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What is Quercetin? Benefits, Uses, Supplements and Side Effects

Quercetin is a flavonoid, that is, a natural pigment that can be found in fruits, vegetables, grains, tea, and wine. Likewise, there is scientific evidence that suggests that these compounds are capable of reducing the risk of developing heart and neurodegenerative diseases.

Another benefit attributed to flavonoids is that they act as antioxidants. Now, although it is considered safe, exceeding the dose of supplements can cause headaches, stomach problems and tingling. Find out what you need to know about it below.

Health Benefits of Quercetin

Quercetin also stands out as the most abundant flavonoid in the diet. Let’s see in detail how it can benefit health.

1. Decrease inflammation

A study published in The American Journal of Clinical Nutrition found that quercetin can reduce markers of inflammation, such as tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6).

Similarly, a study in women with rheumatoid arthritis found that taking 500 milligrams of this substance is capable of reducing the stiffness and morning pain associated with the disease. In addition, it was evidenced that the patients had reduced inflammation markers.

Now, as promising as these results are, more research on its anti-inflammatory properties is still required.

2. Relieve allergy

It is shown that quercetin inhibits enzymes that cause inflammation and eliminates substances that cause allergic symptoms, such as histamine. Likewise, a study in rodents showed that taking supplements of this flavonoid can prevent an anaphylactic reaction from occurring.

However, more research is needed to determine if this natural pigment can have the same effects in humans.

3. Fight cancer

There is scientific evidence linking the antioxidant properties of quercetin with its ability to fight cancer. Additionally, test tube and rodent research found that the flavonoid affects growth and kills prostate cancer cells.

Finally, another test-tube study in rats showed similar results in cancer cells of the liver, lung, breast, ovary and colon. However, human studies are still required and this compound cannot be considered a first-line approach in cancer conditions.

4. Reduce the risk of developing brain disorders

According to research published in Oxidative Medicine and Cellular Longevity, the antioxidant properties of this pigment can prevent the development of neurodegenerative diseases.

A study in rodents with Alzheimer’s showed that receiving quercetin injections every 2 days for 3 months reduced several markers of the disease. Likewise, the mice performed better in the learning tests to which they were subjected.

Similarly, another study in mice with Alzheimer’s showed that a diet rich in this flavonoid is capable of decreasing markers of the disease and improving brain function. However, it should be taken into account that these effects occurred in the middle-early stage of the disorder; in the mid-late stage there was no response or it was very mild.

Finally, there is scientific evidence that coffee, thanks to its quercetin content, can reduce the chances of suffering from this pathology. However, more studies are still required in this regard.

5. Lower blood pressure

According to a study published in The Journal of Pharmacology and Experimental Therapeutics, this flavonoid has the ability to relax blood vessels, which lowers blood pressure. Similarly, a study in mice with hypertension found that daily intake of quercetin for 5 weeks reduced systolic blood pressure by 18% and diastolic blood pressure by 23%.

Lastly, a review of human studies found that taking more than 500 milligrams a day lowers both systolic and diastolic blood pressure. However, more research is still needed to certify these effects.

Other Possible Benefits

The flavonoid is also associated with other benefits:

  • Fight aging: there is scientific evidence that this natural pigment can suppress aging cells, as well as decrease the markers of aging.
  • Improve athletic performance: According to a review of studies published in Medicine and Science in Sports and Exercise, ingesting quercetin is linked to greater endurance during sports.
  • Control blood sugar levels: it has been shown that this flavonoid is capable of lowering blood sugar levels and, therefore, preventing diabetes complications.

Where to find quercetin?

As we have mentioned, quercetin can be found in a large number of foods:

  • Onions (red and white).
  • Red apples.
  • Berries (blueberries, raspberries).
  • Tea (green and black).
  • Peppers (yellow and green).
  • Red grapes.
  • Broccoli and kale.

Of course, the concentration of the substance depends on how the food was grown. An example of this are organic tomatoes, which have 79% more quercetin than conventional ones. Although this difference was not observed in bell peppers.


Besides being present in a wide variety of foods, quercetin can also be consumed in supplement form . This can be in powder or capsules and the daily doses vary between 500 and 1000 milligrams.

However, it should be noted that the body does not absorb the pigment well, so that manufacturers tend to combine supplements with other chemicals, such as vitamin C.

Safety and side effects

Present in fruits, vegetables, and grains, quercetin is considered safe to consume. Even supplements have very little risk, as ingesting more than 1000 milligrams causes headaches, stomach problems, and tingling in rare cases.

Likewise, quercetin present in food is considered safe for pregnant and lactating women. However, supplements should be avoided in these population groups due to the lack of corroborating studies.

Quercetin: a natural pigment with a lot of potential

Quercetin is a flavonoid that stands out for the different ways in which it can contribute to health. From reducing inflammation, blood pressure and the risk of developing degenerative disorders to alleviating allergy symptoms.

Likewise, it has very few side effects. In fact, it is naturally safe to consume. The only risk that exists is in the supplements.

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