What is quercetin?
A natural pigment
Quercetin, or “quercetol”, is a natural pigment belonging to the flavonoid family. Bright yellow in color, it is present in many fruits and vegetables. It is notably found in the following plant sources:
- sarrasin
- oignons rouges
- câpres
- fruits (bleuet, pomme, raisin, cerise, canneberge…)
- herbes aromatiques (livèche, persil, ciboulette, aneth…)
It is also an active compound of certain medicinal plants such as ginkgo biloba and St. John’s wort.
A dietary supplement
Quercetin is primarily known for its antioxidant activity.
When taken as a dietary supplement, it protects the body from cellular aging and fights oxidative stress.
As shown by this study, it also slows the decline of cognitive functions related to aging or Alzheimer’s disease.
Additionally, it has anti-inflammatory effects. It reduces symptoms and relieves pain from rheumatoid arthritis.
Finally, it supports the immune defenses and regulates allergic reactions (asthma, rhinitis, atopic dermatitis…) thanks to its antihistamine action.
It is available in capsules, tablets, or liquid form.
Read also | How to choose the best quercetin?
Although taking quercetin has benefits, its consumption is not recommended for some people. It can also cause side effects.
When is it contraindicated?
If you have thyroid problems
People suffering from thyroid disorders (hyperthyroidism, hypothyroidism…) should avoid consuming it.
Indeed, as shown by this study, it can interfere with thyroid function.
If you have stomach problems
Its consumption can cause stomach pain, particularly if quercetin is taken for too long.
It is therefore not recommended for people with a sensitive stomach or who suffer from a gastric ulcer.
If you have kidney problems
In the long term, taking quercetin can cause kidney problems. Avoid consuming it if you already suffer from kidney problems (kidney stones, kidney failure…).
If you are taking certain medications
If you are taking medication, consult your doctor before consuming it.
Indeed, it can reduce the effects of certain medications such as antibiotics, antihypertensives, antidiabetics and anticoagulants.
In addition, it amplifies the anticoagulant effect of milk thistle, turmeric, ginger and flax seeds.
In pregnant and breastfeeding women
To date, no study has shown a potential danger of quercetin in pregnant or breastfeeding women.
However, in the absence of sufficient data on this subject, its consumption should be avoided.
What are its side effects?
Main side effects
If taken for too long or at a high dosage, it can cause adverse effects. The most common ones include:
- maux de tête
- douleurs gastriques
- problèmes rénaux
Stop taking it and consult a doctor if the side effects do not subside.
Precautions for use
To avoid potential side effects, quercetin should be taken short-term (maximum 3 months). Allow a break between each supplementation period.
Always follow the dosage indicated by the manufacturer. On average, it ranges between 500 and 1500 mg per day for an adult.
It should be taken on an empty stomach in the morning or between meals for better absorption by the body.
