Vitamin B2

Chemistry:

water-soluble vitamin, also called riboflavin, is composed of a sugar "ribose" and flavin which gives it the yellow color. It is part of coenzymes flavinadenine mononucleotide (FAD) and flavin mononucleotide (FMN) hence plays a key role in oxidative metabolism (energy metabolism).


Sources:

Milk and other dairy products, cereals, meats,liver, eggs, legumes, almonds and dark green vegetables (eg, spinach, asparagus, and broccoli).


Daily allowance:

The recommended nutrient intake (RNI) of riboflavin is 0.6 mg/5000 kJ daily. The daily RNI ranges are as follows:

Infants

• 0 - 6 months: 0.3* milligrams per day (mg/day)
• 7 - 12 months: 0.4* mg/day

*Adequate Intake (AI)

Children

• 1 - 3 years: 0.5 mg/day
• 4 - 8 years: 0.6 mg/day
• 9 - 13 years: 0.9 mg/day

Adolescents and Adults

• Males age 14 and older: 1.3 mg/day
• Females age 14 to 18 years: 1.0 mg/day
• Females age 19 and older: 1.1 mg/day

 

Oral riboflavin doses of 1-4 mg daily are usually considered sufficient as a nutritional supplement in patients with normal GI absorption. These doses should be present in the normal diet.
Recommended increased requirements for pregnant and lactating women are as follows:

• Additional 0.1 mg/day in the first trimester
• Additional 0.3 mg/day in the second and third trimesters
• Additional 0.4 mg/day during lactation

 The recommended amounts are 1.4 mg per day for pregnant women and 1.6 mg per day in breast-feeding women.

 

 

Causes of vitamin B2 deficiency:

 

1-Malnutritin

2-Alcoholism

3-Diarrhea

4-Irritable bowel syndrome

5-Lactose intolerance

6-Malabsorptive states (eg, celiac disease, small bowel resection, tropical sprue, inflammatory bowel disease)

7-Pregnancy and lactation (secreted in milk)

8-Inborn errors of riboflavin metabolism

9-It may develop in patients with diabetes, cardiac diseases and cancer.

 

 

Clinical presentation, signs and symptoms of vitamin B2 deficiency:

 

1-Cheilosis (cracking and inflammation of lips)

2-Angular stomatitis (cracking and inflammation of the angles of the mouth)

3-Glossitis (swollen, deep-red tongue)

4-Seborrheic dermatitis (greasy, scaled lesions most commonly on the face, calp, scrotum, vulva, and philtrum)

5-Interstitial keratitis with potential opacification and ulceration of the cornea

6-Corneal neovascularization

7-Night blindness

8-Cataracts

9-Normocytic normochromic anemia

10-Migraine headaches

11-Peripheral neuropathy

12-Fatigue

13-Esophageal and/or cervical dysplasia

14-Retarded growth in infants and children

15-Birth defect (eg, cleft lip/palate, congenital heart defects, transverse limb defeciency TLD)

 

Riboflavin deficiency is classically associated with the oral-ocular-genital syndrome. Angular cheilitis, photophobia, and scrotal dermatitis are the classic remembered signs.

 

Laboratory findings and workup:

 

Measurement of red blood cell glutathione reductase activity may help in the detection of riboflavin deficiency. An increase in the stimulation of this enzymatic reaction confirms a low level of riboflavin. Erythrocyte glutathione reductase activity assay, expressed as a ratio of results with and without added flavin adenine dinucleotide. A ratio of 1.3 or more indicates functional vitamin B2 deficiency, while a ratio of less than 1.3 indicates adequate levels.
Riboflavin can cause false elevations of urinary catecholamines and false-positive urine urobilinogen reactions (Ehrlich test).
 If urinary riboflavin excretion is <19 µg/g creatinine (without recent riboflavin intake) or < 40 µg per day are indicative of deficiency.

Treatment:

Dosages of riboflavin for deficiency treatment are as follows:

• Age < 3 years: not established
• Age 3-12 years: 3-10 mg PO divided daily
• Age >12 years: Administer as in adults (see below)
• Adult dose: 6-30 mg PO divided daily for replacement when deficiency is suspected