Flavonoids are a type of compound found in many different foods. There are several thousand types, which are broken down into six subgroups: chalcones, flavones, flavonols, flavanones, anthocyanins, and isoflavonoids. They all serve a variety of functions in plants, and are thought to be associated with a number of health benefits for humans. They may be connected with some adverse health conditions as well, but there are no widely-reported side effects. There are many different sources of flavonoids, including berries, tea, wine, beer, chocolate, many vegetables, and most fruits.
Potential Health Benefits
Research on the potential health benefits of these compounds is mostly focused on the way they interact with other substances, especially in terms of their antioxidant activity. Antioxidant substances are able to change or neutralize the effects of reactive substances called free radicals that can damage cells, leading to disease. Many of the studies on flavonoids have been done on materials in test tubes or animals, so it's not entirely clear how effective they are in humans, but they may lower the risk of a variety of health problems, including cardiovascular disease, age-related degenerative diseases, and cancers. They may also help prevent tooth decay and reduce the occurrence of common illnesses, like the flu.
Flavonoids appear to have a symbiotic relationship with vitamin C, and are thought to change the way that cells associated with inflammation act, preventing or reducing it. Several studies show that they can disrupt the function of certain viruses and bacteria, including those associated with Human Immunodeficiency Virus (HIV) and certain types of herpes. They may also improve symptoms related to psychological disorders, including mood instability, memory problems, and depression.
Potential Side Effects
There are no widely known side effects of flavonoids, even when they are taken in very large concentrations; however, some people do appear to have individual sensitivities to specific kinds. One type, catechin, can cause a fever, anemia, and hives, though this is uncommon. Several studies showed that these substances do cause changes in certain genes like those associated with some cancers, but these results have not been seen in other studies.
Sources and Consumption
Most fruits and berries contain these compounds, though blueberries, cranberries, bananas, oranges, and apples are known for being particularly flavonoid-rich. Vegetables, especially broccoli, onions, spinach, eggplant, and tomatoes, are excellent sources as well. Beer, red wine, various nuts and beans, and dark chocolate also contain flavonoids, as do a wide range of teas. It's best to consume this nutrient directly from foods as part of a varied diet, rather than via a dietary supplement, as the effectiveness of isolated flavonoids is unclear. Cooking, processing, and high acidity environments all reduce the amount of flavonoids in foods.
Role in Plants
In plants, these substances provide pigmentation and help filter UV rays. They also help protect the plants from microbe, fungus, and insect attacks; and help plants survive frost and droughts. Additionally, they help promote or inhibit the growth of certain plant parts, including seeds and pollen tubes, and are used as chemical signals to tell plant cells when to stop or start doing things.