Does Zinc protect you from Covid-19 or boost your immune system?
- Researchers from Spain found that people with lower blood levels of zinc who were admitted to hospital with Covid-19 tended to fare worse than those with healthier levels
- A laboratory study in 2010 showed that zinc inhibited the activity and replication of another coronavirus, SARS-CoV which caused an outbreak in 2002
- Theoretically, sucking zinc lozenges during the early stages of COVID-19 may reduce symptom severity and the duration of the illness, but this has not been proven
- Zinc has been shown to reduce the duration of the common cold
- Zinc deficiency is uncommon in North America; however, certain groups are more at risk
- Zinc supplements should not be taken at too high a dose or for long periods as they can cause toxicity.
Zinc is an essential mineral that our body cannot make itself. This means we have to obtain it from our diet or supplements. Zinc has many important roles in our body, for example, zinc:
- Is responsible for the activity of more than 300 different enzymes in our body
- Is vital for our immune system function including maintaining the integrity of our skin and for cells mediating immunity such as neutrophils and killer cells. Studies have shown people who are deficient in zinc are more susceptible to infection
- Is required for protein and DNA synthesis
- Is important for wound healing
- Supports normal growth and development during childhood, adolescence, and pregnancy
- Ensures the proper functioning of our senses (taste and smell).
What evidence is there to support taking zinc for COVID-19?
There have been hundreds of studies investigating zinc for the common cold. The theory is that zinc could inhibit the binding of the cold virus to cells within the nasal mucosa and suppress inflammation. Although there have been conflicting results, overall, zinc appears to be beneficial in certain forms or circumstances.
Currently, there are few good quality trials investigating the role that zinc supplementation or low zinc levels have in COVID-19 which means we need to review good quality research that looks at zinc in other conditions as well.
- A Cochrane review of 18 studies found zinc lozenges (at least 75mg/day) administered within 24 hours of the onset of symptoms reduced the duration of cold symptoms in healthy people. They could not make a recommendation regarding whether zinc supplementation reduced the risk of developing a cold.
- Zinc gluconate (13.3mg) reduced the symptoms of a common cold by more than three days in 100 employees in Cleveland.
- Zinc was shown to inhibit the activity and replication of another coronavirus (SARS-CoV which caused an outbreak in 2002) in the laboratory.
- Low zinc levels were associated with a poorer outcome in people admitted to a hospital in Spain with Covid-19.
How much zinc do I need?
We have no specialized zinc storage system in our body which means we must take it every day.
The following are the Recommended Daily Allowances (RDAs) for elemental zinc as recommended by the Food and Nutrition Board. Note that high-phytate foods, such as grains, nuts, and legumes, can reduce the absorption of minerals such as zinc.
- Birth to 6 months: 2mg (maximum 4mg)
- Infants and children 7 months to 3 years: 3mg (maximum 5mg to 12 months, 7mg to 3 years)
- Children 4 to 8 years: 5mg (maximum 12mg)
- Children 9 to 13 years: 8mg (maximum 23mg)
- Teenagers 14 to 18 years (girls): 9mg (maximum 34mg)
- Teenagers 14 to 18 years (boys): 11mg (maximum 34mg)
- Adults (women): 8mg (maximum 40mg)
- Adults (men): 11mg (maximum 40mg)
- Pregnant teenagers: 12mg (maximum 34mg)
- Pregnant women: 11mg (maximum 40mg)
- Breastfeeding teenagers: 13mg (maximum 34mg)
- Breastfeeding women: 12mg (maximum 40mg).
What foods contain zinc?
Zinc is present in a wide variety of foods, but it is important to remember that phytates (the major storage form of phosphorous) can bind zinc and inhibit its absorption. Phytates are found in whole-grain bread, cereals, and legumes. This means that zinc contained in grains and plants is not as well absorbed as zinc found in seafood and meat.
Vegetarians should note that foods such as garlic and onions may increase the absorption of zinc from plant foods.
Examples of foods that are high in zinc and the amount of zinc they contain include:
- Oysters 3 ounces: 74mg
- Beef roast 3 ounces: 7mg
- Crab 3 ounces: 6.5mg
- Beef patty 3 ounces: 5.3mg
- Lobster 3 ounces: 3.4mg
- Baked beans ½ cup: 2.9mg
- Fortified breakfast cereal 1 serving: 2.8mg
- Pumpkin seeds 1 ounce: 2.2mg
- Yogurt 8 ounces: 1.7mg
- Cheese, swiss 1 ounce: 1.2mg
- Oatmeal 1 serving: 1.1mg
- Peas ½ cup: 0.5mg.
What are the signs of zinc deficiency?
Zinc deficiency may cause:
- Delayed sexual maturation
- Delayed wound healing
- Eye and skin lesions
- Growth delays
- Hair loss
- Hypogonadism in males or erectile dysfunction
- Impaired immune function
- Loss of appetite
- Taste abnormalities.
Zinc deficiency is difficult to measure in a laboratory because it is tightly contained throughout our body within proteins and nucleic acids. Sometimes zinc deficiency can be present even though laboratory results are normal.
Doctors need to consider a person’s risk factors (such as poor diet, presence of inflammatory bowel disease, alcoholism) together with symptoms of zinc deficiency before determining if zinc supplementation is needed.
Who is at risk of zinc deficiency?
Zinc deficiency in North America is uncommon. The following factors increase the risk of zinc deficiency:
- Age over 60 years
- Breastfeeding women
- Chronic diarrhea
- Chronic liver or kidney disease
- Gastrointestinal surgery
- Infants older than 7 months who are exclusively breastfed
- Inflammatory bowel disorders, such as ulcerative colitis or Crohn’s disease
- Malabsorption syndrome
- Pregnant women with a marginal zinc status to begin with
- Short bowel syndrome
- Sickle cell disease
- Other chronic illnesses.
Vegetarians are at higher risk of zinc deficiency because they do not eat meat or seafood. They may require up to 50% more of the RDA to account for reduced zinc absorption because of the presence of phytates. The following increases the bioavailability of zinc from plant-based foods:
- Soaking beans, seeds, and grains in water for several hours before cooking
- Eating sprouted grains
- Eating leavened grain products, such as bread, rather than unleavened products such as crackers.
When should I consider zinc supplements?
Supplements are NOT recommended for children, because the risk of zinc deficiency is low and zinc toxicity can easily develop. Zinc supplements should only be given to children under medical advice.
For other people, the maximum recommended amounts (see under How much zinc do I need) should not be exceeded long term.
Supplements contain zinc either as zinc acetate, zinc gluconate, or zinc sulfate, and the amount of elemental zinc they contain varies by the salt. For example, zinc sulfate contains 23% of elemental zinc, so a 220mg capsule of zinc sulfate contains 50mg of elemental zinc.
Intranasal zinc supplements should not be used because of numerous reports of anosmia (loss of smell).
Can zinc cause side effects?
Yes. Zinc is a trace mineral which means we need a certain amount of it each day but taking high doses of zinc supplements can cause toxicity.
Side effects of zinc include nausea, vomiting, a loss of appetite, a bad taste, and a loss of smell.
High zinc can also inhibit the absorption of copper, which may result in copper deficiency and anemia.
Zinc supplements may also interact with medicines such as antibiotics, diuretics, and penicillamine.
You cannot over-consume zinc from zinc-containing foods.
- Mossad S, Macknin M, Mendendorp S, et al. Zinc Gluconate Lozenges for Treating the Common Cold: A Randomized, Double-Blind, Placebo-Controlled Study. Annals of Internal Medicine 15 July 1996 https://pubmed.ncbi.nlm.nih.gov/8678384/
- te Velthuis AJW, van den Worm SHE, Sims AC, Baric RS, Snijder EJ, van Hemert MJ (2010) Zn2+ Inhibits Coronavirus and Arterivirus RNA Polymerase Activity In Vitro and Zinc Ionophores Block the Replication of These Viruses in Cell Culture. PLoS Pathog 6(11): e1001176. https://doi.org/10.1371/journal.ppat.1001176
- Shankar AH, Prasad AS. Zinc and immune function: the biological basis of altered resistance to infection. Am J Clin Nutr. 1998 Aug;68(2 Suppl):447S-463S. doi: 10.1093/ajcn/68.2.447S
- Singh M, Das RR. Zinc for the common cold. Cochrane Database of Systematic Reviews 2013, Issue 6. Art. No.: CD001364.
- Wessels I, Rolles B, Rink L. The Potential Impact of Zinc Supplementation on COVID-19 Pathogenesis. Front Immunol. 2020;11:1712. Published 2020 Jul 10. doi:10.3389/fimmu.2020.01712
- Could Zinc Help Fight COVID-19? Drugs.com https://www.drugs.com/medical-answers/zinc-protect-you-covid-19-boost-immune-system-3535446/
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