Updated: January 24, 2025

Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, and grains. Although red onions and kale are common foods containing appreciable content of quercetin, it is also found in red wine, green tea, apples, berries, Ginkgo biloba, St. John's wort, American elder, and others. Buckwheat tea has a large amount of quercetin. Quercetin is present in various kinds of honey from different plant sources. Quercetin has a bitter flavor and is used as an ingredient in dietary supplements, beverages, and foods.

Quercetin is used as a medicine most commonly taken by mouth to treat conditions of the heart and blood vessels and prevent cancer. It is also used for arthritis, bladder infections, and diabetes. However, there is limited scientific evidence to support these uses.

The antioxidant and anti-inflammatory properties of quercetin help reduce inflammation, kill cancer cells, reduce allergy symptoms, control blood sugar, and help prevent heart disease. The antioxidants in it play an important role in helping your body combat free radical damage, which is linked to chronic diseases. 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. An average person consumes 10-100 mg of it daily through various food sources as it is abundantly available in various foods. It is also available as a dietary supplement in powder and capsule form and can be taken as a dietary supplement for a variety of uses.

Dietary Sources of Quercetin

Quercetin is found naturally in many plant-based foods, particularly in the outer layer or peel. Good food sources include:

• Capers

• Peppers (yellow and green)

• Onions (red and white)

• Shallots

• Asparagus (cooked)

• Cherries

• Tomatoes

• Red apples

• Red grapes

• Broccoli

• Kale

• Red leaf lettuce

• All types of berries, such as cranberries, blueberries, and raspberries

• Tea (green and black)

The amount of quercetin in foods may depend on the conditions in which the food was grown. For example, organic tomatoes have up to 79% more quercetin than commercially grown ones.

Effectiveness

• Athletic Performance: Taking quercetin before exercise does not decrease fatigue or improve exercise ability.
• Heart Disease: While eating foods rich in quercetin, such as tea, onions, and apples, may reduce the risk of complications due to heart disease, daily quercetin supplementation shows limited impact in healthy individuals.
• Diabetes: A combination of quercetin, myricetin, and chlorogenic acid can lower blood sugar levels in diabetics, particularly when combined with metformin.
• Muscle Damage and Soreness: Quercetin may not prevent muscle soreness but could reduce damage associated with weight training.
• Upper Respiratory Infections: Supplementing with quercetin post-exercise can lower the risk of airway infections.

Side Effects and Safety

Quercetin is safe for most people when taken in short-term amounts of up to 500 mg twice daily for 12 weeks. However, excessive dosages may cause headaches, tingling, and potential kidney damage. B2B healthcare manufacturers should consider these factors when designing dosage guidelines for consumer safety.

Special Precautions and Warnings

• Avoid use during pregnancy or breastfeeding due to insufficient data.

• Individuals with kidney problems should refrain from using quercetin to avoid worsening their condition.

Interactions

Quercetin can interact with medications such as antibiotics, cyclosporine, and drugs processed by liver enzymes. To ensure safe use, B2B pharmaceutical companies must highlight these interactions in product labeling.

Healthcare Use Cases and Opportunities

Quercetin is being used in new supplement formulas to meet specific medical needs. For example, in the case of kidney transplants, combining quercetin with curcumin has been shown to help improve the organ's early functioning. This makes quercetin an important ingredient in products used during recovery after surgery.

It is also becoming popular for boosting immunity, especially after the COVID-19 pandemic. Products that mix quercetin with zinc are in demand because they support respiratory and overall immune health.

Additionally, studies have found that eating foods rich in quercetin may lower the risk of certain cancers, like lung and pancreatic cancer, especially in people who smoke. This has opened up opportunities for companies to create foods and supplements for cancer prevention.

Final Thoughts

Quercetin is a natural compound that can improve health in many ways. It can support heart health, manage blood sugar, and strengthen the immune system. This blog has shown how quercetin is found in everyday foods and is used in supplements for its many benefits.

For businesses in healthcare and pharma, quercetin provides opportunities to create new products. These can include supplements for specific conditions, foods that help boost immunity or products that aid recovery after surgeries. By focusing on sourcing high-quality quercetin and conducting proper research, companies can ensure their products are effective and trusted by customers.