Vitamin B2 — Riboflavin

Vitamin B2 (Riboflavin) is an orange-yellow crystal that is more stable than thiamine. B2 is stable to heat, acid, and oxidation. It is, however, sensitive to light, especially ultraviolet light, as in sunlight. So 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.

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 50 mg. or 100 mg. 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.

Intestinal bacteria produce varying amounts of riboflavin; this poses some questions regarding different people’s needs for B2 and 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.

Sources: 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 also 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.

Functions: Riboflavin functions as the precursor or building block for two coenzymes that are important in energy production. Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) are the two coenzymes that act as hydrogen carriers to help make energy as adenosine triphosphate (ATP) through the metabolism of carbohydrates and fats. Riboflavin is also instrumental in cell respiration, helping each cell utilize oxygen most efficiently; is helpful in maintaining good vision and healthy hair, skin, and nails; and is necessary for normal cell growth.

Uses: Supplemental riboflavin is commonly used to treat and help prevent visual problems, eye fatigue, and cataracts. It seems to help with burning eyes, excess tearing, and decreased vision resulting from eye strain. Riboflavin is also used for many kinds of stress conditions, fatigue, and vitality or growth problems. For people with allergies and chemical sensitivities, riboflavin-5-phosphate may be more readily assimilated than riboflavin. Riboflavin is given for skin difficulties such as acne, dermatitis, eczema, and skin ulcers. B2 is also used in the treatment of alcohol problems, ulcers, digestive difficulties, and leg cramps, and supplementing it may be advantageous for prevention or during treatment of cancer. There is, however, not much published research to support these common uses.

Deficiency and toxicity: There are no known toxic reactions to riboflavin, though high doses may cause losses, mainly from the urine, of other B vitamins. Like most of the B vitamins, deficiency is a much greater concern. Some authorities claim that riboflavin, or vitamin B2, deficiency is the most common nutrient deficiency in America. But because of its production by intestinal bacteria, it may not cause symptoms as severe as other vitamin deficiencies. Insufficient levels of riboflavin are provided by diets that do not include riboflavin-rich foods such as liver, yeast, and vegetables; special diets for weight loss, ulcers, or treatment of diabetes; or the diets of people who have bad eating habits and consume mostly refined foods and fast foods. Riboflavin deficiency is more commonly seen in persons with alcohol problems, in the elderly and the poor, and in depressed patients.

Symptoms of vitamin B2 deficiency include sensitivity or inflammation of the mucous membranes of the mouth; cracks or sores at the corners of the mouth, called cheilosis; a red, sore tongue; eye redness or sensitivity to light, burning eyes, eye fatigue, or a dry, sandy feeling of the eyes; fatigue and/or dizziness; dermatitis with a dry yet greasy or oily scaling; nervous tissue damage; and retarded growth in infants and children. Cataracts may occur more frequently with B2 deficiency. Hair loss, weight loss, general lack of vitality, and digestive problems are also possible with depletion or deficiency states of vitamin B2; these problems may begin when daily intake is 0.6 mg. or less.


Infants0.4—0.6 mg.
Children ages 1—30.8 mg.
Children ages 4—61.0 mg.
Children ages 7—101.4 mg.
Men1.6 mg.
Women1.2 mg.
Pregnant1.5 mg.
Lactating1.7 mg.

Requirements: The RDA of vitamin B2 is based on weight, state of metabolism and growth, and protein and calorie intake. Riboflavin is related closely to energy metabolism. There are only small tissue reserves, and these may be lost when the calculated daily intake is lower than 1.2 mg.

Women who take estrogen or birth control pills, people on antibiotics such as sulfa, and those under stress need additional amounts of riboflavin. Specific amounts must be determined for each individual. Riboflavin may be taken in amounts between 25 and 50 mg. Many B vitamin supplements offer 100 mg. per day, of riboflavin which may be excessive; 10 mg. daily is considered a good insurance level.

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Written by Elson M. Haas MD

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