Isinyithi sisimbiwa esinceda ukwenza iiproteni kunye nee-enzymeskunye nokuhambisa ioksijini emzimbeni wonke. Iipesenti ezingama-70 zifumaneka kwiiseli ezibomvu zegazi, njengenxalenye ye-hemoglobin, nakwi-myoglobin kwiiseli zemisipha.
Zimbini iintlobo zentsimbi: heme kunye non-heme. I-Heme kulula ukuyifumana, kodwa ifumaneka kuphela kukutya okuvela kwimfuyo, njengenyama nentlanzi. Amaqanda, iimbotyi, imifuno, kunye nokunye ukutya okuqinisiweyo kuqukethe uhlobo olungenayo i-heme.
Isibonelelo semihla ngemihla esicetyiswayo samadoda zii-8 milligrams. Isidingo sabafazi siyahluka ngokuxhomekeka ekubeni ngaba yipostmenopausal (8 mg), premenopausal (18 mg), okanye ukhulelwe (27 mg). Imifuno ifuna amaxesha angama-1.8 ngaphezulu kwesinyithi, kuba loo nto ifunyenwe kwimifuno (engekho-heme) ayifumaneki kancinci kunaleyo ifunyenwe kwizilwanyana (heme).
Ukunqongophala kwentsimbi yeyona ngxaki ixhaphakileyo kwezesondlo emhlabeni. Umngcipheko uphezulu ebantwaneni, abasetyhini abakhulelweyo, abasexesheni, kunye nabanikela ngegazi rhoqo. Iimpawu zokuswela i-anemia yentsimbi kukudinwa, isiyezi kunye nentloko ebuhlungu.
Ukugqithiswa kwemaminerali kuyingozi, nangona kunzima ukufikelela kule meko kuphela ngokutya. Isizathu sihlala sifumaneka kwizongezo zentsimbi, yiyo loo nto zingacetyiswa kubantu abadala (abaneemfuno zentsimbi ezisezantsi) okanye abantu abane-hemochromatosis yelifa, imeko ebangela ukuba abantu bayifumane ngakumbi.