VITAMIN B2

Riboflavin (vitamin B2), a water-soluble vitamin, was discovered in milk. The name ‘riboflavin’ was given to this vitamin in view of the similarity of a part of its structure to that of the sugar ribose.

Most riboflavin is used immediately and not stored in the body, so excess amounts are excreted in the urine.

Why is vitamin B2 essential for the human body?

Riboflavin is a key component of coenzymes involved with the growth of cells, energy production, and the breakdown of fats, steroids, and medications. It is essential for several oxidation processes inside the cell. It is also concerned with energy and protein metabolism.

What is the recommended daily intake of Vitamin B2?

Several nutritional and physiological factors govern riboflavin requirements. Physical activity reduces urinary riboflavin excretion. Hence, the dietary requirement is increased by exercise and increased physical activity.

The Recommended Daily Allowance (RDA) of vitamin B2 for Indians as per the Indian Council of Medical Research (ICMR) is as follows:

What are the sources of Vitamin B2?

The food sources of riboflavin include: 

Rich sources: Liver, dried yeast, egg powder, and milk powder.

Good sources: Whole cereals, millets, pulses, green leafy vegetables, meat, fish, eggs, milk, oilseeds, and nuts.

Fair sources: Milled cereals and cereal products, roots and tubers, other vegetables and fruits.

What are the signs of deficiency of vitamin B2?

Riboflavin deficiency results in a condition of hypo- or ariboflavinosis. The symptoms of this are

• sore throat
• hyperemia (a condition in which the blood collects in a part of the body)
• oedema of the pharyngeal and oral mucous membranes
• cheilosis (cracking of the corner of the mouth)
• angular stomatitis (inflammation at the corner of the mouth)
• glossitis (inflammation or the infection of the tongue)
• seborrheic dermatitis
• normochromic, normocytic anaemia 

As riboflavin deficiency almost invariably occurs in combination with a deficiency of other B-complex vitamins, some of the symptoms (like glossitis and dermatitis) may result from other complicating deficiencies. 

The major cause of hyporiboflavinosis is inadequate dietary intake due to limited food supply, poor food storage or processing. Children in developing countries are commonly affected. The clinical signs of riboflavin deficiency in children during gastrointestinal infections are prevalent. 

Absorption of riboflavin is also affected in some other conditions, for example, tropical sprue, celiac disease, malignancy and resection of the small bowel, and decreased gastrointestinal passage time. Also, infants receiving phototherapy for neonatal jaundice are at risk of developing a deficiency. People with inadequate thyroid hormone may also demonstrate a lack of the vitamin. 

Can excess vitamin B2 lead to toxicity?

Riboflavin toxicity is not a problem because of the limited intestinal absorption of this vitamin. A toxic level of riboflavin is not observed from food sources and supplements. The gut can only absorb a limited amount of riboflavin at a time, and excess is excreted in the urine.

Bacteria in the large intestine produce free riboflavin that can be absorbed in amounts that depend on the diet. More riboflavin is produced after eating a vegetable-based diet rather than animal-based foods.

An excess of dietary riboflavin, usually from supplements, can cause urine to become bright yellow.

Riboflavin is yellow and naturally fluorescent when exposed to ultraviolet light. Moreover, ultraviolet and visible light can rapidly inactivate riboflavin and its derivatives. Because of this sensitivity, light therapy for prolonged periods in new-borns to treat jaundice or skin disorders can lead to riboflavin deficiency. 

The risk of riboflavin loss from exposure to light is the reason why milk is not typically stored in glass containers instead is sold in cartons or opaque plastic containers to block light.