[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.)