Quercetin is one of the most common flavonoids found in the human diet, particularly within fruits and vegetables. Flavonoids are known for their antioxidant and anti-inflammatory properties. As such, quercetin's primary use as a supplement is for the relief of allergies, inflammation and to reduce the effects of aging. Quercetin has been well researched in the lab, or in vitro, and within animals, but not as well on people. More research on quercetin's effects on inflammation within people needs to be done before health recommendations can be made. Ask your doctor before using any medicinal supplements.
Quercetin and Inflammation
Inflammation has been linked to many different conditions ranging from arthritis to heart disease. Inflammation is a reaction by the body to injury and foreign material in efforts to heal and prevent disease, but too often the symptoms caused by inflammatory reactions are worse than the underlying problem. Thus, controlling inflammation is useful. Quercetin, which is found in high levels in apples, onions and green tea, inhibits the pro-inflammatory arachidonic acid metabolites, which are needed for inflammation to occur. A study published in a 2008 edition of "Metabolism" found that animals fed high-fat diets and quercetin supplements experienced significant decreases in signs of inflammation. Another 2008 study, published in the journal "Nutrition," showed that supplementing with 1 microgram of quercetin for four weeks decreased inflammation markers by 23 percent and increased the antioxidant capacity in healthy volunteers.
Quercetin and Allergies
According to "Biochemical, Physiological and Molecular Aspects of Human Nutrition," quercetin is an effective inhibitor of histamine release, which is the primary cause of allergic reactions and symptoms. Specifically, it inhibits the manufacture and release of histamine and other allergic and inflammatory mediators from mast cells and basophils, which cause nasal discharge, watery eyes, hives and swelling. Both mast cells and basophils are immune-type cells that guard the mucous membranes of the respiratory system. Quercetin chalcone is the supplemental form often recommended for the management of allergies.
Quercetin and IBS
Irritable bowel syndrome, or IBS, is partly caused by allergic reactions to certain foods within the large intestine, which is referred to as gastric-mediated allergy. This process involves intestinal mast cells that release histamine when triggered by food allergens. Histamine increases the permeability of tiny blood vessels, which "leak" lymph fluid, white blood cells and proteins involved in inflammation. According to the "Professional Guide to Diseases," the majority of people with IBS experience this type of inflammation, which could be mediated by natural histamine inhibitors such as quercetin.
Quercetin and Heart Disease
Due to quercetin's ability to reduce inflammation, it may also have a significant impact on heart disease and other cardiovascular conditions, such as atherosclerosis. Some research has found that quercetin influences the process that causes damage to coronary artery walls and other vessels that feed the heart by reducing the inflammatory process and levels of free radicals within arteries, as cited in "Human Biochemistry and Disease." As such, quercetin may be able to reduce the risk of heart attack and stroke, although more research is needed in this area.
Quercetin and Gene Control
According to "Nutritional Sciences," quercetin can also reduce inflammation by interacting with DNA sequences at the genetic level. Specifically, it influences production of the inflammatory marker TNF, which can help prevent systemic inflammation and insulin resistance.
References
- "Metabolism"; Quercetin transiently increases energy expenditure but persistently decreases circulating markers of inflammation in C57BL/6J mice fed a high-fat diet; L.K. Stewart et al.; July 2008
- "Nutrition"; In vitro and ex vivo anti-inflammatory activity of quercetin in healthy volunteers; A.W. Boots et al.; July 2008
- "Biochemical, Physiological and Molecular Aspects of Human Nutrition"; Martha Stipanuk; 2006
- "Professional Guide to Diseases: Ninth Edition"; Springhouse Publishing; 2009
- "Human Biochemistry and Disease"; Gerald Litwack; 2008
- "Nutritional Sciences"; Michelle McGuire; 2007
