Excessive intake of zinc impairs immune responses.

The effect of administration of large amounts of zinc on immune response and serum lipoproteins was examined. Eleven healthy adult men ingested 150 mg of elemental zinc twice a day for six weeks. This was associated with a reduction in lymphocyte stimulation response to phytohemagglutinin as well as chemotaxis and phagocytosis of bacteria by polymorphonuclear leukocytes. Serum high-density lipoprotein concentration decreased significantly and low-density lipoprotein level increased slightly. The common food fad of zinc supplementation with resultant excessive intake could have deleterious effects in healthy persons.