Zinc is relatively nontoxic in doses up to 45 mg per day. Doses higher than 150 mg can cause diarrhea, abdominal cramps, and vomiting. High doses can interfere with the body's immune function. Taking doses higher than the recommended level can also interfere with the absorption of copper, another key mineral. This can cause a copper deficiency.
High doses can also reduce iron absorption.
Taking more than the recommended amount of zinc from a supplement has no proven benefits and can cause several risks. Eating lean meat regularly will ensure the proper level of zinc intake. Vegetarians can meet the RDA for zinc by eating a variety of beans, cheese, milk, nuts, seeds, wheat germ, and soy products.