Significant Discrepancies in “Functional Characterization of Undenatured Type II Collagen Supplements: Are They Interchangeable?”: A Rejoinder

Abstract

In 2021, an article was published comparing two commercial products containing undenatured type II collagen: b-2Cool® (Bioiberica, S.A.U., Barcelona, Spain; designated CII-X, X1, and X2) and UC-II (Lonza Consumer Health Inc, USA; designated CII-Y, Y1, and Y2). However, we feel certain concerns remain where clarification may be warranted.

Keywords:

• Analytical methods
• food supplement
• native collagen
• nutraceutical

This article refers to:

Functional Characterization of Undenatured Type II Collagen Supplements: Are They Interchangeable?

The article (1) concluded that the products were not interchangeable. We thank the authors for declaring their conflicts of interest and further rectifications including the mercury statement in the correction notice (2). The method used to analyze the content of undenatured type II collagen is an undisclosed proprietary ELISA-based method. The use of ELISA-based methods for undenatured type II collagen quantification is highly variable, as shown, for example, in Lugo 2019, (3) where different assay methods detected significantly different amounts of undenatured type II collagen for the same material tested. According to the ELISA-based method, negligible amounts of undenatured collagen were detected in CII-X samples. In contrast, using the methods of analysis based on the European Pharmacopeia (EP § 2.2.56), the content of undenatured type II collagen is 17% for CII-X, 10% for X1, and 23% for X2.

The article includes transmission electron microscopy (TEM) micrographs identifying fibrillar structures characteristic of native collagen in the CII-Y sample but fail to show it in the CII-X. Microscope images are a great resource for proving the presence of certain structures but could be inappropriate to prove its absence. In fact, TEM micrographs of CII-X samples have identified the presence of collagen fibrils as shown in Figure 1.

Figure 1. TEM micrograph (200 nm) showing banded fibrils characteristic of type II collagen in a CII-X sample.

Disclosure statement

Dr. Javier Velasco-Alvarez is Quality and R&D Director at Bioiberica. Bioiberica is the manufacturer of one of the undenatured collagen products analyzed in the article.

Additional information

Funding

This work was supported by Bioiberica SAU.