Your body can’t get through a single day without calling on zinc to assist in some absolutely critical tasks. Inside your red blood cells, it helps metabolize carbon dioxide. In your pancreas, it helps store insulin, and in your GI tract, it aids with digestion.
But what about taking zinc for colds? A study in the January 1984 issue of Antimicrobial Agents and Chemotherapy was the first to explore that question.
Taking Zinc for Colds: the Original Research
Researcher George Eby enrolled 146 adults and children in a trial testing whether zinc gluconate lozenges could be useful in treating colds.
For a week, half the participants took a 23-mg zinc lozenge every other waking hour (“after a double initial dose”). The other half took the same number of placebo lozenges.
On average, the adults took 10 lozenges daily, and the children took five. The study’s results were dramatic.
Among the placebo takers who came down with colds, none recovered within 24 hours, and their symptoms continued for an average of 11 days.
Of the zinc-lozenge group, 22 percent (more than one in five) who contracted colds recovered within 24 hours. And 0verall, their symptoms lingered for only four days!
Naturally, such a startling outcome required validation. During the 37 years since the Eby trial, many studies have attempted to duplicate its results. To find what the best balance of evidence says, we’ll turn to systematic reviews which correlated all the best research.
Four Systematic Reviews Looking at Zinc for Colds
–In July 2012, the Canadian Medical Association Journal published a systematic review led by Michelle Science, M.D. of Ontario’s Hospital for Sick Children.
She and her team analyzed the 17 available studies investigating the effectiveness and safety of taking zinc for colds. In total, the studies had included 2,121 participants.
Pitted against those of George Eby’s 1987 trial, the Canadians’ findings were underwhelming. Michelle and her team reported that:
Compared to the various studies’ placebo groups, cold duration was 1.65 days shorter in the zinc-taking adults.
The children in the studies experienced no significant effects from taking zinc for colds.
– In April 2017, the Open Forum Infectious Diseases journal published a review led by Harri Hemilä from the University of Helsinki’s Department of Public Health.
Her team’s goal was to analyze how long it took people taking zinc acetate lozenges to recover from colds. However, only three studies involving 199 participants met their review criteria.
On the day they first felt colds coming on, the participants took either placebos or between 80 and 92 mg of the lozenges. And the data showed that the lozenge taker’s recovery rates were much closer to those of George Eby’s zinc group than those of the Ontario meta-analysis.
The Helsinki review showed that five days into their colds, 70 percent of lozenge takers felt recovered, compared to 27 percent of the placebo takers. But as impressive as zinc’s performance was, it came with a possible catch.
The researchers noted that a daily 80- to 92-mg dose of zinc is 10 times higher than the recommended daily dose of 8 mg for women and 11 mg for men. That said, they also observed that other studies requiring months of daily zinc doses between 100 and 150 mg had resulted in “few adverse effects.”
–An April 2020review examined 10 studies in which participants took lozenges or tablets containing anywhere from 5 to 43 mg of zinc gluconate or zinc acetate every two hours while awake. They concluded that zinc supplementation could reduce colds by an average of 2.25 days.
– A January 2021 review from researchers at Harvard University’s T. H. Chan School of Public Health Department of Nutrition analyzed nine Australian and U.S studies looking at “the effect of zinc supplementation on shortening the duration of common cold…”
The studies included 1038 adults, and all of them reported “significant effects.” For example:
In 91 participants taking 13 mg of zinc every 2 hours while awake, cold symptoms subsided in 2.5 days vs. 3.5 days for the placebo group.
Among 99 U.S. adults, the zinc-supplementing group’s cold symptoms subsided in 3.2 days compared to 7.6 days for the placebo group.
Among 65 U.S. adults, supplementing with zinc led to “a shorter duration of symptoms.” Half of the zinc group were symptom-free in 2.7 days, compared to 7.5 days for the placebo group.
And by the end of one week, 86 percent of the third study’s zinc group were symptom-free, while only 46 percent of the placebo group were!
Considering the research, what can we say about adding zinc to our list of cold remedies? First, that zinc supplements have consistently reduced cold duration. And that, depending on several variables, the reduction can be quite significant.
What remains to be seen is how much zinc we can take for a prolonged period without endangering our health. For that, we’ll need more research – into the potential side effects of exceeding the recommended daily amount of zinc!
I may not consume zinc supplements until I see more research, but I will increase my intake of plant-based foods that are plentiful in zinc. Vegan ingredients high in zinc include hemp seeds, pumpkin seeds, chia seeds, cashews, quinoa, and tofu.
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