Flavonoids, also known as bioflavonoids, are a class of phytochemicals synthesized only by plants. Bioflavonoids are important pigments responsible for producing pigmentation in flower petals. So, these phytochemicals facilitate pollination, besides providing protection against some harmful insects and microorganisms. There are basically six major classes of these phytochemicals- flavonols, flavones, flavanones, isoflavones, flavanols, and anthocyanins. The most commonly found flavonoids in food are, quercetin, epicatechin, oligomeric proanthocyanidins, myricetin, catechins, and xanthohumol. Flavonoids in Food As mentioned already, flavonoids are found only in plants. They are abundant in a large number of fruits and vegetables. Some of the most important dietary sources of these phytochemicals are, citrus fruits, strawberries, beans, blueberries, onions, pulses, ginkgo biloba, and spinach. Green, black, as well as white tea are also very rich in flavonoids. Dark chocolates and red wine are two other important sources of these phytochemicals. Honey can also be an important source of these phytochemicals depending on the type of flower, from which nectar has been collected. Health Benefits These phytochemicals act as antioxidants and neutralize the free radicals. So, they help minimize the damaging effects of free radicals on the body cells and tissues. A free radical is a chemically unstable molecule, as it loses one electron from its outer shell. In other words, a free radical has a single unpaired electron in its outer shell. The loss of one electron from the outer shell makes free radicals highly reactive. In order to stabilize, these molecules need an electron, and this is the reason why they oxidize the healthy body cells and tissues. Free radicals are mainly produced as byproducts in the vital biochemical processes taking place within the body. Some free radicals enter the body from external environment, usually from cigarette smoke, alcohol consumption, electromagnetic radiation, overexposure to sunlight, consumption of processed foods, air pollution, etc. Even stress can generate a high level of free radicals in our body. Flavonoids as antioxidants help neutralize and stabilize the free radicals, so that they cannot damage the healthy cells and tissues. They provide protection against a number of diseases, including cancer, heart diseases, diabetes, tumor, etc. These phytochemicals can also help prevent atherosclerosis, which is a disease characterized by the deposition of fats inside the arterial wall. Such deposition narrows the arteries, and thereby hinders the flow of blood to the vital organs, like the heart and the brain. So, this disease can increase the risk of heart attacks and strokes. Flavonoids can lower the risk of coronary heart disease by preventing atherosclerosis. They are also known to have anti-inflammatory, anti-allergic, and antiviral properties. They can lower the risk of arthritis, osteoporosis, allergies, and viral diseases caused by the herpes simplex virus, parainfluenza virus, and adenovirus. They can suppress platelet aggregation, which is associated with diseases, like atherosclerosis and acute thrombus platelet formation. It has been found that due to their antiulcer effect, bioflavonoids can inhibit the formation of peptic ulcers. Some studies have also revealed that phytochemicals, like quercetin and epicatechin can have antidiarrheal effect. So, bioflavonoids are basically polyphenols that have antioxidant, anti-inflammatory, antiviral, anticancer, antitumor, and anti-diarrheal properties. They can enhance the natural immune response of the body against infectious agents, allergens, and carcinogens more efficiently.