General:
(1) elderly
(2) chronic alcohol abuse
(3) presence of other vitamin deficiencies
Decreased intake:
(1) starvation, negative nitrogen balance or malnutrition
(2) anorexia
(3) diet low in dairy products, green leafy vegetables, vitamin supplements, riboflavin enriched products, and animal protein
(4) lactose intolerance (due to avoidance of dairy products)
Decreased absorption:
(1) malabsorption
(2) chronic diarrhea
Increased utilization or loss:
(1) heavy exercise
(2) heat stress
(3) systemic infection
(4) drugs (antibiotics, phenothiazines, barbiturates, chlorpromazine, tricyclic antidepressants)
(5) inborn errors of metabolism affecting formation of flavoproteins
(6) phototherapy in newborn infants
