Nov. 9, 2021 – There’s new evidence that zinc is effective against viral respiratory infections such as colds.

The study, published in BMJ Open, is an extensive analysis of previous studies on the topic. Jennifer Hunter, PhD, of Western Sydney University's NICM Health Research Institute in Australia, and her team reviewed 28 randomized controlled trials (RCTs)..

The trials included 5446 adults who had received zinc either orally, under the tongue or as a nasal spray . The researchers separately analyzed whether zinc prevented or treated respiratory tract infections.

Oral or intranasal zinc prevented five respiratory tract infections RTIs per 100 person-months. There was a 32% lower relative risk of developing mild to moderate symptoms.

Zinc was also associated with an 87% lower risk of developing moderately severe symptoms and a 28% lower risk of developing milder symptoms. The largest reductions in RR were for moderately severe symptoms consistent with an influenza-like illness.

If used early in the course of illness, participants who used zinc under their tongue or as a nasal spray 1.8 times more likely to recover before those who used a placebo.

On the downside, there were more side effects among those who used zinc, including nausea or stomach upset, mouth irritation, or soreness from lozenges. The risk for a serious problem, such as loss of smell or copper deficiency, was low.

Asked to comment, pediatrician assistant professor at the State University of New York Upstate Medical University, says, "It's a very comprehensive review for zinc-related studies in adults."

Imdad also says zinc has "absolutely" been shown to be effective for children with diarrhea. The World Health Organization has recommended it since 2004.

He raised the question of whether it might work similarly in the respiratory tract. Imdad has a long-standing interest in zinc's use in pediatric infections. As for this study, he says, "I think we still need to know the nuts and bolts of this intervention before we can recommend it more specifically."

But both Hunter and Imdad emphasized that zinc is not a game changer. There is a hint that it produces a small benefit in prevention and may slightly shorten the duration of infections More research is needed.

Hunter has received payment for providing expert advice about traditional, complementary, and integrative medicine, including nutraceuticals, to industry, government bodies and nongovernmental organizations and has spoken at workshops, seminars, and conferences for which registration, travel and/or accommodation has been paid for by the organizers. Imdad has disclosed no relevant financial relationships.

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