[Question] Is this info on zinc lozenges accurate?

Podcast: Zinc Definitely Fights Colds, But You’re Probably Using the Wrong Kind

This podcast claims that zinc lozenges are “probably almost essentially a cure for the common cold”. But there are many caveats:

  • must be zinc acetate or zinc gluconate (but gluconate is strictly worse)

  • use immediately on getting a cold

  • 18mg zinc per lozenge

  • dissolve in mouth 20-30 minutes

  • take every 2 hours

  • must have metallic taste, astringency

  • must free of anything ending -ate (except stearate) or -ic acid; free of magnesium except magnesium stearate (it’s insoluble)

  • only one product on the market satisfies these requirements

The guy sounds to me like he knows what he’s talking about. But I don’t have the technical expertise to really know. (I think I could detect a mediocre bullshitter, but not necessarily a high level one.) If true, it seems like the sort of information that would be good for more people to know; but also like the sort of information that would be more widely known if it were true. (But I can sketch an argument for why it might not.) The research section at the linked page cites three journal articles of which two are open access, but I haven’t looked closely at them.

My own experience is that I got some of these lozenges about a year ago, after reading a transcript of the episode. I thought I’d gotten them too late, but my cold cleared up much faster than I would have expected otherwise. Since then I’ve been trying to collect more anecdotal data, but my body is stubbornly refusing to even start coming down with a cold. Twice I thought it might be, and I took lozenges and didn’t; but I think I took one lozenge on one occasion and three (spaced out) on another, and he thinks they shouldn’t be effective enough for that to have worked. I’m not sure what to make of this, except that it shouldn’t be much given the sample size.

Unfortunately the transcript has now been removed, and I can’t find it on archive.org. I’ve made notes of the first ~35 minutes (of ~70). If someone could take a look (or listen), and say whether it all seems basically accurate, that would be fantastic. Almost all of it seems consistent with what I think I know, with one surprise that I’ve bolded. Apologies for the poor formatting.

  • zinc is important to the immune system in ways that are irrelevant to this. If you aren’t getting enough, you’ll probably benefit from getting more. Good sources are oysters, red meat and cheese.

  • RDA for zinc is satisfied by eating oysters once a week or beef once a day

  • it’s more prevalant and also more bioavailable in animal foods than plant foods. So if you mainly eat a plant diet you may benefit from supplements or zinc-rich foods

  • phytate (grains, nuts, seeds are good sources) is “storage house for minerals”; allows plants to germinate & grow when conditions are right. Phytates make zinc less bioavailable in both the meal and supplements

  • but again this is separate from using zinc to cure colds

  • George Eby’s 3yo daughter with leukemia had many colds, given 50mg zinc gluconate, refused to swallow, cold disappeared

  • Eby and colleagues published RCT in 1984 showing zinc lozenges could reduce median cold duration 5 days mean duration 7 days; basically cures cold

  • Almost every zinc lozenge on the market is useless for this purpose

  • ionic zinc (+ve charge, free not bound to anything) affects nasal tissue and adinoid tissue (lymph tissue in throat) i.e. two major sites of infection during cold: inhibits activation of viral polypeptides that are used in replication of cold virus; inhibit production in our cells of ICAM 1 (intracellular adhesion molecule 1) which is dock that allows virus to grab hold of cell and enter it

  • zinc products are all salts, not ionic. So we need one that releases ionic zinc in the relevant tissues at the right time

  • zinc interferes with replication of virus. So you need to take it almost immediately after being infected or at the first sign of symptoms

  • cold incubation period ~1 day, no symptoms, contagious; 2-3 days where replication and symptoms are increasing; then it peaks and declines, after 5 days basically undetectable but your symptoms may continue. So if you start using them 2-3 days in, they probably won’t do anything

  • tablet or capsule releases zinc into stomach so that’s no good

  • nasal sprays can kill your sense of smell

  • zinc released from a lozenge will reach your nasal tissues and throat tissues

  • some say you want a salt that releases ionic zinc at the pH of saliva. But actually it needs to release at pH of your nasal and throat tissues

  • saliva pH is 5; over 100 times more acidic than pH of cellular environment which is 7.4

  • 7.4 is basic, right? “100 times more acidic than [something on the other side of neutral]” seems like a weird thing to say? It sounds to me like “-5°C is 100 times more freezing than +2°C”. Also, if I google “pH of saliva” I see 6.2 to 7.6. (I wouldn’t be at all surprised to discover I’m just wrong about the acidic/​freezing analogy.)

  • lots of zinc salts release ionic at pH 5, only a handful at 7.4

  • of salts in lozenges, only acetate and gluconate release any meaningful amount

  • at 7.4, gluconate is 50% ionic and acetate is 100% ionic. so zinc acetate should be twice as effective

  • most lozenges are neither; only one is acetate

  • zinc in your mouth has a metallic taste (astringent), dries it out. So people try to make zinc lozenges more palatable

  • but the astringency comes from the ionic zinc in your mouth. So if it’s not astringent, it’s not gonna help.

  • OTOH being astringent doesn’t mean it will help, because that’s in your saliva not your nose/​throat tissues

  • food acids e.g. citrate or tartrate will very tightly bind zinc

  • studies with citrate or tartrate in lozenge seem to suggest it actually makes the cold last longer

  • ionic magnesium delivered to nose/​throat tissues will nullify zinc, increase replication of cold virus

  • one product tested found harmful was produced with very high heat in presence of fats, maybe palm oil; high heat produced insoluble zinc waxes with the fatty acids

  • lubricants used in supplements, like magnesium stearate or other stearates, are insoluble; so they don’t yield an acid that could bind to the zinc and don’t yield much ionic magnesium and don’t cause problems


(Section added 2020-03-09)

I had originally hoped to get some solid confirmation or disconfirmation of the science, and then write up a clearer recommendation post (or not do that, in the case of disconfirmation). That didn’t happen, which is fair enough, but it means I haven’t written that post.

In the meantime, I’ve been linking people here for “why I recommend these lozenges”, and yesterday SSC linked here too. When I wrote it I optimized for “get something out there”, not “include all the information”. That seemed fine when I originally wrote this and didn’t necessarily expect anyone to actually act on it, but now it’s getting more visibility and I’m actively recommending people to act on it.

And in particular, there’s a potentially important safety note included in the half of the podcast that I didn’t make notes on. Probably not a big deal, but still. Potentially.

So: if you take these, you may want to consider copper supplements. From memory: the podcast host thinks it’s probably fine not to, but he does just in case. The ratio of zinc:copper in your bloodstream has a high acceptable range (this says 8:1 − 15:1, and I think the podcast said something similar), and probably most of the zinc in these lozenges isn’t entering your bloodstream anyway.

My honest guess is that you don’t need to worry. I only got some recently, and I’ve only taken one so far. But I think I’ve been remiss not to mention this in writing until now.


By request, I think all of these links are to the correct product:

Life Extension US

Life Extension Europe

Life Extension UK

Amazon UK

Amazon US (The “from the manufacturer” section has a picture of a different product and says something about zinc methionate. But I think the product is correct and that section is just confusing.)