That’s not a Cochrane review? It’s a review in a different journal. The author apparently wrote a paper criticizing a cochrane review on this topic, which was then withdrawn. That’s weird.
I’m not sold on the meta analysis tbh. Publication bias can happen, lots of things can happen, and it’s well within the realm of “aggregate 15 studies of 80 people each” that have not replicated in the past. Especially given the high doses of zinc.
Shouldn’t this be a rec for a N95 instead? Those will probably reduce respiratory viruses much more than 33%
It’s not just personal, in general taking medical advice from reviews in areas you’re not expert in, especially when you haven’t read the review, is probably not great, and as described elsewhere this really doesn’t feel like the sort of thing that would work (compare to magnesium for headache / low energy, which definitely biologically seems somewhat reasonable, although I’m still somewhat iffy on it). That together with personal anecdotes being the sort of thing that Chinese traditional medicine and energy therapy has by bucketloads, and my experience with meta analyses like that regularly falling apart (5-httlpr had a stronger meta analysis with p=0.0001 and four hundred studies, most of which were positive, and then just got executed by a large well done study, https://slatestarcodex.com/2019/05/07/5-httlpr-a-pointed-review/) and priming, with thousands of studies and meta analyses that was also fake and I don’t mean this insultingly because I’ve done this in the past too … a lot … smh … but if you didn’t look closely at the study, it’s probably one of the tens of thousands of bad studies and bad meta analyses that get published so much because so many people want to do them). So I’m pretty confident that the current evidence base for zinc shouldn’t be enough to conclude anything,. And neutral on if it works. But it probably doesn’t because most treatments don’t.
I looked for preregistered trials and found this in 2020 - https://bmjopen.bmj.com/content/10/1/e031662.abstract—preregistration massively helps with both publication bias, post analysis bias, study design, and many other tricks one can do. It found
Results There was no difference in the recovery rate between zinc and placebo participants during the 10-day follow-up (rate ratio for zinc vs placebo=0.68, 95% CI 0.42 to 1.08; p=0.10). The recovery rate for the two groups was similar during the 5-day intervention, but for 2 days after the end of zinc/placebo use, the zinc participants recovered significantly slower compared with the placebo participants (p=0.003). In the zinc group, 37% did not report adverse effects, the corresponding proportion being 69% in the placebo group.
Conclusions A commercially available zinc acetate lozenge was not effective in treating the common cold when instructed to be used for 5 days after the first symptoms. Taste has been a common problem in previous zinc lozenge trials, but a third of zinc participants did not complain of any adverse effects. More research is needed to evaluate the characteristics of zinc lozenges that may be clinically efficacious before zinc lozenges can be widely promoted for common cold treatment.
Which I find much, much more persuasive. Also note the side effect rate and the (admittedly, subgroup, so it is probably meaningless) lower rate of recovery for takers.