Vitamin E

Not only a single stereoisomer

authored by

M. Eggersdorfer, K. Schmidt, S. Péter, J. Richards, B. Winklhofer-Roob, A. Hahn, U. Obermüller-Jevic

Abstract

The recent publication by Azzi and colleagues puts forth the argument that only RRR-α-tocopherol should be considered as vitamin E from a physiological point of view. They base their argument primarily on the assertion that only this form has been used to treat stark vitamin E deficiency in humans (known as AVED, or Ataxia with Vitamin E Deficiency). Azzi et al. also argue that other chemically similar molecules, such as tocopherols other than α-tocopherol and tocotrienols do not provide vitamin E activity. Azzi and colleagues are correct on this second point. An investigation into the biological activities of vitamin E, and the mechanisms behind these activities, confirms that physiological vitamin E activity is limited to certain α-tocopherol forms. However, it is also clear that these activities are not restricted only to the RRR-form but include other 2R-forms as well. Indeed, the α-tocopherol transfer protein (α-TTP), which is critical to mediate vitamin E trafficking and biological activity, and genetic defects of which lead to vitamin E deficiency, binds well to all 2R-forms of α-tocopherol. Furthermore, both RRR-α-tocopherol and the other 2R-forms are maintained in human plasma and distributed to tissues and organs, whereas the 2S-stereoisomers are excreted quickly. As such, in recent years the definition of vitamin E including both 2R- and RRR-α-tocopherol has gained both broad scientific and regulatory acceptance. Consistent with this understanding, we provide evidence that AVED has indeed been treated successfully with forms in addition to RRR-α-tocopherol, again arguing against the restriction of the definition to RRR-α-tocopherol only. Finally, we provide evidence against any safety concerns utilizing the currently accepted definition of vitamin E.

Organisation(s)

Institute of Food Science and Human Nutrition
Nutrition Physiology and Human Nutrition Section

External Organisation(s)

University of Groningen
University of Tübingen
University of Graz
BASF SE
dsm-firmenich

Type

Article

Journal

Free Radical Biology and Medicine

Volume

215

Pages

106-111

No. of pages

6

ISSN

0891-5849

Publication date

03.2024

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Biochemistry, Physiology (medical)

Electronic version(s)

https://doi.org/10.1016/j.freeradbiomed.2024.02.013 (Access: Closed)