Study: Zinc Supplements May Relieve Cold Symptoms

As cold and flu season arrives, people may be looking for ways to support their immune systems and hopefully keep these illnesses at bay.

According to a new study, zinc supplementation may help prevent cold symptoms and shorten the duration of certain illnesses, regardless of whether a person has a zinc deficiency.

What Is Zinc?

Zinc has gotten a lot of attention in the last year because of its potential role in the treatment of COVID-19. While it's now showing up in supplements, immunity drinks, and many other natural remedies, zinc was believed to play an important role in immune health long before the pandemic started. 

Among the many nutrients that our bodies need to function, there are some natural minerals that are big contributors to our everyday health. Zinc is one such mineral that is naturally found in foods like dairy and soy products, beef, poultry, shellfish, legumes, oysters, fortified breakfast cerals, and whole grains.

Zinc plays many important roles in immunity—from the intracellular killing of harmful pathogens to the production of proteins involved in cell signaling. If a person is deficient for a long time, they may experience chronic inflammation, which can negatively affect immune health.

Can Zinc Prevent or Treat Illness?

Acute viral respiratory tract infections (RTIs) are a common occurrence for some people, especially in the fall and winter. Although there are tried-and-true ways to reduce the risk of getting sick in the first place—like practicing proper hand hygiene and reducing inappropriate antibiotic use—researchers are finding that certain nutrients might be helpful, too.

Studies showing that zinc is important to immune health exist, but there is a knowledge gap about certain aspects of the process, including the mean symptom severity scores around the peak of acute respiratory illness (day 3) and the risks of adverse events.

Systematic reviews of zinc are limited by their variations in administration route or formulation. Plus, many are outdated, have been withdrawn, or are low quality. That's why having a new systematic review and meta-analysis that addresses these concerns is needed.

“It is commonly thought that zinc’s role in preventing and treating infections is only for people who are zinc deficient,” Associate Professor Jennifer Hunter, NICM Health Research Institute at Western Sydney University and a researcher on the study, tells Verywell. “Our findings really challenge this notion.”

The researchers conducted a systematic review and meta-analysis of 28 randomized controlled trials that were focused on the effects of zinc supplementation compared to a placebo in 5,446 participants. 

In the studies that the researchers evaluated, the most common zinc formulations were lozenges followed by nasal sprays and gels containing either zinc acetate or gluconate salts. The daily dose of zinc that was used in the studies included:

• Oral zinc: 15 milligrams (mg) or 45 mg for 7 or 12 months, respectively 
• Sublingual lozenge: between 45 mg and 300 mg daily for up to 2 weeks
• Topical nasal zinc: 0.9 to 2.6 mg per day

Better Than Placebo

After evaluating the data, the researchers found that, among people who did not have a zinc deficiency, zinc appeared to play a positive role in helping them cope with mild to moderate respiratory tract infections.

When compared to a placebo, zinc reduced the risk of developing symptoms consistent with a community-acquired viral respiratory tract infection. The effects were greatest for reducing the risk of developing symptoms like fever.

When zinc was used to treat symptoms consistent with mild to moderate viral respiratory illness, the results showed that, compared to a placebo, there were reductions in day 3 symptom severity. 

Sublingual zinc (which dissolves under the tongue) did not reduce the risk of developing an infection or symptoms of a cold. No significant effects on symptom severity or duration of illness occurred with zinc compared to the use of an active control placebo.

The study's results, which were published in BMJ Open, are promising. However, Hunter says that “there are still a lot of unknowns."

According to Hunter, “at the moment there just isn't enough research to say whether a zinc nasal spray, versus a nasal gel, versus a lozenge, versus oral zinc, is any better or worse than the others."

Hunter adds that "most of the trials used zinc gluconate or zinc acetate formulations, but that doesn’t mean that other zinc compounds are less effective.”

Should You Take a Zinc Supplement?

Adding a zinc supplement to your daily regimen is as simple as buying a bottle and popping a daily pill. However, Hunter cautions that every person may not benefit from supplementation—and could come with risks; for some people "higher doses of zinc taken for a few months can cause copper deficiency.”

Elizabeth Barnes, MS, RDN, LDN, registered dietitian at Weight Neutral Wellness, tells Verywell that “ too much zinc can prevent you from absorbing iron.” She recommends that people do not take an iron supplement at the same time as a zinc supplement.  

For people who are wanting to pursue zinc supplementation, Hunter says that it's important to see “an appropriately trained healthcare professional who can assess your zinc status, recommend a zinc formulation if it is indicated, and then monitor your progress.”

Ultimately, Hunter says that “everybody should focus on optimizing their zinc intake from food and look at ways to improve zinc absorption.” 

If there are true symptoms of a cold or flu, Hunter says that people can “try taking short-term zinc while they are unwell. It might help recover faster and reduce the severity of symptoms. In this context, it is certainly more appropriate than running to the doctor for an antibiotic prescription.”

Naturally Supporting Immune Health

While zinc might be helpful at preventing and treating a common cold, taking supplements does not come without risks. You should know that supplements are not regulated by the Food and Drug Administration (FDA), the quantities vary, and some supplements can interact with medications you might be taking.

Taking a zinc supplement under your healthcare provider’s care and guidance can be one strategy to combat a cold. But Barnes shares the many ways that you can support your immune health naturally.

• Get enough sleep. Barnes stresses improving sleep quality to her clients. "Most of us don't get enough sleep and what we get is poor quality," says Barnes. "I recommend my clients aim for six to nine hours of sleep per night and encourage them to practice good sleep hygiene."
• Eat a balanced diet. "Eating a variety of foods will ensure you have the nutrients you need to support a healthy immune system," Barnes says.
• Exercise. Barnes says that "moving your body with activities that you love is a great way to support your immune system." She recommends moving for at least 150 minutes per week.
• Lower your stress. Barnes suggests daily meditation and deep breathing as potential stress-reducing techniques.