Alternative names: Riboflavin, Vitamin B-2.
Vitamin B2 is an antioxidant nutrient that helps the body inhibit the formation of damaging free radicals. It enhances adrenal/heart functions, prevents deterioration of blood vessels, and helps to prevent arterial sclerosis (hardening of the arteries).
Vitamin B2 is an orange-yellow crystal that is stable to heat, acid and oxidation. Intestinal bacteria produce varying amounts of Riboflavin, so it is unclear what different people's needs for B2 are. This may minimize the degree of Riboflavin deficiency, even with diets low in riboflavin intake. Though there are many deficiency symptoms possible with low levels of B2 in the body, no specific serious deficiency disease is noted for riboflavin, as there is for vitamins B1 and B3 (niacin). Riboflavin-5-phosphate, a form of riboflavin, may be more readily assimilated by some people.
Vitamin B2 is easily absorbed from the small intestine into the blood which transports it to the tissues. Excess intake is eliminated in the urine, which can give it a yellow-green fluorescent glow, commonly seen after taking B-complex 50mg or 100mg supplements. Riboflavin is not stored in the body, except for a small quantity in the liver and kidneys, so it is needed regularly in the diet.
Riboflavin is found in many of the foods that contain other B-vitamins, but it is not found in high amounts in very many foods. For this reason, dietary deficiency is fairly common, and supplementation may help prevent problems. Brewer's yeast is the richest natural source of vitamin B2. Liver, tongue, and other organ meats are also excellent sources. Oily fish, such as mackerel, trout, eel, herring, and shad, have substantial levels of riboflavin, too. Nori seaweed is a fine source. Milk products have some riboflavin, as do eggs, shellfish, millet and wild rice, dried peas, beans, and some seeds such as sunflower.
Other foods with moderate amounts of riboflavin are dark leafy green vegetables, such as asparagus, collards, broccoli, and spinach, whole or enriched grain products, mushrooms, and avocados. Lower levels of vitamin B2 are found in cabbage, carrots, cucumbers, apples, figs, berries, grapes, and tropical fruits.
Vitamin B2 is sensitive to light, especially ultraviolet light (as in sunlight). Therefore, foods containing even moderate amounts of riboflavin – for example, milk – need to be protected from sunlight. Only a little of the B2 in foods is lost in the cooking water.
Riboflavin is easily excreted out through the urine. Riboflavin is listed in the U.S.P.
The role of Vitamin B2 is largely due to its being the precursor to riboflavin-5'-phosphate and flavin adenine dinucleotide (FAD). These other molecules are extremely important in a host of enzymatic reactions, where they act to carry electrons in energy transferring events. The conversion of riboflavin to these other compounds, critical for the proper function of many biological functions; can be effected by other nutritional factors, hormones, drugs and other disease conditions. The addition of riboflavin-5'-phosphate can help to supplement cases where the conversion of riboflavin is slow.
The US RDA for riboflavin is 1.7mg, although higher levels may support many functions. Supplements with more than 25mg per serving are of little value, as one cannot absorb more than 25mg at any given time.
There are no known toxic reactions to riboflavin, though high doses may cause losses – mainly from the urine – of other B-vitamins. Although quite harmless, Vitamin B2 does make the urine turn bright yellow.
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