Introduction
Zinc is an essential mineral that plays a crucial role in many bodily functions, including immune function, protein and DNA synthesis, wound healing, and cell signaling and division (Prasad, 1995). Supplements for zinc are available in various forms, such as zinc sulfate, zinc acetate, and zinc gluconate, and can be found in multivitamin/mineral products, cold remedies, and some denture adhesive creams (ODS, 2022).
The recommended daily allowance (RDA) for zinc is 11 mg for adult males and 8 mg for adult females, with higher amounts needed during pregnancy and lactation (Food and Nutrition Board, 2001). While a balanced diet rich in zinc-containing foods, such as oysters, red meat, poultry, beans, nuts, and fortified cereals, should be the primary approach to meeting zinc requirements, certain individuals may be at risk of deficiency. Vegetarians, vegans, and older adults may require zinc supplements due to lower bioavailability of zinc from plant-based foods and increased requirements with age (Saunders et al., 2013).
Zinc supplementation has been associated with various health benefits, including improved immune function, wound healing, and protection against age-related macular degeneration (AMD) (Age-Related Eye Disease Study Research Group, 2001; Hemilä et al., 2017; Wilkinson, 2014). However, it is essential to be aware of potential side effects and interactions associated with zinc supplementation and to consult a healthcare professional before starting any supplement regimen.
Recommended Intakes and Sources of Zinc
The recommended daily allowance (RDA) for zinc varies based on age, sex, and life stage. For adult males, the RDA is 11 mg per day, while for adult females, it is 8 mg per day (Food and Nutrition Board, 2001). Pregnant and lactating women have increased zinc requirements, with the RDA being 11-12 mg and 12-13 mg per day, respectively (Food and Nutrition Board, 2001).
Good dietary sources of zinc include oysters, red meat, poultry, beans, nuts, and fortified cereals. However, the bioavailability of zinc from plant-based foods is lower compared to animal-based foods due to the presence of phytates, which can inhibit zinc absorption (Saunders et al., 2013). As a result, vegetarians and vegans may be at a higher risk of zinc deficiency and may require zinc supplements to meet their daily requirements (Saunders et al., 2013).
Zinc Deficiency and Risk Groups
Zinc deficiency can lead to various health problems, including impaired immune function, delayed wound healing, and growth retardation in children (Prasad, 1995). Groups at risk of zinc deficiency include:
- Vegetarians and vegans (Saunders et al., 2013)
- Pregnant and lactating women (Food and Nutrition Board, 2001)
- Older adults (Prasad, 1995)
- Individuals with malabsorption disorders, such as Crohn’s disease or celiac disease (Siva et al., 2017)
- People with chronic liver or kidney disease (Himoto & Masaki, 2018; Tonelli et al., 2009)
Health Benefits of Zinc Supplementation
Immune Function
Zinc plays a crucial role in the development and function of immune cells (Prasad, 1995). Supplementation with zinc has been shown to reduce the duration and severity of common cold symptoms (Hemilä et al., 2017). A meta-analysis of individual patient data from randomised controlled trials found that zinc acetate lozenges, providing a daily dose of 80-92 mg, reduced the duration of common colds by 33% (Hemilä et al., 2017).
Wound Healing
Zinc is essential for proper wound healing, and deficiency can lead to delayed healing (Wilkinson, 2014). People with chronic wounds or ulcers often have low zinc levels, and supplementation may aid in recovery (Wilkinson, 2014). A Cochrane review found that oral zinc supplementation might improve wound healing in people with venous leg ulcers, although more research is needed (Wilkinson, 2014).
Age-Related Macular Degeneration (AMD)
The Age-Related Eye Disease Study (AREDS) found that a supplement containing zinc, vitamin C, vitamin E, beta-carotene, and copper reduced the risk of advanced AMD by 25% in individuals at high risk (Age-Related Eye Disease Study Research Group, 2001). The AREDS formulation included 80 mg of zinc as zinc oxide, along with other antioxidants (Age-Related Eye Disease Study Research Group, 2001).
Acne
Oral and topical zinc treatments have been shown to effectively reduce acne symptoms (Dreno et al., 2001). A randomised, double-blind, controlled clinical trial found that zinc gluconate (30 mg/day) was as effective as minocycline (100 mg/day) in reducing inflammatory acne lesions over 12 weeks (Dreno et al., 2001). Zinc is thought to decrease inflammation and inhibit the growth of Propionibacterium acnes, a bacteria associated with acne (Dreno et al., 2001).
Childhood Diarrhoea
In developing countries, zinc supplementation has been shown to reduce the duration and severity of acute diarrhoea in children (Lazzerini & Wanzira, 2016). A Cochrane review found that zinc supplementation reduced the duration of acute diarrhoea by around half a day and persistent diarrhoea by around eight hours (Lazzerini & Wanzira, 2016). The World Health Organization and UNICEF recommend zinc supplementation for 10-14 days, along with oral rehydration therapy, for the treatment of acute diarrhoea in children (Lazzerini & Wanzira, 2016).
Safety and Precautions
Adverse Effects and Toxicity
Excessive zinc intake can lead to adverse effects such as nausea, vomiting, loss of appetite, abdominal cramps, diarrhoea, and headaches (ODS, 2022). Long-term high-dose zinc supplementation may also interfere with copper absorption, leading to copper deficiency (ODS, 2022). The tolerable upper intake level (UL) for zinc is 40 mg per day for adults (Food and Nutrition Board, 2001).
Drug Interactions
Zinc supplements can interact with certain medications, such as antibiotics (quinolones and tetracyclines) and penicillamine, a drug used to treat rheumatoid arthritis and Wilson’s disease (ODS, 2022). These interactions can reduce the absorption or effectiveness of the medications. It is essential to consult a healthcare provider before starting zinc supplementation, especially when taking prescription medications.
Importance of Medical Supervision
While zinc supplements can provide various health benefits, it is crucial to consult a healthcare professional before starting any supplement regimen. A healthcare provider can help determine the appropriate dose based on individual needs, assess potential interactions with medications, and monitor for adverse effects. Self-prescribing high-dose zinc supplements without medical supervision may lead to toxicity and other health complications.
Conclusion
Zinc supplements can provide numerous health benefits, particularly for individuals at risk of deficiency, such as vegetarians, vegans, and older adults. Research has shown that zinc supplementation may improve immune function, reduce the duration and severity of common cold symptoms, aid in wound healing, and protect against age-related macular degeneration (AMD). Additionally, zinc has been found to be effective in treating acne and reducing the duration and severity of childhood diarrhoea in developing countries.
However, it is crucial to be aware of the potential side effects and interactions associated with zinc supplementation. Excessive zinc intake can lead to adverse effects such as nausea, vomiting, loss of appetite, abdominal cramps, diarrhoea, and headaches. Long-term high-dose zinc supplementation may also interfere with copper absorption, leading to copper deficiency. Furthermore, zinc supplements can interact with certain medications, such as antibiotics and penicillamine, reducing their absorption or effectiveness. Therefore, it is essential to consult a healthcare professional before starting any zinc supplement regimen to determine the appropriate dose, assess potential interactions, and monitor for adverse effects.
In conclusion, while zinc supplements can be beneficial for certain individuals, a balanced diet rich in zinc-containing foods should be the primary approach to meeting daily zinc requirements. Supplements should be used judiciously and under the guidance of a healthcare provider to ensure safety and effectiveness. By understanding the importance of zinc for overall health and being aware of the potential risks and benefits of zinc supplementation, individuals can make informed decisions about their nutritional needs and work with their healthcare providers to maintain optimal health.
Key Highlights of Learnings and Actionable Tips
- Zinc is an essential mineral involved in many aspects of cellular metabolism, immune function, protein and DNA synthesis, wound healing, and cell signaling and division.
- Zinc deficiency can affect the skin, bones, digestive, reproductive, central nervous, and immune systems. Signs include impaired growth, loss of appetite, and reproductive problems.
- Groups at risk of zinc inadequacy include people with gastrointestinal disorders or who have had bariatric surgery, vegetarians (especially vegans), pregnant and lactating people, older infants who are exclusively breastfed, and people with sickle cell disease.
- Zinc supplements may reduce the duration but not the severity of the common cold when taken shortly after onset of symptoms. Optimal dosage and formulation are unclear.
- Zinc supplementation may help shorten the duration of diarrhea in children in low-income countries.
- Supplements containing zinc and antioxidants may delay the progression of age-related macular degeneration and vision loss.
- The evidence is currently insufficient to determine if zinc supplementation can lower the risk of type 2 diabetes or help manage its complications.
What are some of the best dietary sources of zinc?
Some of the best dietary sources of zinc include:
- Oysters, which contain more zinc per serving than any other food
- Red meat, poultry, and seafood
- Beans, nuts, whole grains, and fortified breakfast cereals
- Dairy products
- Some vegetables like potatoes, green beans, and kale, but in lower amounts
How much zinc do I need per day and what are the upper limits?
The recommended daily allowance (RDA) for zinc varies by age and sex:
- Adult men: 11 mg/day
- Adult women: 8 mg/day (11 mg/day if pregnant, 12 mg/day if lactating)
- Children 4-8 years: 5 mg/day
- Children 9-13 years: 8 mg/day
The tolerable upper intake levels (ULs) for zinc are:
- Adults: 40 mg/day
- Children 4-8 years: 12 mg/day
- Children 9-13 years: 23 mg/day
What forms of zinc are found in supplements and which are best absorbed?
Zinc supplements are available in several forms, including zinc sulfate, zinc acetate, zinc gluconate, and zinc citrate. Absorption of zinc from supplements containing zinc citrate or zinc gluconate is higher (61%) than from zinc oxide (50%).
Can zinc supplements interact with any medications?
Yes, zinc can potentially interact with several medications, including:
- Antibiotics like quinolones and tetracyclines – zinc can decrease their absorption and effectiveness if taken at the same time
- Penicillamine (used for rheumatoid arthritis and Wilson disease) – zinc may reduce its absorption and action
- Thiazide diuretics – these can increase zinc excretion and decrease serum zinc concentrations
Always consult with your healthcare provider about potential interactions between zinc supplements and any medications you take.
Are there any side effects or risks from taking too much zinc?
Yes, excessive zinc intake can cause adverse effects such as:
- Nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, and headaches
- Reduced copper absorption leading to copper deficiency and associated problems like anemia and lowered HDL cholesterol
- Possible reduced magnesium absorption and balance
- Neurological symptoms from long-term overuse of denture adhesives containing zinc
The tolerable upper intake level for adults is 40 mg/day. Avoid taking high-dose zinc supplements unless under medical supervision.
References
Age-Related Eye Disease Study Research Group. (2001). 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. Archives of Ophthalmology, 119(10), 1417-1436. https://doi.org/10.1001/archopht.119.10.1417
Dreno, B., Moyse, D., Alirezai, M., Amblard, P., Auffret, N., Beylot, C., Bodokh, I., Chivot, M., Daniel, F., Humbert, P., Meynadier, J., & Poli, F. (2001). Multicenter randomized comparative double-blind controlled clinical trial of the safety and efficacy of zinc gluconate versus minocycline hydrochloride in the treatment of inflammatory acne vulgaris. Dermatology, 203(2), 135-140. https://doi.org/10.1159/000051728
Food and Nutrition Board, Institute of Medicine. (2001). Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press. https://www.nap.edu/read/10026/chapter/1
Hemilä, H., Fitzgerald, J. T., Petrus, E. J., & Prasad, A. (2017). Zinc acetate lozenges for treating the common cold: An individual patient data meta-analysis. British Journal of Clinical Pharmacology, 83(11), 2285-2293. https://doi.org/10.1111/bcp.13057
Lazzerini, M., & Wanzira, H. (2016). Oral zinc for treating diarrhoea in children. Cochrane Database of Systematic Reviews, 12(12), CD005436. https://doi.org/10.1002/14651858.CD005436.pub5
Office of Dietary Supplements (ODS). (2022). Zinc: Fact sheet for health professionals. National Institutes of Health. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
Prasad, A. S. (1995). Zinc: An overview. Nutrition, 11(1 Suppl), 93-99.
Saunders, A. V., Craig, W. J., Baines, S. K., & Posen, J. S. (2013). Iron and vegetarian diets. The Medical Journal of Australia, 199(S4), S11-S16. https://doi.org/10.5694/mja11.11494
Wilkinson, E. A. J. (2014). Oral zinc for arterial and venous leg ulcers. Cochrane Database of Systematic Reviews, 2014(9), CD001273. https://doi.org/10.1002/14651858.CD001273.pub3
