Scientists from the Hospital of Southern Medical University have found that quercetin—a plant pigment (flavonoid) that gives many fruits and vegetables their color—may help lower high blood pressure.
Quercetin is naturally present in a wide range of foods, including capers, red onions, and kale, as well as many fruits, vegetables, leaves, seeds, and grains.
It has a slightly bitter taste and is often used in dietary supplements, beverages, and foods.
Previous studies have shown that quercetin has antioxidant and anti-inflammatory properties. These effects may help reduce swelling, fight cancer cells, control blood sugar, and lower the risk of heart disease. However, clinical research on quercetin’s heart-protective benefits has produced mixed results.
In this study, researchers reviewed 17 clinical trials involving 896 participants to evaluate the effects of quercetin supplements on cholesterol, blood pressure, and blood sugar levels.
Their analysis showed that quercetin intake significantly reduced both systolic and diastolic blood pressure:
- Systolic blood pressure measures the pressure in the arteries when the heart beats.
- Diastolic blood pressure measures the pressure in the arteries between beats.
However, quercetin did not produce strong changes in overall cholesterol or blood sugar levels.
When the researchers performed a deeper analysis, they found that participants who took quercetin for 8 weeks or longer experienced notable improvements in high-density lipoprotein (HDL) cholesterol—the “good” cholesterol—and triglycerides, a type of fat found in the blood.
HDL cholesterol helps carry cholesterol back to the liver, where it can be removed from the body. Higher HDL levels are linked to a lower risk of heart disease and stroke.
Triglycerides store unused calories and provide energy between meals. Consistently high triglyceride levels can contribute to the hardening or thickening of artery walls, increasing the risk of heart attack and stroke.
Based on these findings, the researchers concluded that quercetin supplementation can strongly reduce blood pressure in humans, with longer-term use (8+ weeks) offering additional potential benefits for HDL cholesterol and triglycerides.
However, the team also noted some limitations. The studies involved different types of participants, including healthy individuals and those with obesity, high blood pressure, or type 2 diabetes. Because of this, it is difficult to determine how quercetin affects people with varying levels of heart-disease risk.
Additionally, the 17 studies differed in design, participant characteristics, and methods, making it challenging to draw firm conclusions. More research is needed to clarify how quercetin works and who may benefit from it the most.
The findings were published in Nutrition Reviews and conducted by Haohai Huang and colleagues.
