Scientists from the Hospital of Southern Medical University found that quercetin, a plant pigment (flavonoid) that gives many fruit colors may help control high blood pressure.
Quercetin is a plant pigment. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it.
It has a bitter flavor and is used as an ingredient in dietary supplements, beverages, and foods.
Previous research has found that quercetin has antioxidant and anti-inflammatory effects that might help reduce swelling, kill cancer cells, control blood sugar, and help prevent heart disease.
Recent clinical studies examining the heart-protective benefits of quercetin have reported conflicting results.
In the study, the team aimed to summarize evidence of the effects of quercetin supplementation on cholesterol, blood pressure, and blood sugar levels in humans.
They reviewed 17 clinical studies which tested 896 participants. The results showed that quercetin intake strongly lowered both systolic blood pressure and diastolic blood pressure.
Blood pressure is measured using two numbers: The first number, called systolic blood pressure, measures the pressure in your arteries when your heart beats.
The second number, called diastolic blood pressure, measures the pressure in your arteries when your heart rests between beats.
Neither cholesterol nor blood sugar levels strongly changed.
In a further analysis, the researchers found that when participants consumed quercetin for 8 weeks or more, there were big changes in high-density lipoprotein (HDL, “good”) cholesterol and triglycerides.
HDL, or “good” cholesterol, absorbs cholesterol and carries it back to the liver. The liver then flushes it from the body. High levels of HDL cholesterol can lower the risk for heart disease and stroke.
Triglycerides are a type of fat (lipid) found in the blood. When one eats food, the body converts any calories it doesn’t need to use right away into triglycerides.
The triglycerides are stored in fat cells. Later, hormones release triglycerides for energy between meals.
People who regularly eat more calories than they burn, particularly from high-carbohydrate foods, may have high triglycerides.
High triglycerides may contribute to the hardening of the arteries or the thickening of the artery walls. This can increase the risk of stroke and heart attack.
Based on these findings, the team concluded that quercetin intake can lead to strongly decreased blood pressure in humans.
Moreover, people who consumed quercetin for 8 weeks or more showed some big changes in cholesterol and blood fat levels.
One limitation of the study is that the results were from different groups of participants, i.e. healthy people as well as those with type 2 diabetes, obesity, or high blood pressure.
This makes it hard to clarify the heart-protective effect of quercetin on people with different risks of heart disease.
In addition, the 17 studies reviewed in the research had different designs, target populations, and characteristics of participants. How these factors could affect the conclusion needs future work to find out.
The research is published in Nutrition Reviews and was conducted by Haohai Huang et al.
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