Quercetin: Effects, Uses & Risks

It is quercetin, a naturally occurring yellow pigment in many plants. The effect of quercetin is that of a radical scavenger. Exactly how this effect occurs has not yet been scientifically proven.

What is quercetin?

It is quercetin, a naturally occurring yellow pigment in many plants. The action of quercetin is that of a free radical scavenger. Quercetin belongs to the flavonols subgroup and to the flavonoids and polyphenols group. It is a pigment found in plants in the color yellow. Quercetin occurs in many foods and is mostly found in the peels. For this reason, large amounts of quercetin are lost when many fruits and vegetables are peeled. The processing of food in the kitchen can also partially destroy quercetin. Fruits and vegetables with a particularly high quercetin content include lovage, onions, tea, apples, blueberries, black currants, raspberries, blackberries, cherries, chives, rowan, sea buckthorn, organically grown tomatoes, kale, red grapes or capers. Since quercetin is found in grapes, it remains present in wine. Quercetin is also offered in concentrated form as a medicine to treat various diseases.

Pharmacological action

The exact mode of action of quercetin is still the subject of research and is being intensively investigated in scientific studies. In general, quercetin has been shown to inhibit oxidation processes in vivo. However, it has not yet been possible to conclusively clarify how this actually occurs. One of the things that has been generally proven so far is that quercetin is a natural antagonist of histamine. Quercetin also has a fundamental anti-inflammatory effect in the body. This property has also been shown to protect against neurodegenerative diseases. In addition, quercetin also promotes blood circulation and lowers blood pressure, although it has not yet been possible to explain why this is so. High levels of quercetin can increase the number of mitochondria in muscle cells. Likewise, quercetin prevents dioxins in the body from doing damage in various places. This also has to do with its antioxidant properties. Together with vitamins A, C, and E, as well as other bioflavonoids (catechins, for example), quercetin is even more effective because these natural substances complement each other in their effects.

Medical application and use

One of the most important properties of quercetin is that it has been shown to be helpful in the treatment of cancer, although it has not yet been conclusively determined what specifically happens in the body during this process. Quercetin has been shown to inhibit inflammation of all kinds. In this way, it has been shown to be helpful in the treatment of many allergic diseases. It protects against hay fever, asthma and other respiratory conditions, allergic skin reactions and other such reactions. It has also been shown to protect against inflammatory diseases of the prostate. In addition, quercetin has been shown to have a preventive effect on neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. In this case, too, it is assumed that this is related to quercetin’s property of having an anti-inflammatory effect. However, the exact mode of action is still under investigation in the case of these diseases as well. Regarding the helpful effect of quercetin in the treatment of cataracts, it is believed that in this case quercetin inhibits the conversion of glucose to sorbitol by having an inhibitory effect on the enzyme aldose reductase. Similarly, quercetin has a general inhibitory effect on various viruses in the body. The fact that quercetin has been shown to promote circulation and lower blood pressure is attributed in part to its inhibition of platelet aggregation. Quercetin may also protect the testes from the damage caused by dioxins and, due to its ability to promote the formation of more mitochondria in muscle cells, help increase athletic performance.

Risks and side effects

Dosage determines whether quercetin can cause side effects and damage to health. In its natural form in food, quercetin is very healthy and also cannot cause any harm. However, as a chemically manufactured product, it is toxic in very high concentrations.Therefore, it is important to follow the dosage instructions exactly when quercetin is administered as a medication for the treatment of diseases or for prevention. From only mild to severe headaches or a tingling sensation in the arms and legs to damage to the kidneys, overdoses can also cause side effects. High doses of quercetin can also cause mutations in germ cells. Since quercetin not only prevents tumor cells from growing, but can even kill them, especially in the case of cancer, the doctors treating the patient must carefully weigh up whether quercetin should nevertheless be used as a drug with possible side effects. With respect to other drugs, quercetin slows the metabolism of cyclosporine and also inhibits the mode of action of some antibiotics.