”Riboflavin is unique among the water-soluble vitamins in that milk and dairy products make the greatest contribution to its intake in Western diets. Meat and fish are also good sources of riboflavin”
”Biochemical signs of depletion arise within only a few days of dietary deprivation.”
”There is reasonably good evidence that poor riboflavin status interferes with iron handling and contributes to the etiology of anemia when iron intakes are low. Various mechanisms for this have been proposed, including effects on the gastrointestinal tract that might compromise the handling of other nutrients.”
Powers HJ. Riboflavin (vitamin B-2) and health. Am J Clin Nutr. 2003 Jun;77(6):1352-60. doi: 10.1093/ajcn/77.6.1352. PMID: 12791609.