Description zinc contributes to the maintenance of normal bones and vision and the normal function of the immune system zinc when ingested forms a complex with picolinic acid which enhances the rate of absorption of zinc the quantity of zinc absorbed is directly related to the availability of picolinic acid which is synthesized from tryptophan if this conversion is impaired or there is a deficiency of vitamin b6 which is required for the conversion then the result will be impaired zinc ab