Zinc and Numbness

The mineral zinc is required in trace amounts to carry out metabolic functions for cell division, protein synthesis, maintenance of immune system health and to support normal growth and development. Excess consumption of zinc through supplements can cause deficiency in the essential mineral copper. The result of copper deficiency may include neuropathy, or nerve damage, causing numbness, paralysis or weakening of targeted body areas.

Zinc Toxicity

The majority of zinc needed to sustain biochemical functions in your body comes from eating a well-balanced diet. You may ingest too much zinc, however, from taking high-dose supplements or consuming contaminated food products stored in galvanized containers. Prolonged consumption of high levels of zinc cause copper deficiency, a mineral copper also required in trace amounts that plays a role in nervous system functions. According to the Linus Pauling Institute, toxic levels of zinc that induce copper deficiency total 60 mg per day and above.

Zinc Toxicity, Copper Deficiency and Neuropathy

Copper deficiency can occur from different factors including poor dietary intake or from diseases resulting in nutrient malabsorption. A 2006 study published in the "American Journal of Clinical Pathology" explored the relationship of excess zinc-induced copper deficiency to investigate pathological implications. The authors found that low copper inhibited proper iron transport thus impacting blood cells and induced peripheral neuropathy in one study subject. Neuropathy damages single or groups of nerves resulting from different causes including direct nerve injury, nutrient deficiency, infection or autoimmune disease. Neuropathy can involve any part of the body including the extremities or involuntary functions like heart rhythm. Numbness, paralysis, tingling and weakness are common symptoms associated with neuropathy.

Zinc and Neuropathy

The exact mechanism of copper deficiency resulting in neuropathy is not fully understood but clinical evidence implicates zinc toxicity as a definitive precipitating factor, notes a 2006 study published in the "American Journal of Neuroradiology." Conversely, animal studies conducted in 1996 and published in the "Proceedings of the Society for Experimental Biology and Medicine" found that zinc deficient study subjects also experience peripheral neuropathy, which includes slowed motor and sensory nerve impulse conduction. No human studies exist as of 2011 to replicate this finding but research is ongoing.

Zinc Intake and Limits

The recommended daily allowance of zinc for adults is 8 to 11 mg and should not exceed the tolerable upper limit intake of 40 mg. You can get adequate zinc from dietary sources including beef, pork, chicken, crab or lobster, which yields 1.8 to 6 mg per serving. Dairy, nuts, beans and whole grains also contain small amounts of zinc ranging from 0.9 to 2 mg per serving. Supplements with zinc vary but consult your physician for recommendations to ensure safety and prevent adverse effects.