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.

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.