Bioflavonoids, or flavonoids, are a large class of antioxidants. They are compounds abundant in the pulp and rinds of citrus fruits and other foods containing vitamin C, such as soybeans and root vegetables. Other major sources of bioflavonoids include tea, vegetables such as broccoli and eggplant, flaxseed, and whole grains. Bioflavonoids are active ingredients in many herbal remedies. These include feverfew, Tanacetum parthenium; Ginkgo biloba; licorice root, Glycyrrhiza glabra; St. John's wort, Hypericum perforatum; and Echinacea spp.
Bioflavonoids help maximize the benefits of vitamin C by inhibiting its breakdown in the body. In 1935, Albert Szent-Györgyi demonstrated that an extract he called citrin, made from lemon peels, was more effective than pure vitamin C in preventing scurvy. In 1936, Szent-Györgyi found that citrin was a mixture of bioflavonoids, including the flavone hesperidin and a flavonol glucoside. Szent-Györgyi believed that bioflavonoids should be considered vitamins, but was not able to substantiate that they were essential nutrients. Still, many researchers and physicians believe that dietary intake of bioflavonoids is beneficial for blood vessel health and possibly for protection against heart disease.
Bioflavonoids are categorized in a variety of ways, sometimes with overlapping categories. Types of bioflavonoids include flavones, isoflavonoids, flavanones (such as catechins and naringin), and flavanols.
In their natural state, bioflavonoids are usually found in close association with vitamin C. In treating conditions, vitamin C and bioflavonoids each enhance the action of the other compound. Therefore, when taken as supplements, they often should be used in combination to increase effectiveness. In general, all bioflavonoids are potentially useful as antioxidants, antivirals, and anti-inflammatories. Other health benefits of the various bioflavonoids include:
- preventing nosebleeds, miscarriages, postpartum bleeding, and other types of hemorrhages
- the treatment and prevention of menstrual disorders
- protection against cancer and heart disease
- anticoagulant activity (preventing blood clotting)
- reducing the occurrence of easy bruising
- decreasing the cholesterol level
- improving symptoms related to aging
- protection against infections
- counteracting the effects of pollution, pesticides, rancid fats, and alcohol
- ability to reduce pain
- improving the circulation
- improving liver function
- improvement of vision and eye diseases
- strengthening the walls of the blood vessels
Major bioflavonoids and their actions
Rutin can be used to treat chronic venous insufficiency (condition in which blood drains inadequately from a body part), glaucoma, hay fever, hemorrhoids, varicose veins, poor circulation, oral herpes, cirrhosis, stress, low serum calcium, and for cataracts. It is helpful in reducing weakness in the blood vessels and the resultant hemorrhages. Rutin can relieve the pain from bumps and bruises. Rutin may be taken to help reduce serum cholesterol. It is also useful in treating rheumatic diseases such as gout, arthritis, systemic lupus erythematosus (a chronic disease marked by a rash on the face with a variety of symptoms), and ankylosing spondylitis (condition affecting ligaments in the spine, involving the hips and shoulders). Rutin is most abundant in apricots, buckwheat, cherries, prunes, rose hips, the whitish rind of citrus fruits, and the core of green peppers.
Anthocyanins and proanthocyanidins can be used to treat a number of eye conditions such as cataracts, night blindness, diabetic retinopathy (progressive retina disease that is a complication of diabetes), and macular degeneration (a hereditary condition causing loss of vision). They are also useful for strengthening the walls of the blood vessels, and therefore may help prevent bruising, hemorrhoids, varicose veins, and spider veins. These bioflavonoids can help to prevent osteoporosis by stabilizing collagen, the major protein in bone. They can reduce cholesterol deposits in arteries, and prevent damage to the artery walls. These actions reduce the possibilities of heart disease and strokes. Anthocyanins and proanthocyanidins can dilate the blood vessels and prevent blood clots. Proanthocyanidins are able to cross the blood-brain barrier to protect the brain from damage by free radicals and infection. Good sources of anthocyanins and proanthocyanidins include blackberries, cranberries, black and green tea, raspberries, grapes, eggplant, red cabbage, elderberries, and red wine.
Hesperidin is useful in treating the complaints of menopause and in dealing with the viruses that cause herpes, the flu, and certain respiratory ailments. Hesperidin fights allergic reactions by blocking the release of histamine. It may also help reduce edema (accumulation of fluid) in the legs. Hesperidin deficiency has been linked to weaknesses in the walls of the blood vessels, pain and weakness in the hands and feet, and leg cramps at night. Hesperidin is mostly found in the pulps and rinds of citrus fruits.
Ellagic acid helps to inhibit cancer by neutralizing the effect of certain carcinogens. It is particularly helpful in reducing the effects of nitrosamines, which are found in tobacco and processed meat products such as bacon and hot dogs. Ellagic acid reduces the effects of the toxic and carcinogenic factors (aflatoxins) produced by Aspergillus flavus molds on food. Aflatoxins may cause liver damage and cancer. Ellagic acid diminishes the effects of polycyclic hydrocarbons produced by tobacco smoke and air pollution, as well. Sources of ellagic acid include strawberries, grapes, apples, cranberries, blackberries, and walnuts.
Quercetin is a good antihistamine. It can help reduce the inflammation that results from hay fever, allergies, bursitis, gout, arthritis, and asthma. It may lessen other asthma symptoms. Quercetin stimulates detoxification in the liver. It strengthens the blood vessels, and is useful in treating atherosclerosis (plaque build-up in the arteries) and high cholesterol levels. It may help inhibit tumor formation. Quercetin can be used to treat many of the complications of diabetes. For example, it blocks the accumulation of sorbitol, which has been linked with nerve, eye and kidney damage in diabetics; and it regulates blood sugar levels. Quercetin inhibits the growth of Helicobacter pylori, which has been implicated in the development of peptic ulcers. It can also help diminish the effects of the herpes virus, the Epstein-Barr virus (a common virus; a common cause of mononucleosis), and the polio virus. Quercetin is found in green tea, onionskins, kale, red cabbage, green beans, tomatoes, potatoes, lettuce, strawberries, cherries, and grapes. It is also found in smaller amounts in many other foods.
Catechins and tannins can be used to stimulate detoxification by the liver and to strengthen the blood vessels. They also help reduce the inflammatory response. Catechins and tannins may help inhibit the formation of tumors. In addition, catechins can be used to inhibit the breakdown of collagen and to treat hepatitis and arthritis. Catechins and tannins are both found in green and black teas.
Kaempferols stimulate liver detoxification and strengthen the blood vessels. They may also inhibit tumor formation. Strawberries, leeks, kale, broccoli, radishes, endives, and red beets all are good sources of kaempferols, but kaempferols are very common and found in many plants and foods. Naringen may slow the progression of heart disease and visual degeneration in diabetes. It is a potent anticoagulant that keeps the arteries clear and strong to prevent strokes, heart attacks, and the blindness of diabetes. Naringen is an active ingredient of in grapefruits. Genestein is known to be a regulator of estrogen. It is good for treating disorders of men-struation
Since bioflavonoids are so widely available in fruits in high concentrations, daily servings of whole fresh fruits and fresh fruit juices should be consumed. Highly concentrated liquid extracts of some fruits are also available.
Bioflavonoids are generally safe, even at very high doses. However, pregnant women are advised not to take megadoses of bioflavonoids. Preliminary studies have indicated that there may be a link between infant leukemia and high doses of bioflavonoids in the mother.
Bioflavonoids are not toxic, even at high levels. They are water soluble, and therefore, any in excess of what is needed by the body is excreted in the urine.
Bioflavonoids are usually found in close association with vitamin C, and they enhance its effect. There are no known drug interactions.
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