Isoquercetin vs Quercetin vs Quercetin Phytosome 2021: What's the Difference?

Quercetin is a type of flavonoid present in many fruits, vegetables, and grains. 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 inflammation, allergy symptoms, and blood pressure.


Isoquercetin vs Quercetin

Quercetin and isoquercetin are both natural plant flavonoids. Quercetin is an aglycone, meaning that it lacks a glycoside side chain. In contrast, naturally occurring quercetin compounds are primarily glycosides, with only very small quantity occurring as an aglycone. Once absorbed from the gut, most quercetin compounds are metabolized to quercetin glucuronides, the primary metabolic form detected in plasma.

As mentioned, quercetin does not principally occur in the form in which it is available as a dietary supplement (an aglycone). Instead, it occurs mostly as quercetin glycosides. Isoquercetin is one of the naturally occurring glucosides of quercetin. Isoquercetin is also sometimes called isoquercitrin, a nearly identical quercetin-3-monoglucoside. Technically the two are different (isoquercetin has a pyranose ring whereas isoquercitrin has a furanose ring), but functionally the two molecules are indistinguishable. The literature often considers them as one and uses the names interchangeably.

Quercetin phytosome vs Quercetin dihydrate

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.

A new food-grade lecithin-based formulation of quercetin, Quercetin Phytosome, was developed and validated in healthy volunteers. Quercetin Phytosome overcomes the low bioavailability hurdle of quercetin and should help to fulfill the great health benefit potential of this flavonoid in the diet and as food supplements.

Most in vitro studies used a form of quercetin called 'quercetin aglycone'. However, this particular form of quercetin is never found in the blood, even after ingested, as it it gets changed in the liver.

According to Examine, the quercetin dihydrate form has the apparent best bioavailability followed by glycosides, aglycone, and finally rutinoside.


Quercetin Anhydrous vs Quercetin Dihydrate

Most of the quercetin ingredients on the market are in the quercetin dihydrate form. Quercetin anhydrous and dihydrate differ in the amount of water they contain. Quercetin anhydrous contains only 1% to 4% moisture and the sugar molecules that are attached to quercetin in its natural form have been extracted. This translates into 13% more quercetin per gram for quercetin anhydrous vs quercetin dihydrate. For formula manufacturers, this means there is substantially less bulk per capsule or tablet.

Frequently Asked Questions About Quercetin

This section will help to answer some of the most commonly asked questions about Quercetin.


What are the best foods for quercetin?

A: Capers, peppers (yellow and green), onions (red and white), shallots, asparagus, cherries, tomatoes, red apples, red grapes, broccoli, kale, red leaf lettuce, cranberries, blueberries, raspberries, green tea, black tea, and coffee are all excellent foods for quercetin.

Do you get enough quercetin in your daily diet?

A: The average person gets 10 to 100 mg of quercetin per day through normal dietary sources. This can vary greatly. Carefully track your diet over an extended period to figure out if you have a dietary deficiency of quercetin.

How much quercetin should you take per day?

A: Researchers typically use a dose of 500 mg of quercetin per day in supplement form. Most quercetin supplements contain between 500 and 1200 mg of quercetin, although this can vary. Check out the nutritional label for your quercetin supplement to be sure.

Does quercetin help allergies?

A: Many people take quercetin supplements to avoid allergy symptoms. There’s evidence that quercetin has powerful anti-allergy benefits, although more research needs to be done.

Q: Does quercetin fight cancer?

A: Early research in test tube and animal models shows that quercetin may have cancer-fighting properties. While these findings are promising, more large scale human studies need to be performed. Research is not definitive. Consult your physician before using any supplement to improve your cancer.

Q: Does quercetin reduce the risk of Alzheimer’s?

A: Studies show that quercetin may reduce the onset of Alzheimer’s, particularly in the early and middle stages of the condition. However, studies have mostly been performed on mice and test tubes – not in humans.

Q: What are other names for quercetin?

A: Quercetin goes by a number of different names. You might see quercetin supplements labeled as bioflavonoid concentrate, bioflavonoid extract, or citrus bioflavonoid, for example.

Q: Can quercetin help you recover after exercise?

A: Some studies show that quercetin boosts recovery after exercise. In some small studies, athletes taking quercetin after exercise had faster recovery than a control group. Researchers believe quercetin reduces oxidative stress and post-exercise inflammation, helping your body recover.

Q: What are the side effects of quercetin?

A: Most people experience no side effects from quercetin, and any side effects tend to be mild. Quercetin side effects include tingling and numbness, headache, and nausea. Your chance of experiencing side effects increases at higher dosages (over 1,000mg).

Q: Why do so many quercetin supplements contain bromelain?

A: Bromelain is a naturally occurring, protein-digesting enzyme found in the stem of the pineapple. Bromelain seems to boost the absorption of quercetin by inhibiting inflammatory chemicals called prostaglandins. Bromelain may also decrease inflammation on its own.

Your body doesn’t absorb quercetin very effectively on its own. Some studies have shown that bromelain boosts the absorption of quercetin, which is why you find bromelain (or vitamin C) in many quercetin supplements.

Q: What’s the difference between rutin or glycosidic quercetin?

A: Quercetin is found in two forms, including in rutin or glycosidic form. Quercetin glucosides, such as isoquercitrin and isoquercetin, seem to be much more bioavailable and more quickly absorbed than quercetin aglycone or quercetin glycosides, such as rutin (quercetin rutinoside).

Q: Can you overdose on quercetin?

A: In one study, researchers gave participants 2,000mg to 5,000mg of quercetin per day with no adverse effects or signs of toxicity reported. Generally, quercetin is safe to take even in high doses, although you may experience mild side effects like nausea, digestive issues, and headaches at high doses. Excessively high doses of quercetin could lead to kidney problems.

Q: How much quercetin should you take for hay fever?

A: Experts recommend taking 400mg of quercetin twice a day between meals for hay fever. Also consult your doctor to help provide a more comprehensive and effective treatment for hay fever.

Q: Can children take quercetin?

A: Most studies suggest that it’s safe to give quercetin to your child, although you should use only half the dose you'd use on an adult. Talk to your pediatrician before giving any quercetin to your child.

Q: How does quercetin manage allergy symptoms?

A: Studies have shown that quercetin stabilizes mast cells that release histamine. Histamine is the principal mediator of reactions to pollen and other allergies. This makes quercetin a natural antihistamine. Many people use quercetin to treat symptoms of hay fever, including runny nose, watering eyes, and itching.

Q: Can you take too much quercetin?

A: You should start with a quercetin dosage of around 500mg per day to assess your tolerance. However, researchers have given participants up to 5,000mg of quercetin per day with few reported side effects. Look for symptoms like upset stomach and diarrhea. Excessively high doses of quercetin could lead to kidney problems.

Q: Who should not take a quercetin supplement?


A: Quercetin appears safe for anyone to take when used in normal dosages. However, there’s limited research on how quercetin supplements affect women who are pregnant or breastfeeding. People with high blood pressure, or anyone taking blood pressure medication, may also want to take to their doctor before taking a quercetin supplement.

Q: Can you take a quercetin supplement with a pineapple allergy?

A: If you’re allergic to pineapples, you should avoid quercetin supplements with bromelain. Bromelain, an enzyme in pineapples, is added to quercetin supplements to boost bioavailability. Overuse of bromelain can create problems for consumers.

Q: Does quercetin work for anti-aging?

A: Several studies have examined the effect of quercetin on aging. Quercetin is rich with anti-inflammatories and antioxidants, which could make it a powerful anti-aging compound. 

Q: Does quercetin help asthma?

A: Quercetin may help asthma by relaxing smooth muscles lining the airway, improving airway flow.

Q: What’s better – quercetin tablets, capsules, powders, or liquid?

A: Quercetin liquid claims to be more bioavailable than other sources of quercetin. You take the liquid sublingually (underneath your tongue). However, limited research shows quercetin capsules or powders are more effective, and all forms of quercetin are absorbed poorly by the body.

Q: Where does quercetin come from?

A: Most supplement companies use various plant or vegetable-based sources of quercetin. Check the label.

Q: Can you get citrus-free quercetin?

A: Some quercetin supplements are specifically marketed as citrus-free, making them ideal for those with citrus sensitivities. Read the label or official product website for your supplement to be sure that it is actually citrus-free.

Q: Does quercetin help with diabetes?

A: There’s some evidence that quercetin helps with diabetes, helping your body manage blood sugar levels during fasting. However, more research needs to be done to verify these benefits.

Q: Is quercetin non-GMO?

A: Quercetin supplements are generally labeled non-GMO. Check the label to verify your quercetin supplement is not made from genetically modified ingredients.


Online Shopping Guide

Before adding a new supplement to your routine, discuss its use with your healthcare provider, especially if you have an underlying health condition or are taking medication.

While many of the quercetin supplements may be available in your local stores, it may be more convenient or affordable to shop for them online on Amazon (US):

  • Now Foods Quercetin with Bromelain (Amazon)

Disclaimer: The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of third party sites. If you are pregnant, nursing, taking medication, or have a medical condition, consult your health care professional before using products based on this content.


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