Effect of riboflavin supplementation on riboflavin nutriture of a secondary school population in Nigeria.

Riboflavin status was assessed in 42 secondary school students before and after supplementing the food intake with 5 mg riboflavin daily for 7 days. Energy, protein, and riboflavin intakes were determined on foods actually consumed by each student. Riboflavin nutriture was based on urinary riboflavin excretion and erythrocyte glutathione reductase activity coefficient. The energy and riboflavin intakes of the students were 68 to 82% and 80 to 88%, respectively, of the recommended allowance. The basal urinary riboflavin excretion was 0.335 mg/g creatinine and increased significantly to 3.51 mg/g creatinine after supplementation. The basal erythrocyte glutathione reductase activity coefficient values indicated an overall prevalence of 38% biochemical ariboflavinosis (erythrocyte glutathione reductase activity coefficient greater than 1.30) and dropped significantly (p less than 0.001) from 1.26 to 1.08. The results confirm that urinary riboflavin is of limited value in the assessment of riboflavin status while erythrocyte glutathione reductase activity coefficient more precisely assesses metabolic availability of riboflavin and more accurately detects biochemical ariboflavinosis.