What is riboflavin?
Riboflavin or vitamin B2 is an essential enzyme. It is involved in carbohydrate metabolism and facilitates many metabolic reactions in the body. This non-toxic enzyme is important for producing energy in cells, functioning of other enzymes, and normal production of amino acids and fatty acids. Riboflavin is also necessary for the production of glutathione, which is a very important anti-oxidant used by the body for blocking free radical damage.
Sources of Riboflavin
Riboflavin is water-soluble and is obtained through the diet. Milk and other dairy products are the most common sources of riboflavin. Other dietary sources providing riboflavin includes cereals, meats, and dark green vegetables (like asparagus, spinach, and broccoli). Since daily consumption of milk and cereals can provide an adequate amount of riboflavin, a diet deficient in these riboflavin-rich foods can result in riboflavin deficiency. Furthermore, if the glass milk containers are exposed to light, riboflavin may degrade thus reducing its availability from the tainted milk.
Riboflavin requirements are expressed in the terms of recommended dietary allowance (RDA). The RDA for vitamin B2 or riboflavin in children, adults and people with other medical conditions are as follows :
- For infants: 0.3 to 0.6 mg/day
- For children: 0.7 to 1.1 mg/day
- For adolescents: 1.1 to 1.4 mg/day
- For adults:
– 1.3 mg/day for men
– 1.1 mg/day for women
- For pregnant and lactating women:
– Extra 0.1 mg/day in the first trimester
– Extra 0.3 mg/day during the second and third trimesters
– Extra 0.4 mg/day during breast-feeding
- In patients (with normal gastrointestinal absorption): 1 to 4 mg/day
If taken orally, riboflavin is essentially non-toxic and hence dietary overdose does not poset a risk. However, if riboflavin intake is less than the above mentioned RDA for prolonged periods, it can result in riboflavin deficiency.
A deficiency of riboflavin can thus upset many metabolic reactions. Since riboflavin is a water-soluble enzyme, it is not stored in the body. Minute amounts of riboflavin are stored in the liver, kidneys, and heart, and a constant supply is required. Riboflavin deficiency usually occurs with other B-vitamin deficiencies; isolated riboflavin deficiency is rare.
Riboflavin is absorbed in the small intestine and is then transported in the bloodstream with a carrier protein, in the form of a flavin-protein complex. If there is less intake or inefficient absorption of riboflavin, it can result in riboflavin deficiency.
Riboflavin deficiency is more common in pregnant or lactating women, in premature infants undergoing phototherapy for jaundice, in elderly, in depressed persons, and in low-income group people with inappropriate diets.
Riboflavin functions in various enzyme systems in form of two derivatives called riboflavin 5′ phosphate (or flavin mononucleotide [FMN]) and riboflavin 5′ adenosine diphosphate (or flavin adenine dinucleotide [FAD]). FMN and FAD act as coenzymes and they fuse with protein parts of different enzymes (called apoenzymes) to form flavoprotein enzymes. These flavoprotein enzymes help in regulating cellular metabolism, especially carbohydrate, amino acid, or fat metabolism.
Primary and Secondary Deficiency
Riboflavin deficiency can be of two types :
- Primary riboflavin deficiency: Resulting from poor vitamin sources in daily diet
- Secondary riboflavin deficiency: Resulting from conditions that affect riboflavin absorption in the intestine. In such cases, the body may not be able to use the available vitamin. In some patients, there may be an increased excretion of riboflavin from the body.
Signs and Symptoms
Riboflavin deficiency can present following symptoms:
- Scaling and fissures of the lips at the corners of the mouth (cheilosis)
- Sore, red tongue
- Oily and scaly rashes on the skin of scrotum, vulva, and the cleft between the nose and the upper lips
- Cleft lip
- Redness and itching in the eyes
- Night blindness
- Peripheral neuropathy (damage to the peripheral nerves)
- Anemia (due to problems with iron absorption)
- Abnormal changes in the cells on the surface of the cervix (cervical dysplasia)
- Esophageal dysplasia
- Deformed palate
- Growth retardation in infants and children
- Absence of parts of the lower limb (transverse limb deficiency)
- Congenital (by birth) heart defects
- Magenta-colored tongue
- Intolerance to light or photophobia (less common)
Causes and Risk Factors
- Primary riboflavin deficiency:
– inadequate intake of fortified milk, cereals, and other animal products may cause primary riboflavin deficiency.
- Secondary riboflavin deficiency
– chronic diarrhea
– problems with absorption of riboflavin seen with conditions like celiac sprue disease, cancers, and alcoholism
– liver disorders
– kidney or peritoneal dialysis
– chronic alcoholism
– prolonged use of barbiturates and various other drugs may also affect absorption and/or transport of riboflavin
Tests and Diagnosis
A physical examination alone cannot determine riboflavin deficiency with certainty as the lesions resulting riboflavin deficiency are non-specific. The following tests can be used to diagnose riboflavin deficiency:
- Urine sample may be checked for excretion of riboflavin.
- Blood sample can be checked for the activity of an enzyme called glutathione reductase in red blood cells (RBCs). An increased activity of this enzyme indicates a low level of riboflavin.
If some tests indicate deficiency of other enzymes, riboflavin levels should also be checked.
Treatment and Supplements
Treatment of riboflavin deficiency aims at replenishing riboflavin and other B-complex enzymes, the levels of which may also be low. Since riboflavin is readily absorbed from the upper gastrointestinal tract, it is given orally to increase its absorption. Oral route is not preferred in people with absorption problems.
Riboflavin’s gastrointestinal absorption is increased if it is given with food, whereas only about 15% of total riboflavin is absorbed if it is taken alone on an empty stomach. Riboflavin is a water-soluble vitamin and is non-toxic. Therefore excess amounts of orally taken riboflavin surpassing body’s needs are excreted in urine, giving the urine a fluorescent greenish-yellowish color.
- For children aged between 3 to 12 years, daily intake of 3 to 10 mg riboflavin may be given orally.
- For children aged above 12 years and for adults, daily intake of 6 to 30 mg riboflavin may be given orally.
Riboflavin is a photosynthesizing agent and can be destroyed by light. Light, oxygen, and riboflavin can form free radicals, which can result in cataracts. Patients with cataracts are recommended equal to or less than 10 mg of riboflavin daily.