Quercetin: benefits, side effects, dosage and interactions


Quercetin is a chemical naturally found in various foods, including apples, onions, tea, berries, and red wine. This flavonoid is also found in some herbs like ginkgo biloba and St. John's wort.

Quercetin acts as an antioxidant by neutralizing free radicals, chemical by-products that damage cell membranes and damage DNA. Available as a dietary supplement, quercetin also has antihistamine and anti-inflammatory properties.

What is quercetin used for?

In alternative medicine, quercetin helps with the following conditions :

So far, the results supporting quercetin's benefits are mixed – some conditions are only tested in test tubes or on animals. This is what the study looks like:

Allergy relief

Quercetin is believed to prevent the release of histamine, an inflammatory chemical involved in allergic symptoms such as sneezing and itching, from certain immune cells. While laboratory experiments show that quercetin can help fight allergic conditions like allergic rhinitis , most have been done in vitro or on animals. The researchers recommend more human studies to test the correlation.

High blood pressure

A 2016 review of randomized controlled trials found that quercetin significantly lowered systolic and diastolic blood pressure , especially in diabetics who received at least 500 milligrams per day. The exact dosage and duration are not yet clear to see the maximum benefit.

Athletic endurance

Quercetin may be no better than placebo when it comes to improving athletic performance, according to a 2011 review of 11 previous studies. All studies have shown an increase in exercise endurance due to VO2 max (oxygen consumption during physical activity) when people took quercetin. but the effect was minimal.

Another study found a more impressive link. A 2013 study that looked at 60 male students who had participated in athletics for at least three years found that after taking quercetin, lean body mass, total body water, basal metabolic rate, and total energy expenditure improved after taking quercetin .


Cell culture studies have shown that quercetin can help slow the growth of certain types of cancer cells. Several in vitro and animal studies show that quercetin may protect against certain types of cancer, such as leukemia and lung cancer. For example, a 2010 study examined the relationship between quercetin intake and risk of lung cancer in 38 non-neoplastic lung tissues and found an inverse correlation: the higher the quercetin intake, the lower the risk .

However, since there is currently not enough human research to fight quercetin cancer, it is too early to say whether quercetin may play a significant role in cancer prevention.

Possible side effects.

Quercetin is generally well tolerated when used in adequate amounts. Some have reported tingling sensations in the hands and feet, as well as indigestion and headaches with oral quercetin. Very high doses, more than 1 gram per day, can cause kidney damage.

The safety of additives has not been tested and due to the fact that food additives are largely unregulated, the content of some products may differ from what is stated on the product label. Also note that the safety of supplements for pregnant women, nursing mothers, children, and people with medical conditions or taking medications, especially antibiotics, has not been established .

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Dosage and preparation

Under medical supervision, quercetin has been used safely in doses up to 1000 mg twice daily for 12 weeks. There is not enough evidence to know if it is safe for long-term use.

The right dose for you may depend on factors such as your age, gender, and medical history. Talk to your doctor for personalized advice if you decide to take this supplement.

What to look for

Dietary sources of quercetin include tea, onions, apples, buckwheat, and pow d'arco . When taking quercetin as a supplement, it may be helpful to choose a product that also contains papain and / or bromelain . These are enzymes derived from plants (fruit extracts) that have been shown to increase the intestinal absorption of quercetin .

Due to the lack of supporting research, it is too early to recommend quercetin for any medical purpose. If you plan to use it, check with your healthcare professional first. Treating a disease on your own and avoiding or delaying standard treatment can have serious consequences.

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