Numerous laboratory studies show that phytochemicals, compounds found in fruits and vegetables, protect against the harmful effects of free radicals. Of these compounds, vitamin C and flavonoids are among the most powerful antioxidants. Some evidence suggests that one of the most important flavonoids, quercetin, when combined with vitamin C, provides stronger protection against oxidative stress.
Quercetin is found in a variety of fruits and vegetables such as apples, cherries, onions, broccoli, berries, citrus fruits, tea and grapes. It is estimated that the average person receives 10-100 mg of quercetin daily through various sources  – one kilogram of raw broccoli contains 32 mg and kilograms of cherries 12 mg.
This flavonoid neutralizes some of the highly reactive free radicals such as peroxynitrite and hydroxyl radical. That is why it is available as a dietary supplement in powder and capsule form. However, quercetin alone has low bioavailability, which means that the body absorbs it in small amounts .
Unlike most dietary supplements, most of the quercetin in food is linked to a sugar molecule and this complex is known as glycoside. The absorption of quercetin depends in part on the chemical structure of glycosides, however several other factors such as the presence of vitamin C may enhance its bioavailability . This is one reason why quercetin supplements may include other compounds, such as vitamin C and digestive enzymes, e.g. bromelain, as they can increase its absorption. On the other hand, one of the characteristics of flavonoids is their ability to prolong the action of vitamin C.
A key function of vitamin C is to reduce certain dangerous oxidative reactions throughout the human body. But because vitamin C is water soluble, it does not stay in the body for long. This limits its action and so it is recommended to take it frequently during the day. Flavonoids improve the concentration and effectiveness of vitamin C. Quercetin and dihydroquercetin have been found to reduce the deactivation or oxidation of vitamin C, which allows it to have a longer shelf life . Like other flavonoids, quercetin can interact with aqueous and lipophilic endogenous antioxidants, further increasing the antioxidant stabilization of vitamin C. The protection provided by flavonoids is related to their ability to interact and interact. parts of which vitamin C.
In addition to antioxidant activity, some studies – but not all – have shown that quercetin may increase exercise performance and mitochondrial biogenesis. The combination of vitamin C and quercetin may reduce muscle damage and body fat ratio in male athletes.
Find in Vita4you.gr a great variety of supplements with quercetin.
- Health effects of quercetin: from antioxidant to nutraceutical.
- Quercetin: A flavonol with multifaceted therapeutic applications?
- Pharmacokinetics and bioavailability of quercetin glycosides in humans.
- Bioavailability of Quercetin.
- ESR studies of vitamin C regeneration, order of reactivity of natural source phytochemical preparations.
- Flavonoids as antioxidant agents: importance of their interaction with biomembranes.
- Quercetin’s influence on exercise performance and muscle mitochondrial biogenesis.
- Quercetin and Vitamin C Supplementation: Effects on Lipid Profile and Muscle Damage in Male Athletes.