The ultimate guide to Quercetin

Quercetin: immune system and antioxidant effects

In recent times, Quercetin has grown in popularity from a lesser known supplement to one of high demand, and rightly so... Quercetin is one of the most powerful and abundant flavonoids consumed in the human diet. So what exactly is Quercetin?

Quercetin is actually a pigment that belongs to a group of compounds found in plants called flavonoids. It is found in a wide variety of fruits and vegetables and accounts for 75% of our daily flavonoid intake. Foods rich in quercetin include onions, apples, berries, citrus fruits, grapes, kale, buckwheat, broccoli, tomatoes, black tea and red wine. The concentration of Quercetin can differ depending on the type of plant; which part of the plant is used; as well as its country of origin. 

Quercetin plays an important role in supporting a healthy immune response and fighting free radicals.

Quercetin is one of the most abundant antioxidants available in the human diet with an estimated average daily dietary intake between 10-100 mg daily. Antioxidants are compounds that are able to bind to free radicals in the body and effectively neutralise them. Free radicals are unstable molecules that can be found in our body and, if left to multiply, they can cause cellular damage. Quercetin has been found to be more powerful as an antioxidant than vitamins C and E.

Immune Function:

Quercetin has been found to exhibit immunomodulatory properties and may positively influence immune function. It appears to stimulate T-helper cells that produce Th-1-derived Interferon-y (IFN-y) while down-regulating Th2-derived Interleukin-4. T-helper cells are said to be the most important cells in adaptive immunity, as they help to activate B cells, secrete antibodies, and assist macrophages (a type of white blood cell) - all of which may help support the immune system to fight illness. Adaptive immunity is often referred to as the acquired immune system.

Interestingly, research also suggests that co-administration of vitamin C with Quercetin exerts a synergistic action due to the capacity of ascorbic acid (vitamin c) to recycle Quercetin into its active form, thereby increasing its bioavailability.


As an antioxidant, Quercetin acts as a scavenger of reactive oxygen and nitrogen species - highly reactive ions that are either generated through metabolic processes or following exposure to toxins, radiation or other exogenous sources. Accumulation of these molecules within the body can result in increased oxidative damage to DNA, proteins and lipids. Quercetin is able to form metal ion complexes to prevent further free radical generation. 


High potency QU995 is one of the purest Quercetin flavonoid polyphenols available in the market today - at 99.5% purity it offers a higher amount of Quercetin per dose compared to lower purity supplements commonly available in the marketplace. QU995 is sustainably sourced from Fava beans grown in Brazil with the scientific names Dimorphandra mollis and Dimorphandra gardneriana.

Picture of Fava Beans in a low dish placed on a beige tea towel