Quercetin is an increasingly well-known representative of the group of polyphenols and flavonoids, which, as natural dyes, are characterized in particular by their light yellow color (from Latin flavus; yellow). Flavonoids are biologically active plant compounds that, for example, have antioxidant and anti-inflammatory effects in humans. However, the body cannot produce quercetin itself and therefore absorbs it through food. A normal Western diet contains approximately 15 mg to 40 mg of quercetin daily.
Occurrence of quercetin in foods
The name quercetin comes from the Latin word Quercētum, which means oak forest and underlines its plant origin. Larger amounts of the molecule contain, for example, capers (234 mg per 100 g) and onions (11-33 mg per 100 g), Apples and berries (both 2-5 mg per 100 g), as well as various teas (black tea 2 mg per 100 g). Quercetin accumulates mainly in the outer parts of the plant . For the apple, it's in the peel.
Onions (especially their peel) are particularly rich in the vital substance quercetin.
How much quercetin is contained in food?
The content of quercetin in food varies greatly. We have listed the foods with the highest quercetin concentrations in the table. However, it must be said that these are average values. Depending on the growing season, these values can vary greatly. You can find a detailed list of several hundred foods here.
| Food | Quercetin content in mg per 100g |
| Capers | 233.84 |
| Dill | 55,15 |
| Oregano | 42.0 |
| Onions | 24.3 |
| Apples | 19.36 |
| Spring onions | 12.6 |
| Blueberries | 7.67 |
| Black tea | 2.19 |
How much quercetin do we consume through food?
Before we get to the dosages from the studies, let's take a quick look at natural quercetin absorption. Approximately 70-80% of all flavonoids that we consume with food contains a form of quercetin. This molecule occurs in various configurations in nature, usually in combination with different sugar molecules. However, this “saccharified” form is less absorbed by our body because quercetin is a fat-soluble molecule.
In this Japanese study it was measured exactly how much quercetin people consumed in the summer or consumed in winter. The result: About 15.5-16.2mg quercetin per day.
What dosage of quercetin is recommended?
Let's compare that with the studies: Most of the studies (so far) have taken place on animals, e.g.b Quercetin has been intensively researched in mice because it is expected to have effects against dementia. The dosages vary between 5mg per kg of body weight and 100mg per kg of body weight. In studies, an amount of 1000 mg of quercetin per day was found to be safe in humans.
In this study the mice received 100 mg of quercetin per kg of body weight for 8 days and the scientists found that this caused the mitochondria in the brain to function better again.
Conclusion about quercetin
Quercetin rightly bears its name as “King of the flavonoids”. This molecule has already demonstrated its positive effects in many animal and cell studies, and the initial results in humans are also hopeful. It remains to be seen to what extent quercetin can be used, but its various properties make quercetin an exciting candidate for longevity research. And the secondary plant substance also has all sorts of useful effects for everyday life.
