What Does Zinc Bring to the Table?

Along with other natural supplements like vitamin C, vitamin D and melatonin, zinc is getting a lot of attention for its potential role in supporting immune function during coronavirus infections, and studies are currently underway to evaluate its use in various treatment modalities. Among many others, one study is looking at zinc as part of a combination including an antibiotic, either azithromycin or doxycycline¹; another is evaluating prophylactic combination therapy including vitamin C and zinc in volunteer health care workers.²

Although results of these studies are not yet available, Mahir Ozmen, MD, a professor of surgery at the Istinye University School of Medicine in Istanbul, Turkey and lead researcher in the second study, believes the best treatments for COVID-19 will include zinc and vitamins C and D. Zinc enters and destroys the infected cell, and vitamins C and D support immune function.^{3 4}

Zinc is a mineral and a so-called “essential nutrient” or “essential trace element.” Very small amounts are necessary for human health but it is neither produced by nor stored in the body and must be consistently replenished through the diet.^{5 6} Zinc plays important roles in many of the body’s systems including metabolism of nutrients, growth and repair of body tissues, gene expression, governing the actions of hundreds of enzymes, synthesis of DNA and proteins, wound healing and supporting healthy immune function.⁷

Zinc is a potent antioxidant and anti-inflammatory agent. The second most common mineral in the body, after iron, it is present in every cell.⁸

Benefits of Zinc

Zinc has numerous qualities that make it a useful tool for maintaining health. One of the mechanisms behind its many benefits is activation of T lymphocytes (T cells), which in turn control and regulate immune system responses and act to attack infected or cancerous cells.⁹ It is thought by some researchers that zinc also may decrease the activity of angiotensin-converting enzyme 2 (ACE2), the receptor for SARS-CoV-2, the virus that causes COVID-19.¹⁰

Zinc has been found to treat diarrhea in children, to improve memory and learning ability, promote wound healing, improve male fertility and prevent age-related macular degeneration and other chronic conditions in the elderly.¹¹ It also may have some benefits in treating atopic eczema, psoriasis, acne vulgaris, degenerative retinal lesions, Alzheimer’s disease, attention-deficit hyperactivity disorder (ADHD) and inflammatory bowel disease.¹²

Zinc Has an Established Benefit in Other Coronaviruses

Historically, the mineral zinc has been found to shorten the duration of the common cold, most often caused by one of four coronaviruses, providing a foundation for the hypothesis that zinc also may be useful in the management of COVID-19.

In looking at its benefits in the common cold, the working theory is that zinc “inhibits the binding of the cold virus to cells within the nasal mucosa and suppresses inflammation.” Because there are few available results of zinc in COVID-19 specifically, its benefits in other conditions are evaluated for relevance. For example, one laboratory study from 2010 was able to demonstrate that zinc inhibited the activity and replication of SARS-CoV, the coronavirus strain responsible for an outbreak of SARS-CoV in 2002. Another study done in Spain showed that low zinc levels were predictive of a worse outcome for patients hospitalized with COVID-19.¹³

Foods High in Zinc

By many accounts, oysters are the best food source of zinc, followed by red meat, poultry, and shellfish like crab and lobster. Beans, nuts, whole grains and dairy foods also provide lesser amounts of zinc.¹⁴ Many other foods such as packaged breakfast cereals are fortified with zinc.

Zinc is not as well absorbed from plant-based foods and vegans and vegetarians may need as much as 50 percent more zinc in their diet. It has been suggested that soaking beans in water before cooking them reduces the presence of phytates, which bind to zinc and make it difficult for the body to absorb. Leavened grain products also reduce the level of phytates.¹⁵

A Medical News Today report from 2017 listed the following table comparing foods with the highest reported zinc content¹⁶:

• raw oysters (Pacific), 3 ounces: 14.1 milligrams
• beef, lean chuck roast, braised, 3 ounces: 7.0 milligrams
• baked beans, canned, ½ cup: 6.9 milligrams
• crab, King Alaskan, cooked, 3 ounces: 6.5 milligrams
• ground beef, lean, 3 ounces: 5.3 milligrams
• lobster, cooked, 3 ounces: 3.4 milligrams
• pork loin, lean, cooked, 3 ounces: 2.9 milligrams
• wild rice, cooked, ½ cup: 2.2 milligrams
• peas, green, cooked, 1 cup: 1.2 milligrams
• yogurt, plain, 8 ounces: 1.3 milligrams
• pecans, 1 ounces: 1.3 milligrams
• peanuts, dry roasted, 1 ounces: 0.9 milligrams

Symptoms of Zinc Deficiencies

Referencing the investigations of “consumer advocate, investigator and author Bill Sardi,”¹⁷ Joseph Mercola, DO, notes illness symptoms that may indicate a zinc deficiency. These include but are not limited to dry cough, fever, abdominal discomfort, pneumonia, depressed immune function and loss of sense of smell.¹⁸

Zinc deficiencies are not common in the United States, though the worldwide prevalence is high, estimated at 17 percent of the global population. Many factors can increase risk: Age over 60 years; alcoholism; breastfeeding; cancer or chronic conditions such as diabetes, sickle cell anemia, diarrhea, liver or kidney disease; bowel disorders or recent gastrointestinal surgery all can deplete zinc levels. Vegans and vegetarians also are at greater risk since plant-based foods are not the best sources of bioavailable zinc.¹⁹

Avoid Overdoing Zinc Supplements

Lozenges containing zinc are commonly used at the very first signs of a cold. Nasal sprays are not recommended as many people experience a loss of smell after using them.²⁰

In general, doctors urge caution when taking supplemental zinc products, as too much zinc can cause toxicity issues including nausea, vomiting, loss of appetite, a metallic taste and loss of smell. It also can hinder absorption of copper, potentially causing copper deficiency and anemia, and may have negative interactions with drugs including antibiotics and diuretics.²¹ In addition to affecting copper absorption, too much zinc also may disrupt absorption and metabolism of iron and vitamin A.²²

Many supplements also contain cadmium, another metal that is chemically similar to zinc and often found with it in nature. High levels of cadmium can lead to kidney failure over time. According to Medline Plus, concentrations of cadmium in zinc supplements can vary by as much as 37-fold.²³ Among the many types of zinc supplements available, that same source recommends zinc-gluconate supplements, which consistently contain the lowest cadmium levels. Zinc-rich foods do not cause toxic levels of zinc. According to the U.S. National Institutes of Health (NIH), recommended daily doses of zinc vary by age and gender, as follows²⁴:

• Babies between 0 and 6 months need 2 mg/day (this amount is equivalent to the level of zinc provided by breast milk. Breastfed babies do not need supplemental zinc)
• Babies and children from 7 months to 3 years need 3 mg/day
• Children 4 to 8 years, 5 mg/day
• Children 9 to 13 years, 8 mg/day
• Teens 14 to 18, 11 mg for boys, 9 mg for girls (pregnant teens in that age group need 12 mg/day and lactating teens need 13 mg)
• Over age 19, males need 11 mg/day and females need 8 mg/day, with requirements increasing to 11 mg/day during pregnancy and 12 mg/day during lactation.