Zinc is vital for a variety of body functions, and consuming it regularly is essential for optimal health.
What are some of the health benefits of zinc, where do you find it, and how much is too much?
Where is zinc found?
Zinc is found in a variety of foods and supplements.
Some plant-based sources of zinc include legumes, whole grains, beans, nuts, and seeds.1
Although many plant-based foods are good sources of zinc, they may also contain plant compounds called phytates; these may bind to zinc and inhibit its absorption, preventing its health benefits.2
Some animal-derived sources include red meat, oysters, and poultry.
Zinc is also found in dietary supplements in many different forms, including zinc gluconate, zinc acetate, and zinc sulfate.2
It is important to consult a healthcare professional before starting a zinc supplement, as excess zinc levels may interfere with the absorption of other trace minerals such as copper.3
It is important to note that zinc is not readily stored in the body, so it must be consumed regularly through the diet to ensure continual health benefits.2
Zinc is also found in some lozenges and other medications to treat cold symptoms due to their potential benefits for the immune system.
Zinc is also available as a nasal spray; however, these nasal sprays have been shown to either temporarily or permanently impact the senses of taste and smell in a variety of anecdotal reports.4
Zinc can also be found in some skincare products; zinc oxide is often the main active ingredient in mineral sunscreens, and it prevents potentially harmful UV rays from reaching the skin.
Why is zinc important?
Zinc is essential for a variety of processes that occur in the body.
It is a cofactor – an essential molecule that helps enzymes function – for over 300 major biochemical reactions.5
Zinc is important for the function of thymulin, which is a hormone that helps in the maturation of T-cells.6 T-cells are an important part of the adaptive immune system, which recognizes and eliminates known and familiar pathogens.
Zinc is particularly important for cell growth and division because it helps DNA replication, cell signaling, and cellular metabolism.7
What is the RDA for zinc?
The Recommended Dietary Allowance (RDA) for zinc for those above 18 years of age is 11 milligrams (mg) for males, 8mg for females, and 11mg and 12mg for pregnant and lactating females, respectively.
The RDA for those between 14 and 18 years of age is 11mg for males, 9mg for females, and 12mg and 13mg for pregnant and lactating females, respectively.2
The RDA for zinc is 8mg for children between nine and thirteen years, 5mg for children between four and eight years, and 3mg for children between seven months and three years of age.
The RDA for zinc for infants under seven months of age is estimated to be around 2mg, which is the average intake for healthy, breastfed babies.2
These values are given by the National Institutes of Health (NIH), and the RDA represents the daily intake sufficient to meet the dietary needs of 97 to 98 percent of healthy individuals.2
For reference, three ounces of cooked oysters provide 673 percent of the RDA for zinc, one-half cup of baked beans provides around 26 percent of the RDA, and one ounce of pumpkin seeds provides about 20 percent of the RDA.2
How much is too much?
The daily Upper Limit (UL) for zinc is 40mg for those above 18 years of age, 34mg for those between 14 and 18 years of age, 23mg for those between nine and thirteen years of age, 12mg for those between four and eight years of age, 5mg for those between seven and twelve months of age, and 4mg for infants under seven months of age.2
These values are given by the NIH, and the UL represents the maximum daily intake that is unlikely to cause adverse health effects.2
Some side effects of acute zinc toxicity, which may occur with the consumption of extremely high amounts of zinc, may include nausea, vomiting, and fatigue.8
Zinc toxicity can also happen when excessive intakes of zinc are consumed for an extended period of time; some side effects of long-term zinc toxicity may include copper and iron deficiencies, decreased immune function, and an altered blood lipid profile with respect to levels of high-density lipoprotein (HDL) and low-density lipoprotein (LDL).8
Zinc can also interact with a variety of medications.
For example, zinc could potentially reduce the activity of quinolone antibiotics such as levofloxacin and tetracycline antibiotics such as doxycycline and minocycline.2,9
This could potentially lead to improper treatment of bacterial infections and the development of antibiotic-resistant bacteria.
It is important to tell your doctor or pharmacist about any supplements that you may be taking in order to reduce the risk of these side effects.
What are the health benefits of zinc?
Getting enough zinc could potentially help prevent the negative impacts on the immune system associated with zinc deficiency, and this may help ensure that the body’s natural defense against pathogens stays strong.10
There is some evidence suggesting that zinc may help heal wounds such as leg ulcers, but these findings were observed in small studies and more research is needed to confirm the validity of these findings.11
Finally, some research suggests that one of the health benefits of zinc in combination with antioxidants might be to help prevent the progression of severe age-related macular degeneration (AMD).
One study of over 4000 participants in the Netherlands found that increased dietary consumption of both zinc and vitamin E was associated with a lower rate of AMD.12
Another study of roughly 3500 participants found that lower rates of advanced AMD were observed in the group taking zinc in combination with an antioxidant supplement containing 500mg of vitamin C, 400 IU of vitamin E, and 15mg of beta-carotene.13
More research is needed to confirm the significance of these findings, as well as how these potential benefits can be optimized.
Zinc deficiency
Isolated zinc deficiency is relatively uncommon in developed countries; however, when it occurs, it often presents with a variety of non-specific side effects.
For this reason, it is important to consult with your doctor to ensure that a zinc deficiency is causing the symptoms.
Some side effects of zinc deficiency may include appetite loss, reduced immune function, hair loss, diarrhea, impotence, skin lesions, fatigue, and more.2 Â Â
Some groups may be at a higher risk of zinc deficiency than others.
People who follow vegetarian or vegan lifestyles may be at an increased risk of zinc deficiency as some of the zinc found in plant foods may bind to phytates, which reduces its bioavailability preventing the health benefits of zinc.14
Some cooking techniques, such as soaking beans and seeds, may help prevent this.
Infants above seven months of age that exclusively breastfeed may be at risk of zinc deficiency due to their increased zinc needs.2,15
For the same reason, pregnant and lactating women may also be at an increased risk of zinc deficiency, so it is important to routinely check in with your healthcare provider regarding your and your infants’ zinc levels.
Zinc deficiency tends to be a common occurrence in people with sickle cell disease, as a variety of the symptoms of sickle cell disease may potentially lead to increased zinc needs.16
People with impaired absorption of zinc may be at an increased risk of zinc deficiency.
These at-risk populations may include people with ulcerative colitis, Crohn’s disease, and chronic alcoholism, among others.2
Zinc supplementation
Zinc deficiency is generally treated with zinc supplementation that exceeds the RDA, and your healthcare provider would determine the exact dosage and treatment course based on the severity of the deficiency and other individual factors.17
Zinc deficiency may also be prevented by consuming adequate amounts of zinc through food or supplementation.
If you think you have a zinc deficiency or are at an increased risk, consider getting your blood levels tested.
As always, consult your doctor before you begin taking any vitamin or mineral supplement to make sure your medications or health conditions don’t make it a serious risk.
References:
1) The Nutrition Source (n.d.) Zinc. Harvard T.H. Chan School of Public Health. Accessed 2021, March 7, from https://www.hsph.harvard.edu/nutritionsource/zinc/
2) National Institutes of Health: Office of Dietary Supplements (2020, July 15). Zinc: Fact Sheet for Health Professionals. National Institutes of Health. Accessed 2021 March 7, from https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
3) Osredkar, J., Sustar, N. (2011). Copper and Zinc, Biological Role and Significance of Copper Imbalance. Journal of Clinical Toxicology S:3. doi: 10.4172/2161-049S:S3-001
4) Jafek, J.W., Linschoten, M.R., Murrow, B.W. (2004). Anosmia after intranasal zinc gluconate use. Am J Rhinol 18(3): 137-141. Retrieved online from https://pubmed.ncbi.nlm.nih.gov/15283486/
5) Rink, L., Gabriel, P. (2000, November). Zinc and the immune system. Proc Nutr Soc 59(4): 541-552. Doi: 10.1017/s0029665100000781
6) Prasad, A.S. (1995). Zinc: An overview. Nutrition 11(1): 93-99. Retrieved online from https://pubmed.ncbi.nlm.nih.gov/7749260/
7) MacDonald, R.S. (2000 May 1). The Role of Zinc in Growth and Cell Proliferation. The Journal of Nutrition 130(5): 1500S-1580S. Doi: 10.1093/jn.130.5.1500S
8) Fosmire, G.J. (1990, February). Zinc toxicity. American Journal of Clinical Nutrition 51(2): 225-227. Doi: 10.1093/ajcn.51.2.225
9) Lomaestro, B.M., Bailie, G.R. (1995 May). Absorption interactions with fluoroquinolones. 1995 update. Drug Saf 12(5): 314-333. Doi: 10.2165/00002018-199512050-00004.
10) Shankar, A.H., Prasad, A.S. (1998 August). Zinc and immune function: the biological basis of altered resistance to infection. American Journal of Clinical Nutrition 68(2): 447S-463S. Doi: 10.1093/ajcn/68.2.447S
11) Lin, P., Sermersheim, M., Li, H., et al (2018 January). Zinc in Wound Healing Modulation. Nutrients 10(1): 16. Doi: 10.3390/nu10010016.
12) Van Leeuwan, R., Boekhoorn, S., Vingerling, J.R., et al (2005, December 28). Dietary intake of antioxidants and risk of age-related macular degeneration. JAMA 294(24): 3101-3107. Doi: 10.1001/jama.294.24.3101
13) Age-related eye disease study research group (2001 October). A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta-carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no.8. Arch Opthalmol 119(10); 1417-1436. Doi: 10.1001/archopth.119.10.1417.
14) American Dietetic Association; Dietitians of Canada (2003 June). Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets. J Am Diet Assoc 103(6): 748-765. Doi: 10.1053/jada.2003.50142.
15) Krebs, N.F. (1998 August). Zinc supplementation during lactation. Am J Clin Nutr 68(2): 509S-512S. Doi: 10.1093/ajcn.68.2.509S
16) Prasad, A.S. (2002 February). Zinc deficiency in patients with sickle cell disease. The American Journal of Clinical Nutrition 75(2): 181-182. Doi: 10.1093/ajcn.75.2.181.
17). Saper, R.B., MD, MPH; Rash, R., MA. (2009, May 1). Zinc: An Essential Micronutrient. American Family Physician 79(9): 768-772. Retrieved online from https://www.aafp.org/afp/2009/0501/p768.html
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