elimination diets, gut health, and food sensitivities. Lindsay earned a degree in food & nutrition from Framingham State University, and she holds a Certificate in Holistic Nutrition Consulting from the American College of Healthcare Sciences.
The year 2020 cast a spotlight on immunity. As such, there was lots of discussion around the usual players, like vitamin C, zinc, and vitamin D, but another, lesser-known compound, called quercetin, also came into the light.
Like vitamins and minerals, quercetin is found naturally in many of the foods you’re probably already eating—and some that likely don’t make it to your plate very often. Here, we break down some must-knows about this potent antioxidant and share the foods highest in quercetin that deserve a place in your diet this year.
What is quercetin?
Quercetin belongs to a group of plant compounds called flavonoids. Like all flavonoids, quercetin acts as an antioxidant in your body and scavenges for free radicals. It also helps shut off inflammation, which causes oxidative damage and can contribute to a host of health problems, including cancer, heart disease, and Alzheimer’s disease, to name a few.
Research has also connected quercetin to allergy-relief and some pretty serious immune support. According to Vincent Pedre, M.D., board-certified internist, part of the reason quercetin supports your immune system is because it acts as a prebiotic, feeding the good bugs in your gut.
“It also augments the effects of vitamin C, synergistically helping to prevent over-activation of mast cells, which secrete histamine when the body is inflamed,” Pedre previously told mbg. “Not to mention, quercetin acts as a zinc shuttle, getting natural antiviral zinc into cells where it can help mitigate viral replication.”
OK, so how much quercetin do I need per day?
Quercetin is widely distributed among plant foods, like fruits, vegetables, nuts, and seeds. It’s also a component of some medicinal herbs, including Ginkgo biloba, St. John’s wort, and Sambucus canadensis, a type of elderberry.
On average, people get around 5 to 40 milligrams of quercetin per day through their diet, but if you eat a lot of fruits and vegetables, it’s likely that you’re getting closer to 200 to 500 milligrams. There’s no magical number for how much quercetin you should be getting daily, but most supplements recommend dosages between 500 and 1,000 milligrams per day—and that’s the dosage many studies on quercetin’s benefits mention, too
Foods high in quercetin.
There are quercetin supplements available, but you can also increase your intake through whole foods, which also provide additional phytochemicals, vitamins, and minerals that work synergistically to offer bonus benefits.
If you’re trying to level-up your quercetin, focus on getting a variety of these foods daily:
- capers (most concentrated source!)
- red onion (highest vegetable source!)
- red apples
- tomatoes (organically grown tomatoes have up to 79% more than conventional fruit)
Healthy Foods High in Quercetin
Quercetin is a pigment that adds color to many fruits and vegetables. It’s found mainly in the skins and leaves of plants. Light stimulates the production of quercetin, so an apple at the top of a tree may have more quercetin than one that doesn’t get direct sunlight.
Quercetin may be referred to as a phytochemical, polyphenol, or flavonoid. Phytochemicals are substances produced by plants that may have health benefits for humans. Polyphenols and flavonoids are types of phytochemicals.
Quercetin is a powerful antioxidant. Antioxidants help fight free radicals, which are molecules that contain unpaired electrons. Because electrons naturally want to pair up, free radicals roam around the body, pulling electrons away from other molecules. This process can damage cells and DNA. Quercetin “cleans up” free radicals by pairing with their single electrons so they can no longer cause damage.
Dietary intakes of quercetin in the U.S. have been reported to be around 6-18 milligrams (mg) per day. However, if you’re eating several servings of fruits and vegetables on a daily basis, you’re likely consuming much more quercetin.
Why You Need Quercetin
Research shows that quercetin has many health benefits, including:
Quercetin has been shown to support the cardiovascular system by lowering blood pressure and cholesterol and relaxing blood vessels. Because reduced blood flow can cause erectile dysfunction, flavonoids like quercetin can also improve men’s sexual health.
Improved circulation improves brain health as well. But quercetin can protect the brain in other ways, too. It may reduce inflammation and protect brain cells from toxins. Its antioxidant powers could lower the risk of Alzheimer’s disease and other degenerative diseases of the brain.
Anti- C ancer Effects
When free radicals damage cells in the body, those cells sometimes develop into cancer. Quercetin and other antioxidants reduce the risk of cancer by combating free radicals. A few studies have targeted quercetin particularly. In one, it slowed tumor growth. In another, it lowered the risk of lung cancer. The third was a lab study, which found that quercetin had the ability to attack leukemia cells.
What Is Quercetin? Benefits, Foods, Dosage, and Side Effects
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Quercetin is a natural pigment present in many:
It’s one of the most abundant antioxidants in the diet and plays an important role in helping your body combat free radical damage, which is linked to chronic diseases.
In addition, its antioxidant properties may help reduce:
- allergy symptoms
- blood pressure
This article explores quercetin’s:
- side effects
What is quercetin?
Quercetin is a pigment that belongs to a group of plant compounds called flavonoids.
Flavonoids are present in:
They’ve been linked to several health benefits, including reduced risks of heart disease, cancer, and degenerative brain disorders
The beneficial effects of flavonoids like quercetin come from their ability to function as antioxidants inside your body
Antioxidants are compounds that can bind to and neutralize free radicals.
Free radicals are unstable molecules that may cause cellular damage when their levels become too high.
Damage caused by free radicals has been linked to numerous chronic conditions, including cancer, heart disease, and diabetes
Quercetin is the most abundant flavonoid in the diet. It’s estimated that the average person consumes 10–100 mg of it daily through various food sources.
Foods that commonly contain quercetin include onions, apples, grapes, berries, broccoli, citrus fruits, cherries, green tea, coffee, red wine, and capers
It’s also available as a dietary supplement in powder and capsule form.
People take this supplement for several reasons, including to:
- boost immunity
- fight inflammation
- combat allergies
- aid exercise performance
- maintain general health
Quercetin is a plant pigment with potent antioxidant properties. It’s present in many common foods, such as onions, apples, grapes, and berries.
It can also be purchased as a dietary supplement for a variety of uses.
Health benefits of quercetin
Research has linked quercetin’s antioxidant properties to various potential health benefits.
Here are some of its top science-based benefits.
May reduce inflammation
Free radicals may do more than simply damage your cells.
Research shows that high levels of free radicals may help activate genes that promote inflammation. Thus, high levels of free radicals may lead to an increased inflammatory response
While a little inflammation is necessary to help your body heal and fight infections, persistent inflammation is linked to health problems, including certain cancers, as well as heart and kidney diseases
Studies show that quercetin may help reduce inflammation.
In test-tube studies, quercetin reduced markers of inflammation in human cells, including the molecules tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6)
An 8-week study in 50 women with rheumatoid arthritis observed that participants who took 500 mg of quercetin experienced significantly reduced early morning stiffness, morning pain, and after-activity pain
They also had reduced markers of inflammation, such as TNFα, compared to those who received a placebo
While these findings are promising, more human research is needed to understand the compound’s potential anti-inflammatory properties.
May ease allergy symptoms
Quercetin’s potential anti-inflammatory properties may provide allergy symptom relief.
Test-tube and animal studies found that it may block enzymes involved in inflammation and suppress inflammation-promoting chemicals, such as histamine
For example, one study showed that taking quercetin supplements suppressed peanut-related anaphylactic reactions in mice
Still, it’s unclear whether the compound has the same effect on allergies in humans, so more research is needed before it can be recommended as an alternative treatment.
May have anticancer effects
Because quercetin has antioxidant properties, it may have cancer-fighting properties
In a review of test-tube and animal studies, quercetin was found to suppress cell growth and induce cell death in prostate cancer cells
Other test-tube and animal studies observed that the compound had similar effects in liver, lung, breast, bladder, blood, colon, ovarian, lymphoid, and adrenal cancer cells
Though these findings are promising, human studies are needed before quercetin can be recommended as an alternative treatment for cancer.
May lower your risk of chronic brain disorders
Research suggests that quercetin’s antioxidant properties may help protect against degenerative brain disorders, such as Alzheimer’s disease and dementia
In one study, mice with Alzheimer’s disease received quercetin injections every 2 days for 3 months.
By the end of the study, the injections had reversed several markers of Alzheimer’s, and the mice performed much better on learning tests
In another study, a quercetin-rich diet reduced markers of Alzheimer’s disease and improved brain function in mice at the early middle stage of the condition.
However, the diet had little to no effect on animals with middle-late stage Alzheimer’s
Coffee is a popular beverage that has been linked to a lower risk of Alzheimer’s disease.
In fact, research shows that quercetin, not caffeine, is the primary compound in coffee that’s responsible for its potential protective effects against this illness
Though these findings are promising, more research in humans is needed.
May reduce blood pressure
High blood pressure affects 1 in 3 American adults. It raises your risk of heart disease — the leading cause of death in the United States
Research suggests that quercetin may help reduce blood pressure levels. In test-tube studies, the compound appeared to have a relaxing effect on blood vessels
When mice with high blood pressure were given quercetin daily for 5 weeks, their systolic and diastolic blood pressure values (the upper and lower numbers) decreased by an average of 18% and 23%, respectively
Similarly, a review of 9 human studies in 580 people found that taking more than 500 mg of quercetin in supplement form daily reduced systolic and diastolic blood pressure by an average of 5.8 mm Hg and 2.6 mm Hg, respectively
Although these findings are promising, more human studies are needed to determine whether the compound could be an alternative therapy for high blood pressure levels.
Other potential benefits
Here are several other potential benefits of quercetin:
- May help combat aging. Test-tube and animal research suggests that quercetin may help rejuvenate or eliminate aging cells and reduce markers of aging. However, more human research is needed
- May aid exercise performance. A review of 11 human studies found that taking quercetin may slightly improve endurance exercise performance
- May aid blood sugar control. Human and animal research indicates that the compound may reduce fasting blood sugar levels and protect against complications of diabetes
Quercetin may improve inflammation, blood pressure, exercise performance, and blood sugar management.
In addition, it may have brain-protective, anti-allergy and anticancer properties. Still, more research in humans is needed.
Food sources and dosage
Quercetin is found naturally in many plant-based foods, particularly in the outer layer or peel .
Good food sources include
- peppers — yellow and green
- onions — red and white
- asparagus — cooked
- red apples
- red grapes
- red leaf lettuce
- berries — all types, such as cranberries, blueberries, and raspberries
- tea — green and black
Note that the amount of quercetin in foods may depend on the conditions in which the food was grown.
For example, in one study, organic tomatoes appear to have up to 79% more quercetin than conventionally grown ones
However, other studies point out differences between the quercetin content in various species of tomatoes regardless of the farming method. There was no difference in bell peppers, conventionally or organically grown
You can purchase quercetin as a dietary supplement online and from health food stores. It’s available in several forms, including capsules and powders.
Typical dosages range from 500–1,000 mg per day
On its own, quercetin has a low bioavailability, which means your body absorbs it poorly
That’s why the supplements may include other compounds, such as vitamin C or digestive enzymes like bromelain, as they may increase absorption
Additionally, some research indicates that quercetin has a synergistic effect when combined with other flavonoid supplements, such as resveratrol, genistein, and catechins
Quercetin is present in many commonly consumed foods and is available as a dietary supplement. Typical doses range from 500–1,000 mg per day.
Quercetin, a bioflavonoid available in many over-the-counter products, may have the anti-inflammatory effects of other members of this class of compounds found in fruits, vegetables, and some spices.Katske et al. (2001) administered 500 mg twice daily to 22 IC/BPS patients for 4 weeks. All but one patient had some improvement in the O’Leary-Sant symptom and problem scores and in a global assessment score. Further larger studies with placebo controls are necessary to determine efficacy.
Quercetin is a natural flavonoid found abundantly in vegetables and fruits. There is growing evidence suggesting that quercetin has therapeutic potential for the prevention and treatment of different diseases, including cardiovascular disease, cancer, and neurodegenerative disease. Mechanistically, quercetin has been shown to exert antioxidant, anti-inflammatory, and anticancer activities in a number of cellular and animal models, as well as in humans through modulating the signaling pathways and gene expression involved in these processes. This chapter focuses on experimental studies supporting the anticancer, cardioprotective, and neuroprotective effects of quercetin.
Quercetin is a dietary polyphenolic compound with potentially beneficial effects on health. Most research has focused on the antioxidant properties of quercetin, its effects on several enzyme systems, and effects on biological pathways involved in carcinogenesis, inflammation and cardiovascular diseases. Upon absorption in the small intestine, quercetin is metabolized immediately by enzymes in the epithelial cells and further metabolized by the liver. Even if the bioavailability of quercetin is now relatively well documented, data is still lacking on the association of this flavonoid in the diet with respective to absorption and metabolism. As there is increasing evidence that there is little to no free quercetin in the plasma, the effects of the glucoconjugates and not free quercetin must be further investigated. Most of the studies presented focus on the aglycone form of quercetin, so the effects of the conjugates are still unkown, although, free quercetin may be readily absorbed and not detectable. Therefore, especially in the intestinal epithelial cells where there is evidence of deglycosylation, studying the effect of free quercetin may be of greater value. Understanding the mechanism of action of quercetin and the determination of its free, and conjugated forms of quercetin in plasma and urine prior to or after supplementation seems to be an important aspect as its various biological actions seem to be dose-dependant in many of these studies we have cited in this chapter. The effects of quercetin concentration are varied with low doses (0–10 μM) resulting in chemoprevention, mid ranges (10–200 μM) resulting in mixed effects, and higher concentration (>200 μM) in pro-oxidant or potential direct therapeutic properties. From the studies presented, these lower concentrations appear to be achievable by diet, while the therapeutic concentrations might require supplementation or intravenous administration and result in little or no side effects.
The Allergic Patient
Quercetin is a bioflavonoid obtained from diverse sources, including apples, buckwheat, onions, and citrus fruits. Most data supporting the role of quercetin in attenuating allergic reactivity have been obtained from in vitro studies, as well as from animal models of allergic disease. In vitro studies have shown that quercetin stabilizes the membranes of mast cells and reduces the release of preformed histamine. In animal models, quercetin is able to suppress anaphylactic responses in sensitized rats, and it inhibits asthmatic inflammation in guinea pigs and rats.
Quercetin must be used as a preventative—taken before allergen exposure. Thus the activity of quercetin is similar to that of cromolyn, a drug that is often prescribed for allergy and asthma prophylaxis (see later). Quercetin also inhibits the production of enzymes responsible for manufacturing the potent leukotrienes. Practitioners usually recommend that quercetin be used regularly during an individual’s entire allergy season, or year-round for those with perennial allergies.
Quercetin is similar to cromolyn in its mechanism of action. Both are basophil and mast cell stabilizers.
The dose of quercetin is usually 400–600 mg of a coated tablet one to three times daily between meals (adjust dose for clinical response). Quercetin is not soluble in water, however, so it is a poorly absorbed nutrient. Bromelain, a protein-digesting enzyme extracted from pineapples, increases the absorption of quercetin, as does vitamin C. Therefore quercetin is typically sold blended with one or both additives.