Wednesday, September 15, 2021

JAMA posted my comment yesterday on a study reviewing vitamin C and Zinc for Covid-19 patients

JAMA edited my comment and changed the final sentence (adding ‘or some other dose’, which doesn’t make sense), but the gist is there.  

Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical Trial | Complementary and Alternative Medicine | JAMA Network Open | JAMA Network

My original submission:

It is unclear what dose of elemental zinc was used in this study from the text provided. Fifty mg of 'zinc gluconate' is described, but that is 50 mg of a compound that is only about 1/7 elemental zinc. PubChem lists the molecular weight of zinc gluconate at 455.7 and of elemental zinc at 65.4; so zinc gluconate contains about 14.35% elemental zinc (a maximum value since 'as is' measurements include impurities, including moisture). If 50 mg. of ‘zinc gluconate’ was used, as described in the text, it would represent only about 7 mg of actual zinc; not a "high dose" since it would be below the FDA's current (and recently lowered) Daily Value of 11 mg. 

If 50 mg of elemental zinc from a much larger amount of zinc gluconate (typically 350- 400 mg) was used, it should have been described more precisely as that to avoid any confusion. The amount of zinc used was either a low dose erroneously described as a high dose or the authors mistakenly used the compound name (zinc gluconate) in place of the element's (zinc) when describing the 50 mg amount. 

Either way, how the supplement was described in this paper leads inevitably to confusion. The amount of actual zinc should be clearly specified, but the authors did not do so; nor did they relate the amount of this mineral to its RDA, Daily Value, or Upper Limit as a relevant reference point. The implication from the description of a ‘high dose’ is that the amount of zinc was 50 mg, not the amount of zinc gluconate, and that the authors misstated the description of the supplement. But they just as plausibly mistook 50 mg of zinc gluconate for 50 mg of elemental zinc, and then inaccurately described both the supplement and the dosing. 

How did this pass peer review without catching this internal conflict of description that would be obvious to chemists who work with mineral compounds and understand how to appropriately label them by either compound or element? And exactly which dose of elemental zinc was used; 50 mg or 7 mg?

No comments: