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Quercetin (pronounced kwer-set-in) is highly studied for its role in numerous biological and antioxidant actions in the body. Many are interested in this supplement for its potential to reduce disease risk. Is this supplement a “must-have” or will our normal diets do?

Foods with a high quercetin content include onions, apples, berries, kale and tea. Estimates of the average consumption of quercetin vary (about 25-50 milligrams per day) and are influenced by daily intake of fruits and vegetables.

Quercetin is a type of flavonoid — a large group of natural substances called phytochemicals found in high concentrations in leaves and skins of plants (also responsible for plant pigmentation). Flavonols are the most abundant flavonoids in foods, especially quercetin (from the Latin word “quercetum” or “oak forest”).

May lower inflammation, blood pressure

Quercetin is commercially available in dietary supplements, which claim several benefits, including support for inflammation and immune health. Quercetin is able to modulate inflammation by inhibiting inflammatory enzymes. For this reason, it is studied in both animals and humans for its effects on cardiovascular disease, diabetes, certain cancers and especially hypertension.

Several studies report that quercetin supplementation (150-730mg/day) reduces blood pressure in hypertensive participants and in women with Type 2 diabetes. A 2015 randomized controlled trial of 162 mg/day of quercetin decreased 24-hour ambulatory blood pressure in hypertensive participants. However, data are not consistent for this effect, and there was no change in resting systolic blood pressure, inflammatory or cardiometabolic markers.

Safety and side effects

Data from clinical studies on oral supplementation of quercetin at doses ranging from 3-1,000mg/day for up to 12 weeks show no significant adverse effects. As a whole, the evidence supports its safety at estimated dietary intake levels.

There is limited data on the safety of longer-term or higher doses. There are reports of kidney toxicity and gastrointestinal symptoms when quercetin was intravenously administered at high doses, though these are not likely with oral supplementation. The safety of quercetin supplementation during pregnancy and lactation is not yet established.

Interactions

Supplemental flavonols, including quercetin, may interact with antibiotics, chemotherapeutics or antihypertensives. Before starting a new supplement or diet, please consult with your doctor to determine if it’s appropriate for you.

Reprinted with permission from Environmental Nutrition, a monthly publication of Belvoir Media Group, LLC, 1-800-829-5384, EnvironmentalNutrition.com.

© 2021 Belvoir Media Group. Distributed by Tribune Content Agency, LLC.