Quercetin is a plant flavonoid found in many different kinds of fruits, vegetables, grains and leaves. It has been used as an ingredient in nutritional supplements and prepared foods. Some commercial manufacturers draw water and moisture out of quercetin, forming a compound called quercetin dihydrate, which is said to be a more effective and highly concentrated form of the compound. Quercetin has been marketed as a nutritional supplement that has the ability to reduce inflammation, allergies and body fat. Several potentially serious side effects may result from quercetin dihydrate use; therefore, check with your physician before use.
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People with sensitive stomachs may have difficulty digesting quercetin dihydrate, especially if taken in high doses and on an empty stomach. The most common side effects of quercetin dihydrate on your digestive system include an upset stomach, indigestion, acid reflux, heartburn, persistent abdominal cramps, nausea, vomiting, diarrhea, sweating and flushing of the skin. Taking quercetin dihydrate with food and fluids may decrease the risk of developing gastrointestinal side effects.
An allergic reaction to quercetin dihydrate can occur in some individuals as a result of your immune system over-responding and mistaking quercetin for a potentially harmful or toxic substance. When this occurs, your body produces histamine, an organic nitrogen compound that triggers an inflammatory response to fight off potential toxins. Signs and symptoms of an allergic reaction to quercetin include rashes, itching, difficulty breathing, wheezing, hives, mouth sores and swelling of the tongue, lips or throat.
When taken in small doses, quercetin dihydrate may reduce swelling and inflammation around your joints, which benefits individuals suffering from chronic inflammatory conditions such as arthritis. However, when high doses of quercetin dihydrate are consumed, it may have the opposite effects, acting as a pro-oxidant as opposed to an antioxidant. In high doses, quercetin dihydrate may cause an increase in inflammation and a worsening of the symptoms associated with various types of arthritis and other chronic inflammatory conditions.
Quercetin may interfere with the absorption and effect of several types of drugs, including antibiotics, because as an antioxidant, quercetin dihydrate competes for the same cellular receptors as many types of antibiotic medications. Quercetin dihydrate may also inhibit the production of certain enzymes in your body that are required for the breakdown and metabolism of drugs that are used to treat various types of cancer. In a 2010 study published by the journal "Nutrition and Cancer," researchers discovered that quercetin supplementation inhibits the effect of the breast cancer treatment drug, Taxol. Consult your physician if you are using any medications before supplementing with quercetin.