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Your Guide to Zinc

Dr. Kate Rhéaume
Woman applying zinc sunscreen to nose

Zinc is considered one of the most important essential trace minerals for human health, but it doesn’t always get the attention it deserves. [1]

Found throughout the body, especially in the skeletal muscles and bones, zinc is a cofactor in more than 200 enzymatic reactions. Zinc is involved in many physiological processes,such as DNA synthesis cellular growth carbohydrate, protein, and fat metabolism antibody production and insulin storage and secretion. [2,3]

As you can imagine, not getting sufficient zinc daily can impact our overall health. While the recommended intake for zinc is 3 mg per day for children, needs increase to 8 mg per day for adult females and 11 mg per day for adult males. Pregnant and breastfeeding women require higher amounts to support the baby’s normal growth and development.[3]

Insufficient intake, malabsorption, certain medications, and even chronic stress can lead to a deficiency of zinc, impacting the health of the skin, and the gastrointestinal, central nervous, immune, skeletal, and reproductive systems.[4] Consumption of nutrients that reduce zinc’s bioavailability, such as phytic acid, iron, and calcium, may also be a cause.

Zinc levels can be assessed through blood, urine, or hair tests if you are wondering about your zinc levels, speak to your health practitioner for a proper evaluation, especially if you are experiencing common signs and symptoms that may indicate a deficiency including:

  • Loss of hair, taste, or smell
  • Brittle or white-spotted fingernails
  • Loss of appetite
  • Skin concerns
  • Slow growth
  • Impaired immune function
  • Unintended weight loss
  • Poor wound healing

Unfortunately, zinc cannot be stored in the body in significant amounts.[3] Sufficient intake of zinc, either through diet and/or supplementation, can help prevent deficiency and maintain good health. In addition, therapeutic doses of zinc have been researched for specific health concerns such as acne, the common cold, age-related macular degeneration, and immune disturbances. 5] 

Obtaining our nutrients from food sources is always key. When it comes to zinc, consume foods such as fish (oysters contain more zinc per serving than any other food!), plus red meat and poultry, beans and legumes, nuts and seeds, whole grains, and dairy products. But did you know that only 20–40% of the zinc from our food is absorbed into the body? Low bioavailability of zinc from food sources plays an important role in our overall zinc levels. Therefore, using zinc supplements can often help support healthy zinc levels and prevent deficiencies. 

 

Zinc Supplements

Zinc sulfate, zinc citrate, zinc gluconate, zinc bisglycinate…with so many available forms of zinc supplements, choosing one can often be confusing. Why are they so many? As the body cannot efficiently absorb elemental zinc on its own, this mineral is typically attached to another substance to help increase its absorption. Zinc may be attached to inorganic acids, organic acids, or amino acids. Inorganic forms (e.g., zinc sulfate or oxide) are known to be poorly absorbed, but chelated zinc, which is zinc attached to either organic acids (e.g., zinc picolinate, citrate, or gluconate) or amino acids (e.g., zinc bisglycinate or monomethionine), have been shown to have enhanced bioavailability.  

 

 

We can find supplemental zinc in different formats such as lozenges, sprays, liquids, tablets, and capsules. Depending on the delivery method, a specific type of zinc will be used. For example, zinc gluconate is often found in throat lozenges, whereas zinc oxide is typically found in topical products, and zinc citrate and bisglycinate are found in supplements. Learning more about the differences among the various zinc supplements can help you choose the best one for you and your family. 

 

Zinc sulfate and zinc oxide

Supplements with zinc bound to inorganic acids, such as sulfate and oxide, are well known. Zinc sulfate has been used orally to support healthy skin and is commonly found in eye-drop solutions to help with eye irritation. Both zinc sulfate and oxide can be found in topical agents to help with skin conditions such as diaper rashes. [6] Since these forms cause digestive upset and are poorly absorbed, they are generally not recommended in supplement form. Other zinc complexes are better suited due to their enhanced bioavailability. 

Zinc gluconate

Zinc gluconate supplements are formed by combining zinc with the organic acid, gluconic acid. Zinc gluconate has been shown to be well absorbed and seems to be the best form of zinc for seasonal throat and respiratory support, using formats such as lozenges and nasal sprays. [7] There is evidence supporting the use of zinc gluconate lozenges for reducing the symptoms and duration of the common cold. [8,9] One randomized, doubleblind, placebocontrolled clinical trial showed that treatment of the common cold with zinc gluconate lozenges resulted in a significant reduction in the duration of cold symptoms. [8] Patients who received zinc lozenges every 2 hours while they had cold symptoms took 4.4 days to see complete resolution of their condition. However, it took 7.6 days to see symptoms resolve in the placebo group. 

Zinc citrate

Zinc citrate supplements provide zinc chelated with the organic acid citrate, and are known to be well absorbed compared to other forms of zinc. One randomized, double-blind study compared the absorption of 10 mg of zinc citrate, zinc gluconate, and zinc oxide. [9]

Zinc citrate was shown to have an absorption rate of 61.3%, while zinc gluconate and zinc oxide had absorption rates of 60.9% and 49.9%, respectively. The researchers concluded that zinc citrate was as well absorbed as zinc gluconate, and was useful to prevent deficiency. Zinc citrate can be used as a daily zinc supplement to support overall intake.  

Zinc bisglycinate

When zinc is chelated with two molecules of the amino acid glycine, zinc bisglycinate is formed. Zinc bisglycinate is absorbed more efficiently than free zinc ions because of its ability to transport through specialized peptide channels used for protein absorption from the digestive tract. [10] Zinc bisglycinate is more easily absorbed than zinc gluconate. In a randomized, cross-over study, women who supplemented with 15mg of zinc bisglycinate were shown to improve their absorption of zinc into the blood by 43.4% compared to when they took zinc gluconate. [5] Similar to zinc citrate, zinc bisglycinate can be used to support zinc levels and support zinc’s functions in the body. 

Other Zinc Supplements

Zinc picolinate supplements are formed by chelating zinc with the organic acid, picolinic acid. Zinc picolinate may be more easily absorbed than either zinc citrate or zinc gluconate[11] Finally, zinc can also be chelated with hydrolyzed vegetable protein (HVP), often sourced from rice. HVP is broken down into smaller peptides and amino acids to chelate not only with zinc, but with various other minerals, such as magnesium, chromium, and iron, for better absorption. Such supplements are often called Zinc Chelate.

Vegans, vegetarians, older adults, people with digestive disorders, and people who consume alcohol long term are at a greater risk of zinc deficiency. [5,12] In addition to dietary sources, zinc supplements, available as capsules, tablets, lozenges, and liquid, can help protect us against any deficiencies. The typical recommended usage for zinc is 1530 mg per day.

Higher amounts are only advised for short periods of time and for specific purposes that should be discussed with a health care practitioner, as long-term consumption of high amounts of zinc can interfere with copper absorption, leading to copper deficiency. Support and maintain your body’s zinc levels today for a healthy tomorrow. 

ABOUT THE AUTHOR
Dr. Kate Rhéaume
Dr. Rhéaume is a graduate of the Canadian College of Naturopathic Medicine.
References

1.     Institute of Food Technologists (IFT). “Eight ways zinc affects the human body.” ScienceDaily, 2014. Available from: www.sciencedaily.com/releases/2014/07/140718114541.htm 

2.     Grüngreiff K, Reinhold D, Wedemeyer H. The role of zinc in liver cirrhosis. Ann Hepatol. 2016; 15(1):7-16.  

3.     Maxfield L, Shukla S, Crane JS. Zinc deficiency. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 [Updated 2021 Aug 13]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK493231/ 

4.     Roohani N, Hurrell R, Kelishadi R, et al. Zinc and its importance for human health: An integrative review. J Res Med Sci. 2013; 18(2):144-57. 

5.     Gandia P, Bour D, Maurette JM, et al. A bioavailability study comparing two oral formulations containing zinc (Zn bis-glycinate vs. Zn gluconate) after a single administration to twelve healthy female volunteers. Int J Vitam Nutr Res. 2007; 77(4):243-8. 

6.     Gupta M, Mahajan VK, Mehta KS, et al. Zinc therapy in dermatology: A review. Dermatol Res Pract. 2014; 2014:709152. 

7.      Zinc lozenges reduce the duration of common cold symptoms. Nutr Rev. 1997; 55(3):82-5. 

8.    Marshall S. Zinc gluconate and the common cold. Review of randomized controlled trials. Can Fam Physician. 1998; 44:1037-42. 

9.    Wegmüller R, Tay F, Zeder C, et al. Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. J Nutr. 2014; 144(2):132-6. 

10.   Zhang YY, Stockmann R, Ng K, et al. Opportunities for plant-derived enhancers for iron, zinc, and calcium bioavailability: A review. Compr Rev Food Sci Food Saf. 2021; 20(1):652-85. 

11.   Barrie SA, Wright JV, Pizzorno JE, et al. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions. 1987; 21(1-2):223-8. 

12.   Read SA, Obeid S, Ahlenstiel C, et al. The role of zinc in antiviral immunity. Adv Nutr. 2019; 10(4):696-710.