Vitamin B2, also known as riboflavin, is a water-soluble vitamin occurring naturally in those foods in which the other B vitamins exist. Riboflavin is stable to heat, oxidation, and acid although it disintegrates in the presence of alkali or light, especially ultraviolet light.
Riboflavin functions as part of a group of enzymes that are involved in the breakdown and utilization of carbohydrates, fats, and proteins. Riboflavin is necessary for cell respiration because it works with enzymes in the utilization of cell oxygen. It also is necessary for the maintenance of good vision, skin, nails, and hair.
The amount of B2 found in most foods is so little that it normally is quite difficult to obtain a sufficient supply without supplementing the diet. Good sources of riboflavin are liver, tongue, and other organ meats, milk, eggs, and brewer's yeast.
Riboflavin is easily absorbed through the walls of the small intestine. It is then carried by the blood to the tissues of the body and excreted in the urine. The amount excreted depends upon the intake and relative need of the tissues and may be accompanied by a loss of protein from the body. Small amounts of riboflavin are found in the liver and kidneys, but it is not stored to any great degree in the body and therefore must be supplied regularly in the diet.
According to the National Research Council, the daily riboflavin requirements are related to body size, metabolic rate, and rate of growth. These factors are directly related to the protein and calorie intake of the individual. The Recommended Dietary Allowance is 1.6 milligrams for the adult male and 1.2 milligrams for the female. Pregnancy and lactation requirements are 1.5 and 1.7 milligrams, respectively.
There is no known toxicity of riboflavin. However, prolonged ingestion of large doses of any one of the B-complex vitamins, including riboflavin, may result in high urinary losses of other B vitamins. Therefore it is important to take a complete B complex with any single B vitamin.
Deficiency Effects and Symptoms
Riboflavin deficiency may result from one or several of these factors: (1) long-established faulty dietary habits; (2) food idiosyncrasies ("I won't eat liver!"); (3) alcoholism; (4) arbitrarily selected diets for relief of symptoms of digestive trouble; and (5) prolonged following of a restricted diet in the treatment of a disease such as peptic ulcer or diabetes.
The most common symptoms of a lack of B2 are cracks and sores in the corners of the mouth; a red, sore tongue; a feeling of grit and sand on the insides of the eyelids; burning of the eyes; eye fatigue; dilation of the pupil; changes in the cornea; sensitivity to light; lesions of the lips; scaling around the nose, mouth, forehead, and ears; trembling; sluggishness; dizziness; dropsy; inability to urinate; vaginal itching; oily skin; and baldness. A vitamin B2 deficiency can cause some types of cataracts. Experimental studies have shown that some forms of cancer may be related to B2 deficiency.
A lack of stamina and vigor, retarded growth, digestive disturbances and impaired lactation are results of a riboflavin deficiency. Hair and weight losses also frequently result. Underweight persons feeling tense and depressed may need more riboflavin.
Beneficial Effect on Ailments
Riboflavin plays an important role in the prevention of some visual disturbances, especially cataracts. Undernourished women during the end of pregnancy often suffer from conditions such as visual disturbances, burning sensations in the eyes, excessive watering of eyes, and failing vision. These conditions can be helped by supplementing the diet with large doses of B2.
Riboflavin has brought relief to children suffering from eczema. Increased dosages of riboflavin are needed for hyperthyroidism, fevers, stress of injury or surgery, and malabsorption.