Can an inconspicuous and lesser-known antioxidant like quercetin secretly improve your athletic performance without requiring you to train harder? Learn in this article how quercetin can help you and where to find this "superfood."
Table of contents
1. What is quercetin?
Quercetin is a bioflavonoid and polyphenol . It occurs as a yellow pigment in many natural foods , which we will explain in more detail later. Some studies have shown that it can have far-reaching, positive effects on human health and athletic performance .
2. What is the effect of quercetin?
There are many substances that have been studied more extensively than quercetin. However, in recent years, scientists have begun to analyze quercetin's effects more intensively.
In 2010, a group of American researchers from the Department of Exercise Science at the University of South Carolina discovered that the bioflavonoid can have a significant effect on fatigue while cycling .
For this study, 12 participants were divided into two groups. One group received 500 mg of quercetin twice daily for 7 days, while the second group received a placebo. VO2 max and time to fatigue were then measured while cycling.
The group that took a total of 1000 mg of quercetin daily improved VO2max values by 3.9% and slowed fatigue by 13.2%, while the placebo group measured an increase of less than 0.05% in each case.[1] Regarding delayed fatigue, Iranian researchers from the Isfahan University of Medical Sciences were able to confirm the results.[2]
In another study, the same scientists from the University of South Carolina found that in 18 adults between 60 and 89 years of age , subjects with quercetin supplementation walked measurably more steps per day and were able to increase their physical activity at a low and moderate level.[3]
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3. Side effects of quercetin
Short-term oral administration of quercetin is considered safe. In the studies mentioned, subjects were given the maximum daily dose of 1000 mg for no longer than 14 days. Quercetin is said to be safe in its natural form. Side effects from quercetin can occur if it is ingested or injected as a synthetic product in very high concentrations.
As with any other ingredient or food, the dose makes the poison. High doses of quercetin can be toxic and cause mild to severe headaches. Therefore, you should never exceed the daily dosage recommendations. [4]
4. Which foods contain quercetin?
Quercetin occurs naturally in many fruits and vegetables , which can easily be part of your daily diet. Depending on the preparation method, however, quercetin in foods can be destroyed by excessively high temperatures .
Peeling fruits and certain vegetables can also result in a large amount of flavonoid content being lost, as this is where most of the plant pigments are found.
Onions, in particular, contain a relatively large amount of quercetin with potent effects: A group of scientists from the Islamic Azad University investigated the antioxidant effects of quercetin from onion juice on the sperm health of rats.[5]
You can also find this antioxidant in broccoli, chives, kale, tomatoes, and green beans. Many berries, such as blueberries, raspberries, blackcurrants, blackberries, and cranberries, also contain this polyphenol.
If berries aren't your cup of tea, you can also find quercetin in the following fruits: red grapes , apples , cherries , and citrus fruits .
Overview of quercetin content in vegetables and fruit [6] per kg
- Capers 1730-2330 mg
- Liebstückel 1700 ng
- Radicchio 320 ng
- Fresh dill 550 mg
- Onion 284-486 mg
- Chives 245 mg
- Kale 60-110 mg
- Broccoli 22-32 mg
- Green beans 30 mg
- Tomatoes 2-27 mg
- Cranberries 156 mg
- Black currants 69 mg
- Blueberries 74-158 mg
- Raspberry 24 mg
- Blackberry 45 mg
- Kale 60 mg
- Blackberries 45 mg
- Apples 21-72 mg
- Grapes 10-31 mg
- Cherries 47 mg
5. Conclusion
Current studies show that quercetin can have a positive effect on your physical performance by increasing your VO2 max. VO2 max is your maximum oxygen uptake and indicates the maximum amount of oxygen your body can use per minute under stress (e.g., during exercise).
Furthermore, quercetin can improve your fatigue time during exercise. This means you can particularly benefit from the antioxidant's positive effects during endurance sports. You should make sure you use natural, high-quality quercetin and adhere to the recommended dosage.
6. Sources
[1] Davis, J. et al. (2010) International Journal of Sport Nutrition and Exercise Metabolism, p-56-62. The dietary flavonoid quercetin increases VO(2max) and endurance capacity. doi: 10.1123/ijsnem.20.1.56 [https://www.ncbi.nlm.nih.gov/pubmed/20190352]
[2] Daneshvar P. et al. (2013) International Journal of Preventive Medicine, p. 53-57. Effect of Eight Weeks of Quercetin Supplementation on Exercise Performance, Muscle Damage and Body Muscle in Male Badminton Players [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3665027/]
[3] Chen, S. (2011). University of South Carolina, Effects of Quercetin Supplementation on Physical and Mental Functions in Older Adults. (Doctoral dissertation). [https://scholarcommons.sc.edu/etd/1202/]
[4] Nonnenmacher, Dr. med. (2019) Quercetin. [https://medlexi.de/Quercetin#Risiken_.26_Nebeneffekten]
[5] Khaki, A. et. al. (2009) Folia Morphol, p. 45-51. Evaluation of androgenic activity of allium cepa on spermatogenesis in the rat. [https://www.ncbi.nlm.nih.gov/pubmed/19384830]
[6] Bhagwat S. et al. (2001) US Department of Agriculture, Release 3, p. 13-106. USDA Database for the Flavonoid Content of Selected Foods. [https://www.ars.usda.gov/ARSUserFiles/80400525/Data/Flav/Flav_R03.pdf]
