Quercetin For Colds

Quercetin is a plant compound found in various foods that has a wide range of beneficial effects on the body. It also seems to be very promising for the prevention and treatment of colds. Because quercetin can reduce the severity of symptoms and the number of sick days as well as the susceptibility to upper respiratory tract infections.

Quercetin, a plant compound against colds

Quercetin is a yellow natural dye, belongs to the flavonoid group, and is contained in many foods (see list at the bottom of the text). The plant substance has a variety of effects on health and, according to various studies, can also be used preventively and therapeutically for colds.

Quercetin: the effects

Researchers found that quercetin has beneficial effects on the body at various levels. On the one hand, it has an antioxidant effect and can thus interrupt the chain reaction of free radicals, which attack the cells and can lead to oxidative stress, thus preventing cell damage.

Other positive effects of quercetin include the following:

  • anti-inflammatory
  • anticancer
  • antiviral
  • antiallergic
  • protects the heart
  • can protect the brain from damage caused by radiation.

Quercetin in upper respiratory infections

The most common infections of the upper respiratory tract are the so-called colds, which usually cause symptoms such as a runny or stuffy nose, as well as pain when swallowing, fatigue, or a cough. The studies presented below were able to show a positive effect of quercetin preparations in infections of the upper respiratory tract.

Reduction in sick days and symptom severity

A placebo-controlled, double-blind, randomized study showed that taking quercetin twice a day (in the morning after waking up and between 2 p.m. and the last meal of the day) for 12 weeks led to a reduction in symptom severity and the number of sick days. People aged 18-85 with different levels of fitness were studied, but the positive effect of quercetin supplements was only seen in those who rated themselves as physically fit and were 40 years or older.

Fewer infections after intense training

Further studies have highlighted the effects of quercetin after intense exercise as it is associated with an increased risk of upper respiratory tract infections (5). A reduction in new cases was shown when quercetin was taken 3 weeks before and 2 weeks after physical exertion.

It was also observed in mice given an influenza virus that quercetin could offset the increased susceptibility to infection after intense physical exertion.

Antiviral effects of quercetin

In vitro studies (carried out outside of a living organism) have demonstrated potent antiviral properties of quercetin against both adenoviruses and coronaviruses, both of which can be the cause of upper respiratory tract infections.

You can find more ways to protect yourself from coronavirus in the article Over-the-counter remedies to prevent Covid-19, where we present a concept that includes: also belongs to quercetin.

Taking quercetin for colds

Quercetin can therefore have an extremely positive effect on infections of the upper respiratory tract. Due to the low risk of side effects with the right dosage (see below), quercetin preparations can be integrated into the prevention and treatment of colds without hesitation. Quercetin can also be a good supplement to help prevent upper respiratory tract infections that can occur after strenuous exercise.

The beneficial effects of the above studies were attributed to a dose of 500 mg twice daily quercetin taken for up to 12 weeks. An increase in the quercetin plasma level was recorded without any side effects. We, therefore, recommend not to exceed this length of time and dose, as it is not known whether long-term use is safe.

Combination of quercetin with other vital substances

Taking other plant compounds (e.g. resveratrol, catechins) and curcumin can increase the effects of quercetin so that the positive effects can occur at lower doses. Furthermore, the effects of quercetin can be enhanced by the additional intake of vitamin C or bromelain.

Quercetin is also a zinc ionophore and makes the cell membrane permeable to zinc ions so that the cell can be better supplied with them. Since zinc plays an important role in strengthening the immune system, these two substances can also be combined well.

Possible side effects

Ingesting quercetin through foods such as fruits and vegetables is very healthy and cannot cause any harm to the body. In the form of dietary supplements, quercetin is considered safe if a dose of 1000 mg/day is not exceeded for 12 weeks. However, it is not known if larger amounts and long-term use are safe because there are no concrete studies on this.

In high doses (more than 1000 mg/day), quercetin can cause headaches or tingles in the arms and legs. When administered intravenously, overdose can also cause kidney damage. If you experience side effects while taking quercetin supplements, contact your doctor.

Possible drug interactions

If you are on medication, consult your doctor before taking quercetin supplements, as quercetin may alter how the medication works and increase the risk of side effects.

In children and during pregnancy

Since there are no studies on quercetin and its effectiveness or possible side effects for pregnant women and children under the age of 12, no quercetin preparations should be taken as a precaution. In the form of food, quercetin can of course also be consumed by these groups of people without any worries.

Quercetin in food

Quercetin is found in a wide variety of fruits and vegetables as well as in cereals and pseudocereals. These include, for example, capers, apples, berries, onions, tomatoes, or buckwheat. The following are particularly good sources of quercetin, with the quercetin value always – unless otherwise stated – referring to 100 g of the raw food:

  • Capers (in a jar) 180 mg
  • Lovage 170 mg
  • Dill 55 mg
  • Red Leaf Cut Lettuce (Lactuca sativa L. var. crispa) 10 – 30 mg
  • Buckwheat 23 mg
  • Asparagus 23 mg
  • Cocoa powder 20 mg
  • Cranberries 15 mg
  • Romaine Lettuce (Lactuca sativa L. var. longifolia) 12 mg
  • Onions 11 – 41 mg
  • Aronia berry 9 mg
  • Kale (type of kale) 7 mg
  • Apples with skin 4.5 mg (Fuji 2.3 mg)
  • Cherry tomatoes 3.3 mg
  • Apple peel 2.1 mg
  • Tomatoes 1.6 mg
  • Broccoli 0.5 – 1.6 mg

While the quercetin content of apples may sound low compared to that of lovage or capers, it is easy to eat two apples which (if one weighs 100g) provide 9mg of quercetin, at least as much as 5g of lovage.

More quercetin in old apple varieties

However, be careful to use older variety apples, as newer varieties (e.g. Fuji) seem to contain significantly less quercetin. Older apple varieties are generally richer in botanicals – and they’re also less allergenic, as we explain in our article on the five benefits of apples.

The anti-allergenic effect of old apple varieties may also be due to their higher quercetin content. Because quercetin protects against allergies and allergic reactions. It stabilizes the cell membrane of the mast cells and thus prevents them from releasing histamine and other inflammatory messengers too quickly. Histamines are the substances that lead to allergic reactions in the body: swelling of the mucous membranes, reddening, and itching.

Quercetin is heat stable

Quercetin passes into the cooking water during cooking but is not destroyed. Therefore, if you cook vegetables, then use the cooking water e.g. B. for sauces or soups. It is easier to steam the vegetables or prepare them in a pan. According to one study, quercetin levels are not reduced during pan frying or microwave cooking.

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