Abstract: Disclosed herein are recombinant hosts comprising at least a first set of chromosomes and a second set of chromosomes, wherein at least one of the first set of chromosomes and the second set of chromosomes comprises a recombinant gene encoding ferritin or a homologue thereof. Also disclosed herein are recombinant hosts comprising a prototroph comprising a recombinant gene encoding ferritin or a homologue thereof. The recombinant hosts may be included in compositions, ingestible items, dietary supplements or pharmaceutical compositions. Also disclosed herein are methods of administering to a subject a composition of the present invention.

Abstract: A method comprising administering to a subject a composition comprising a microbe expressing ferritin or (a) a microbe expressing ferritin and (b) elemental iron, wherein the amount of elemental iron in the composition administered (1) to a subject not diagnosed with an iron deficiency disorder can exceed or is in excess of a dosage of elemental iron recommended by a nutritional authority or (2) to a subject diagnosed with an iron deficiency disorder can exceed or is in excess of a dosage of elemental iron recommended by a medical professional without an adverse effect. A method or a method of altering a composition of a gut bacterial microbiome in a subject comprising administering to a subject a composition comprising of a microbe or host expressing ferritin, with the proviso that when a daily dosage of ferritin in the composition is less than 200 milligrams/day, the composition is free of elemental iron.