Hypertension

• In 2007 The Journal of Nutrition published a double-blind, crossover study in which 41 prehypertensive and stage 1 hypertensive subjects received either a placebo or 730 mg of quercetin per day for 28 days. Results showed quercetin produced a modest reduction in blood pressure in stage 1 hypertension individuals, compared to a placebo. [Source]

Atherosclerosis

• In 2015 Molecular Nutrition & Food Research published an in vitro study which showed that quercetin protected endothelial cells (cells that line blood vessels) from damage caused by oxidative stress. [Source]
• In 2017 Molecular Nutrition & Food Research published an animal study which showed that quercetin slowed the progression of atherosclerosis in mice. [Source]  
• In 2016 Cellular Immunology published an animal study which showed that quercetin supplementation significantly reduced atherosclerosis-related inflammatory markers in atherosclerotic rats fed a high-cholesterol diet. [Source]
• In 2014 the Journal of the International Society of Sports Nutrition published an animal study which showed that mice treated with quercetin and put on an exercise regimen had 78 percent less atherosclerosis plaque compared to a control group when both groups were fed the same atherogenic (atherosclerosis-causing) diet. [Source] 
• In 2011 Pharmacological Reports published an animal study which showed that quercetin exhibited an anti-atherogenic effect in rabbits with cholesterol-induced atherosclerosis. [Source] 
• In 2005 Pharmacological Reports published an animal study which found that quercetin supplementation reduced the formation of atherosclerotic plaque in rabbits fed a high-fat diet. [Source]
• In 2017 Food and Chemical Toxicology published an animal study in which atherosclerosis-bred mice were fed either a high-fat diet alone or combined with a quercetin supplement for 24 weeks. Results show that quercetin significantly alleviated oxidative stress and reduced arterial plaque buildup. [Source]
• In 2013 Nutrition published an animal study which found that quercetin supplemented both during a high-cholesterol diet and after a high-cholesterol diet significantly reduced various inflammatory markers related to the onset of atherosclerosis, in rabbits. [Source]
• In 2011 Atherosclerosis published a study which showed that quercetin reduced atherosclerosis progression by 40 percent in transgenic mice bred to have high rates of atherosclerosis. In addition, an in vitro trial showed that quercetin protected human endothelial cells (cells that line blood vessels) against oxidative damage – a major factor in atherosclerosis. [Source]

Asthma

• In 2007 Inflammation Research published an animal study which found that quercetin supplementation suppressed inflammation and showed potential for treating allergic asthma in mice. [Source]
• In 2013 The American Journal of Physiology Lung Cellular and Molecular Physiology published an animal study which found that quercetin acutely relaxed contracted airways in mice. [Source]

Reduced inflammation and oxidative stress

• In 2012 the Journal of Research in Medical Sciences published a 60-subject, double-blind study in which 8 weeks of supplementation with 500 mg/day quercetin + 250 mg/day vitamin C reduced oxidative stress and inflammatory biomarkers in healthy subjects more than a placebo, quercetin or vitamin C alone. [Source]
• In 2008 Metabolism published an animal study which showed that quercetin effectively reduced circulating markers of inflammation in mice fed a high-fat diet. [Source]

Prostate cancer

• In 2004 Clinical and Diagnostic Laboratory Immunology published an in vitro study which showed that quercetin significantly inhibited the growth of highly aggressive prostate cancer cells. [Source]

Arthritis

• In 2006 Inflammation Research published an in vitro study which demonstrated that curcumin and to a lesser extent quercetin may offer potential in treating rheumatoid arthritis. [Source]
• In 2015 Archives of Biochemistry and Biophysics published an animal study which found that quercetin prevented pro-inflammatory activity in various organs of arthritis-induced rats. [Source]
• In 2009 the Journal Of Medicinal Food published an animal study which found that quercetin helped to reduce inflammation in arthritic mice fed a vitamin-E depleted diet. [Source]
• In 2017 Biomedicine and Pharmacotherapy published an animal study which demonstrated that quercetin, a non toxic agent, produced better results than methotrexate for protecting joints from inflammation in arthritic mice. [Source]
• In 2006 Biochemical Pharmacology published an animal study which showed that oral administration of quercetin in arthritis-induced rats produced a measurable decline in signs of arthritis compared to an untreated control group. [Source]  

Rheumatoid arthritis

• In 2016 the Journal of the American College of Nutrition published a double-blind, placebo-controlled trial in which 50 women with rheumatoid arthritis received either 500 mg/day quercetin or a placebo for 8 weeks. Compared to the placebo group, the quercetin group saw significant improvements in a number of clinical symptoms including early morning stiffness, morning pain, pain after activity and a significant reduction in high-sensitivity tumor necrosis factor-a (TNF-a) levels – a key marker of systemic inflammation. [Source]

Reduced blood pressure in Type 2 diabetics

• In 2013 the International Journal of Preventive Medicine published a double-blind study in which 72 women with type 2 diabetes received either 500 mg/day quercetin or placebo daily for 10 weeks. Compared with a placebo, the quercetin group saw a significant reduction in systolic blood pressure. [Source]

Aphthous Ulcers (Canker sores)

• In 2010 the Journal of Contemporary Dental Practice published a study which showed that topical quercetin cream significantly deceased healing time of aphthous ulcers (canker sores), with 18 of 20 male patients seeing complete healing in 4 to 7 days. [Source]
• In 2003 Toxicology published an animal study which showed that quercetin provided a gastro-protective effect, reducing the area of gastric erosions, in ulcer-induced rats. [Source]

Eye health

• In 2015 Investigative Ophthalmology & Visual Science published an in vitro study which showed that quercetin and resveratrol both exhibited anti-inflammatory and antioxidant effects on eye cells which suggests therapeutic potential in the treatment of inflammatory ocular surface diseases (eye diseases). [Source] 

Kidney protection

• In 2010 European Review for Medical and Pharmacological Sciences published an animal study which showed that quercetin combined with vitamins C and E protected rats against induced kidney damage. [Source] 

Dry eyes

• In 2015 Cornea published an animal study which showed that topical quercetin reduced dry eye in mice through increasing tear production and reducing corneal surface irregularity and inflammation. [Source]