Plants naturally produce thousands of substances called phytochemicals. The flavonols are just one of many groups of phytochemicals, but they have the advantage of being better researched than many other phytochemicals, according to the May 2013 issue of “Antioxidants and Redox Signaling.” Like most of the phytochemicals, flavonols are active antioxidants that may protect your health through their ability to fight inflammation and neutralize free radicals.
List of Flavonols
Scientists have identified and categorized more than 8,000 phytochemicals. One of the biggest groups of phytochemicals, called flavonoids, is large enough that it’s further categorized into several other groups. Flavonols are one of the groups in the flavonoid family. You may hear about four major phytochemicals that belong in the flavonols: quercetin, kaempferol, myricetin and isorhamnetin. Flavonols are the most abundant flavonoids found in foods, according to a study published in the May 2004 issue of the “American Journal of Clinical Nutrition.”
Flavonols show strong antioxidant abilities in laboratory studies. A review of research published in the May 2013 issue of “Antioxidants and Redox Signaling” reports that quercetin provided anti-inflammatory benefits to cells from human blood vessels. The levels of free radicals in damaged lung cells decreased when they were treated with quercetin, according to a study published in the December 2013 online edition of the “Journal of Applied Toxicology.” Researchers using laboratory mice reported that the antioxidant effect of quercetin helped prevent nerve damage caused by a medication used to treat colorectal cancer, according to the October 2013 issue of “Molecular Pain.”
Bioavailability of Flavonols
The limited bioavailability of flavonols, which is the amount of the phytochemical absorbed and used by your body, impacts their effectiveness. Only a small amount of most flavonoids is absorbed and then quickly eliminated from your body, according to the Linus Pauling Institute. Your ability to absorb flavonols also depends on the type of bacteria thriving in your large intestine, since they help metabolize flavonoids. Quercetin is more easily absorbed than other flavonoids, noted the review in “Antioxidants and Redox Signaling.” You may also improve their bioavailability by eating flavonols together with healthy fats, according to May 2013 issue of “Molecular Nutrition and Food Research.”
Flavonol content in foods is often reported as a range because the amount they contain is influenced by exposure to sunlight. For example, the flavonol content is higher in the skin of fruit and in the outer leaves of greens because they absorb more sunlight. Yellow onions are the best sources of flavonols. They’re followed by leeks, cherry tomatoes, broccoli and blueberries. Other good choices for adding flavonols to your diet include apricots, apples, black grapes, green beans and tomatoes. If you enjoy a cup of red wine, or green or black tea, you’ll also get flavonols.
- Antioxidants and Redox Signaling: Dietary (Poly)phenolics in Human Health: Structures, Bioavailability, and Evidence of Protective Effects Against Chronic Diseases
- University of California Davis: Some Facts About Phytochemicals
- American Journal of Clinical Nutrition: Polyphenols: Food Sources and Bioavailability
- Journal of Applied Toxicology: Quercetin Reduces Oxidative Damage Induced by Paraquat Via Modulating Expression of Antioxidant Genes in A549 Cells
- Molecular Pain: The Antioxidant Effects of the Flavonoids Rutin and Quercetin Inhibit Oxaliplatin-Induced Chronic Painful Peripheral Neuropathy
- Linus Pauling Institute: Flavonoids
- Molecular Nutrition and Food Research: Dietary Fat Increases Quercetin Bioavailability in Overweight Adults
- American Journal of Clinical Nutrition: Polyphenols: Food Sources and Bioavailability: Table 1: Polyphenols in Foods