Zinc

September 2019

Zinc-rich foods

Which is the Best Zinc Supplement?

Check out our unbiased recommendation of the best products on the market using our rigorous methodology. We screen products for the right formulation, bioavailability, safety, and efficacy to bring you only the best supplements available in 2019.

What You Need to Know About Zinc

If your diet is not rich in red meat and shellfish, then you may not be getting enough zinc from nutrition. Zinc is a mineral that is necessary for many biological processes, including cell reproduction and the proper functioning of enzymes. Zinc also supports a healthy immune system and our senses of smell and taste.[1]

Poor nutrition, a lack of animal protein in one’s diet, alcoholism, malabsorption, and certain chronic medical conditions can cause a zinc deficiency. If you are not getting enough of this critical nutrient from dietary sources, you may want to consider taking a zinc supplement.

Here’s an overview of what you need to know:

  • Zinc is needed for protein production, wound healing, cell division, sexual maturation, and DNA synthesis.
  • The best sources of zinc are red meat and shellfish, especially oysters.
  • Individuals who do not consume much animal protein should increase their zinc intake because the phytic acid naturally found in grains and seeds prevents the absorption of zinc.
  • Hair loss, weight loss, delayed wound healing, chronic infections, and rough skin are signs of zinc deficiency.
  • Poor appetite, depression, and mental lethargy are also symptoms of insufficient zinc levels.
  • The Recommended Dietary Allowance (RDA) of zinc issued by the Food and Nutrition Board is 11 mg per day for men and 8 mg for women. Pregnant women should intake 11 mg of zinc per day, and nursing women should intake 12 mg per day.
  • Low levels of zinc in pregnant women have been linked to low birth weight babies, premature delivery, labor and delivery complications, and congenital anomalies.
  • A lack of zinc can hinder vitamin A absorption, which is needed for reproduction and a healthy immune system.

A Closer Look at Zinc

Zinc is an essential mineral that is mainly found in dietary sources such as red meat and seafood. Zinc is also a main ingredient in over-the-counter cold medicines and throat lozenges.[1] Many people, especially those who do not consume animal products, do not intake sufficient amounts of zinc, which helps the body to fight off bacteria and viruses, heal wounds, and maintain the senses of smell and taste. In order to stay healthy, individuals must ensure that they are getting enough zinc from daily nutrition and/or supplementation.[2]

Why Zinc is Crucial for Health

To maintain optimal health, the body must intake sufficient amounts of zinc, which plays a role in protein production, wound healing, cell division, sexual maturation and reproduction, and DNA synthesis, as well as supporting a healthy immune system.
Zinc is involved in many aspects of cellular metabolism and is an essential functional component of thousands of proteins and cell membranes throughout the human body. More than 300 different enzymes depend on this mineral because of its ability to accelerate crucial chemical reactions.[1, 11]

Zinc ions are a key component of “zinc fingers,” which are proteins that regulate gene expression and act as transcription factors, binding to DNA and influencing the transcription of specific genes.

In multicellular organisms, zinc supports apoptosis, which is a tightly-regulated process of cell death in which cells that are no longer needed or that have become a danger to the organism are destroyed. The regulatory process of apoptosis impacts overall growth and development.[12]

The elements zinc, copper, and selenium are necessary for the synthesis of the thyroid hormones that regulate metabolism, muscle control, brain development, and heart and digestive function. A lack of zinc can lead to hypothyroidism, which causes symptoms such as hair loss. Conversely, thyroid hormones are necessary for zinc absorption; therefore, hypothyroidism can lead to an acquired zinc deficiency.[18]

Zinc also supports normal growth and development during pregnancy, childhood, and adolescence. Healthy brain development requires zinc, specifically for the growth and maturation of neurons, the synthesis of neurotransmitters, and the function of certain brain receptors.
Due to its antioxidant properties, zinc is needed for a properly functioning immune system.[3] Many cells secrete zinc as a signaling molecule, including those found in the immune and nervous systems.
Zinc is also necessary for maintaining the senses of smell and taste. Certain olfactory receptors cannot function without sufficient amounts of this mineral.

Internal Processing of Zinc

Zinc is absorbed in the small intestine and is subsequently distributed via the serum — the protein-rich component of blood that contains disease-fighting antibodies. In serum, zinc binds to several proteins, including transferrin and albumin.[4, 5]

Zinc levels in the human body are closely correlated to zinc intake and loss through the small intestine. Although many zinc transporters and binding proteins have been identified in the cells that line the small and large intestines and the gastrointestinal tract, researchers have not yet catalogued all of the molecules involved in the zinc absorption process. The primary method of maintaining zinc levels is through fluctuations in zinc absorption and intestinal excretion. Excretion occurs through the shedding of epithelial cells and in secretions via the pancreas, liver, gallbladder, and bile ducts.

The human body usually contains up to 3 grams of zinc; almost 90% of it is found in muscles and bones. However, as the body has no specialized mechanism for storing zinc, it excretes whatever it does not need, so daily zinc intake is necessary. Zinc absorption is dependent on the amount of the mineral in the diet and on the specific properties of zinc-containing foods. On average, zinc absorption in humans is about 33%, but some research has shown that individuals who had been fasting were able to absorb between 60% to 70% of dietary zinc when it was administered in liquid form. Absorption was less efficient when the zinc was contained in solid foods.[4, 13]

Zinc Deficiency

Severe zinc deficiencies are rare in North America, but are sometimes diagnosed in countries where malnutrition is widespread.[1, 2, 6]

A zinc deficiency can also be caused by alcoholism, malabsorption, extensive burns, chronic debilitating disorders, and chronic renal diseases. The use of certain drugs, such as penicillamine and diuretics, can sometimes lead to a zinc deficiency. In rare cases, insufficient zinc levels can also be caused by certain genetic disorders, such as acrodermatitis enteropathica, which is characterized by periorificial and acral dermatitis, alopecia, and diarrhea.[2]

A severe zinc deficiency can cause many health conditions and can even be fatal if it is not diagnosed and treated. Symptoms of severe cases include bullous-pustular dermatitis, diarrhea, weight loss, hair loss, and hypothyroidism, as well as emotional disorders.

A moderate zinc deficiency can delay the onset of puberty in adolescents, and can cause symptoms such as rough skin, lack of appetite, mental lethargy, impaired wound healing, taste abnormalities, and impaired night vision.

Mild cases of zinc deficiency can result in oligospermia, a condition characterized by a low sperm count, which is a cause of male infertility.[14] A mild deficiency can also cause hyperammonemia, a potentially fatal metabolic disturbance that results in high levels of ammonia in the bloodstream.

Vegetarians and vegans are vulnerable to zinc deficiencies because red meat and shellfish are the best sources of zinc. Not only is there less zinc in plant-based foods than in animal protein sources, but whole grains and legumes also contain phytic acid that binds to zinc, making it harder for the body to absorb. Due to the complications associated with a plant-based diet, most vegetarians and vegans need to intake 50 percent more zinc than individuals who regularly consume meat.[1, 2, 6]

Older adults are more vulnerable to deficiencies because they have a reduced capacity to absorb zinc. The use of certain medications also increases zinc excretion, such as penicillamine, which is used to treat kidney stones and rheumatoid arthritis; valproate, which is used to treat epilepsy and bipolar disorder and to prevent migraine headaches and seizures; and diuretics, which promote urine production.[16, 17] Those at risk for a zinc deficiency should strive to incorporate more sources of zinc into their diets or take a supplement.

Food Sources of Zinc

Zinc is found in a wide variety of foods. For most Americans, the majority of dietary zinc comes from red meat and poultry. However, oysters are the best source of zinc, as they contain more zinc per serving than any other food.[7] Other good sources include beans, nuts, shellfish, whole grains, fortified breakfast cereals, and dairy products.

Vegetarians can get some of the zinc they need from other sources. Vegetarian-friendly foods that contain zinc include spinach, cremini mushrooms, hemp seeds, pumpkin seeds, sesame seeds, cashews, adzuki beans, lentils, tahini, chickpeas, granola, tempeh, and tofu. However, the amounts of zinc in these foods are substantially lower than the amounts found in red meat and shellfish.

Although vegetarians and vegans can get zinc from grains and seeds, these foods contain phytates (phytic acid). Phytic acid binds with minerals such as zinc, magnesium, calcium, and iron in the intestines, preventing these vital nutrients from being absorbed. Unlike ruminant animals, humans lack phytase, a digestive enzyme that helps to break down phytic acid.[21]

Zinc Supplementation

Individuals who are concerned about intaking enough zinc from food sources alone should consider taking a zinc supplement.[8]

Zinc is absorbed more easily when it is attached to another substance, so many supplements contain chelated zinc. Chelation occurs when organic molecules bond with electrically charged mineral ions. To boost absorption, zinc is chelated with organic and amino acids.[22]

There are many different types of zinc supplements, including zinc gluconate, zinc orotate, zinc sulfate, zinc acetate, zinc picolinate, zinc citrate, zinc glycerate, and zinc monomethionine. The results of one comparative zinc absorption trial indicated that the study participants’ zinc absorption levels rose significantly when they consumed zinc picolinate, which consists of zinc bound to picolinic acid. In contrast, the participants’ zinc levels did not increase significantly after intaking zinc citrate or zinc gluconate, suggesting that zinc absorption is improved when zinc is chelated with picolinic acid.[8] Nevertheless, other studies have suggested that zinc citrate and zinc gluconate are more bioavailable than forms such as zinc oxide.

Research has indicated that many zinc supplements are hard on the stomach. However, zinc citrate is thought to be more digestible than other forms. This may be because a significant portion of the zinc in breast milk is bound to citrate, a naturally-occurring organic acid, so the human body is better equipped to handle supplements containing citrate or other organic acids.[22]

It is important for customers to do their own research before purchasing any kind of supplement. Individuals should look at the source, the manufacturing process, the manufacturer’s reputation, and the molecular form in which it is being sold. Here at HealthAnchor, we apply a scientific approach to evaluating supplements, by analyzing research and data, following industry news, and consulting with experts in order to identify the most effective supplements on the market.

Proper Dosage and Contraindications

Developed by the Food and Nutrition Board (FNB) of the Institute of Medicine of the National Academies, Dietary Reference Intakes (DRIs) provide daily intake recommendations for zinc and other nutrients. Under these guidelines, the Recommended Dietary Allowance for zinc is 11 mg per day for men and 8 mg per day for women. The recommendations increase to 11 mg per day for pregnant women and 12 mg per day for nursing women.[7, 9]

Some experts recommend that pregnant and nursing women who ingest more than 60 mg per day of elemental iron should strongly consider zinc supplementation. Significant intakes of supplemental iron (as opposed to dietary iron) may decrease zinc absorption. Inadequate zinc levels in pregnant women have been linked to medical issues such as low birth weight babies, premature delivery, labor and delivery complications, and congenital anomalies.[10]

The combination of zinc supplements and certain medications, such as the antibiotics tetracycline and quinolone; anticonvulsant drugs, especially sodium valproate; and the bone-strengthening drugs known as bisphosphonates, can reduce both zinc absorption and the effectiveness of the medication.[10] Metal-chelating (binding) agents such as penicillamine, which is used to treat copper overload in Wilson’s disease, and diethylenetriamine pentaacetate (DTPA), which is used to treat iron overload, can cause severe zinc deficiencies.[10] The long-term use of diuretics, also known as water pills, may increase urinary zinc excretion.

A lack of zinc in the human body can have a negative impact on the absorption of other vital minerals and vitamins. For example, a zinc deficiency can inhibit the activities of vitamin A, as zinc is responsible for activating the enzymes that release vitamin A, a fat-soluble vitamin that is necessary for healthy immune and reproductive systems.

It is also important to note that intaking very large quantities of zinc (ie. daily doses of 50 mg or more) for several weeks could lead to a copper deficiency, because zinc and copper have similar absorption patterns. The chronic use of excessive amounts of zinc-containing denture creams can also cause a copper deficiency. To prevent a copper deficiency, the Food and Nutrition Board sets the tolerable upper intake level (UL) for adults at 40 mg of zinc per day, which includes both dietary and supplemental zinc.[10]

Zinc also interacts negatively with calcium and iron. Since they compete for absorption sites within the body, calcium and zinc should not be taken at the same time. It is best to avoid taking a zinc supplement right before or after a meal that contains significant amounts of dairy. Research has also shown that large daily doses of iron can negatively impact zinc absorption. Therefore, to optimize the effectiveness of both supplements, zinc and iron should not be taken at the same time of the day.[2]

Product Selection and Methodology

When choosing a zinc supplement, select a high-quality brand that provides approximately 100% of the Recommended Dietary Allowance.[10] Too much zinc can lead to side effects and toxicities. Single doses of more than 200 mg of zinc are very likely to induce vomiting, and individuals have suffered more mild stomach issues at doses of 50 to 150 mg per day of supplemental zinc.[1]

The consumption of food or beverages contaminated with zinc from galvanized containers could potentially lead to zinc toxicity, which is characterized by symptoms such as abdominal pain, vomiting, diarrhea, and nausea.

When choosing a supplement, ensure that it is “USP Verified, ” which means that the strength, quality, and purity of the product have been established by the testing organization U.S. Pharmacopeia. USP verification is only a small part of our methodology for choosing recommended products.[1] When we make recommendations for supplements, we examine the inventory available on the market. We also look at scientific research, follow cutting-edge industry news, and reach out to experts to ensure that we identify the best and safest products. Reviewing laboratory testing reports, certifications from consumer protection agencies, and even FDA warning letters to companies that have failed to meet manufacturing standards are all part of our methodology. Our evaluation process also includes reviewing supplements to ensure that they contain the doses, formulations, and concentrations promoted on their labels.

Which is the Best Zinc Supplement?

Check out our unbiased recommendation of the best products on the market using our rigorous methodology. We screen products for the right formulation, bioavailability, safety, and efficacy to bring you only the best supplements available in 2019.

References:
1 “Zinc–Fact Sheet for Health Professionals.” National Institutes of Health Office of Dietary Supplements. February 2016. Accessed through: https://ods.od.nih.gov/factsheets/Zinc-Consumer/
2 “Zinc.” Mayo Clinic. Oct. 24, 2017. Accessed through: http://www.mayoclinic.org/drugs-supplements/zinc/background/hrb-20060638
3 “Vitamins and Minerals: What You Should Know About Essential Nutrients.” Mayo Clinic Women’s Healthsource. July 2009. Accessed through: http://www.mayoclinic.org/documents/mc5129-0709-sp-rpt-pdf/doc-20079085
4 Roohani N, Hurrell R, Kelishadi R, Schulin R. “Zinc and its importance for human health: An integrative review.” J Res Med Sci. 2013 Feb; 18(2):144–157. Accessed through: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3724376/
5 Plum L, Rink L, Haase H. “The Essential Toxin: Impact of Zinc on Human Health.” International Journal of Environmental Research and Health. March 2010;7(4):1342–1365. doi: 10.3390/ijerph7041342. Accessed through: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2872358/
6 Prasad AS. “Clinical, endocrinologic, and biochemical effects of zinc deficiency.” Spec Top Endocrinol Metab. 1985;7:45-76. Review. PubMed PMID: 3914098. Accessed through: https://www.ncbi.nlm.nih.gov/pubmed/3914098
7 U.S. Department of Agriculture, Agricultural Research Service. “USDA National Nutrient Database for Standard Reference, Release 24.” Nutrient Data Laboratory. 2011. Accessed through: http://www.ars.usda.gov/ba/bhnrc/ndl
8 Barrie SA, Wright JV, Pizzorno JE, Kutter E, Barron PC. “Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans.” Agents Actions. 1987 Jun;21(1-2):223-8. PubMed PMID: 3630857. Accessed through: https://www.ncbi.nlm.nih.gov/pubmed/3630857
9 Institute of Medicine, Food and Nutrition Board. “Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc.” 2001. Accessed through: https://www.ncbi.nlm.nih.gov/books/NBK222310/
10 King JC, Cousins RJ. Zinc. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins RJ, eds. Modern Nutrition in Health and Disease. 10th ed. Baltimore: Lippincott Williams & Wilkins; 2006:271-285.
11 McCall KA, Huang C, Fierke CA. “Function and mechanism of zinc metalloenzymes.” J Nutr. 2000 May;130(5S Suppl):1437S-46S. Review. PubMed PMID: 10801957. Accessed through: https://www.ncbi.nlm.nih.gov/pubmed/10801957
12 Alberts B, Johnson A, Lewis J, et al. “Programmed Cell Death (Apoptosis).” Molecular Biology of the Cell. 4th edition. 2002. Accessed through: https://www.ncbi.nlm.nih.gov/books/NBK26873/
13 Lönnerdal B. “Dietary Factors Influencing Zinc Absorption.” J. Nutr. 2000 May 1;130(5):1378S-1383S. Accessed through: http://jn.nutrition.org/content/130/5/1378S.full
14 “Low Sperm Count.” Mayo Clinic. July 15, 2015. Accessed through: http://www.mayoclinic.org/diseases-conditions/low-sperm-count/basics/definition/con-20033441
15 “Dietary Supplements.” U.S. Food & Drug Administration. September 5, 2017. Accessed through: https://www.fda.gov/food/dietarysupplements/
16 “Penicillamine (Oral Route).” Mayo Clinic. March 1, 2017. Accessed through: http://www.mayoclinic.org/drugs-supplements/penicillamine-oral-route/description/drg-20065377
17 “Valproic Acid (Oral Route).” Mayo Clinic. March 1, 2017. Accessed through: http://www.mayoclinic.org/drugs-supplements/valproic-acid-oral-route/description/drg-20072931
18 Ambooken B, Binitha MP, Sarita S. “Zinc Deficiency Associated with Hypothyroidism: An Overlooked Cause of Alopecia.” Int J Trichology. 2013 Jan-Mar; 5(1):40–42. doi: 10.4103/0974-7753.114714. Accessed through: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3746228/
19 Vallee BL, Coleman JE, Auld DS. “Zinc fingers, zinc clusters, and zinc twists in DNA-binding protein domains.” Proceedings of the National Academy of Sciences of the United States of America. 1991 Feb 1; 88(3):999–1003. Accessed through: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC50942/
20 King JC, Shames DM, Woodhouse LR. “Zinc homeostasis in humans.” J Nutr. 2000 May;130(5S Suppl):1360S-6S. Review. PubMed PMID: 10801944. Accessed through: https://www.ncbi.nlm.nih.gov/pubmed/10801944
21 Gupta RK, Gangoliya SS, Singh NK. “Reduction of phytic acid and enhancement of bioavailable micronutrients in food grains.” J Food Sci Technol. 2015 Feb; 52(2):676–684. doi: 10.1007/s13197-013-0978-y. PMCID: PMC4325021. Accessed through: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4325021/
22 Lönnerdal B. “Dietary Factors Influencing Zinc Absorption.” Journal of Nutrition. 2000 May 1;130(5):1378S-1383S2000. Accessed through: http://jn.nutrition.org/content/130/5/1378S.full