Taking too many zinc supplements all at once can cause nausea, vomiting, cramps, diarrhea and headaches. Taking megadoses of zinc every day for a long period of time can cause problems with copper and iron, damage the immune system and reduce HDL cholesterol levels. Zinc supplements can also interact with certain types of medications.
The U.S. Institutes of Medicine set the daily tolerable upper intake (UL) for vitamins and minerals. The UL is the maximum level you can take every day (from both foods and supplements) that should not cause any health problems.
Daily Tolerable Upper Intakes for Zinc
- Adults: 40 milligrams per day
- Teens: 34 milligrams per day
- Children ages 9 to 13: 23 milligrams per day
- Children ages 4 to 8: 12 millgrams per day
- Children ages 1 to 3: 7 milligrams per day
- Infants ages 7 to 12 months: 5 milligrams per day
- Infants up to 6 months: 4 milligrams per day
Institutes of Medicine, National Institutes of Health. "Dietary Reference Intakes: Elements." Accessed July 16, 2012. http://iom.edu/~/media/Files/Activity%20Files/Nutrition/DRIs/DRI_Elements.pdf.
National Eye Institute, National Institutes of Health. "Age-Related Eye Disease Study--Results." Accessed July 16, 2012. http://www.nei.nih.gov/amd/.
Office of Dietary Supplements, National Institutes of Health. "Dietary Supplement Fact Sheet: Zinc." Accessed July 16, 2012. http://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/.