Quercetin in Food as Compared to Supplementation

// Lauren Martin, MS, CNS

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Quercetin in Food as Compared to Supplementation

Flavonoids are continuing to receive an ample amount of attention for their biological activities. Due to this attention, quercetin, one of the most abundant flavonoids found in food, has become perhaps the most studied flavonoid today.1 Quercetin scavenges free radicals. It can be consumed through foods naturally containing quercetin or through supplementation.

Quercetin gluosides, such as isoquercitrin, have been shown to be much more bioavailable.Quercetin primarily enters the diet as glycoside conjugates.2 One of the most abundant glycosidic forms present in plants is quercetin-3-glucoside (isoquercitrin), which is hydrolyzed in the small intestine and rapidly absorbed.2 Foods rich in isoquercitrin include leafy vegetables, broccoli, red onions, peppers, apples, grapes, black tea, green tea, red wine, and some fruit juices. The amount of quercetin received from food is primarily dependent on an individual’s dietary habits. Research has found a typical Western Diet provides approximately 0 to 30 mg of quercetin per day, but a diet rich in fruits and vegetables was estimated to provide more.1 It is also important to note, that the food content of quercetin reflects variations in soil quality, time of harvest, and storage conditions.

Quercetin 3-O-glucodise (Isoquercitrin) Content in Food

*Created from Phenol-Explorer, database on polyphenol content in foods 3

Food Amount
Grapes, black (100 g) 2.17 mg
Red Raspberry, raw (100 g) 3.58 mg
Nectarine, whole (100 g) 0.11 mg
Broccoli, raw (100 g) 1.80 mg
Red onion, raw (100 g) 1.80 mg
Black tea, infused (100 ml) 1.13 mg
Red wine (100 ml) 1.14 mg

Supplementing Quercetin

It is common practice to evaluate dietary supplements in terms of food equivalence. In some cases it is not reasonable to consume food to reach a therapeutic or evidence-informed level found in dietary supplements while other times, it is a worthwhile exercise. If a supplement provides 40 mg of quercetin as isoquercitrin per day, an individual would need to consume the equivalent amount of quercetin from food, by eating approximately 8½ cups of fruits or vegetables that have a quercetin content of 2 mg per 100 grams per day. Although this is within the recommended daily intake for servings of fruits and vegetables, the average consumption in the United States is much lower. Identifying foods rich in quercetin and analyzing the diet are a couple of simple ways to estimate daily consumption of quercetin and determine any supplementation considerations.

Be mindful of the power of flavonoids, and give special attention to quercetin and its applications. While a number of dietary assessment programs exist that evaluate everything from Calories, macronutrients, and micronutrients, these can be overwhelming for patients in many cases. Using an online database in relation to a specific food constituent can be an excellent exercise. Phenol-Explorer is one such online database. After evaluating a three-day food diary and noting, in this case, quercetin consumption can provide insight into whether or not lifestyle or dietary changes are required.

Learn more about quercetin and dosage guidelines.

Lauren Martin, MS, CNS

Lauren Martin is a Certified Nutrition Specialist practitioner who earned a Master of Science in Human Nutrition from Columbia University. She co-founded Martin Family Style, a lifestyle, food, and nutrition blog. Lauren is the lead author of the blog's nutrition section. She earned her Bachelor of Science in Nutrition from Oklahoma State University.

  1. D'Andrea G. Quercetin: A flavonol with multifaceted therapeutic applications? Fitoterapia. 2015;106:256-71.
  2. de Oliveira MR, Nabavi SM, Braidy N, Setzer WN, Ahmed T, Nabavi SF. Quercetin and the mitochondria: A mechanistic view. Biotechnology Advances. 2016;34(5):532-49.
  3. Phenol-Explorer, Database on polyphenol content in food, Food composition; http://phenol-explorer.eu/contents/polyphenol/293(Accessed October 18, 2016).
 

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* For dietary supplements: this statement has not been evaluated by the Food & Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.


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