The recent publication by Azzi and colleagues puts forth the argument that only -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 -form but include other 2-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 2-forms of α-tocopherol. Furthermore, both -α-tocopherol and the other 2-forms are maintained in human plasma and distributed to tissues and organs, whereas the -stereoisomers are excreted quickly. As such, in recent years the definition of vitamin E including both 2- and -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 -α-tocopherol, again arguing against the restriction of the definition to -α-tocopherol only. Finally, we provide evidence against any safety concerns utilizing the currently accepted definition of vitamin E.

中文翻译：

---

维生素E：不仅仅是单一的立体异构体

Azzi 及其同事最近发表的论文提出了这样的论点：从生理学角度来看，只有 -α-生育酚才应被视为维生素 E。他们的论点主要基于以下断言：只有这种形式已被用于治疗人类严重的维生素 E 缺乏症（称为 AVED，或维生素 E 缺乏性共济失调）。阿齐等人。还认为其他化学性质相似的分子，例如除 α-生育酚和生育三烯酚以外的生育酚，不提供维生素 E 活性。阿齐和他的同事在第二点上是正确的。对维生素 E 的生物活性以及这些活性背后的机制的研究证实，生理维生素 E 活性仅限于某些 α-生育酚形式。然而，同样明显的是，这些活动不仅限于-形式，还包括其他2-形式。事实上，α-生育酚转移蛋白 (α-TTP) 对于介导维生素 E 运输和生物活性以及导致维生素 E 缺乏的遗传缺陷至关重要，它与所有 2 种形式的 α-生育酚都能很好地结合。此外，-α-生育酚和其他2-形式都保留在人血浆中并分布到组织和器官，而-立体异构体则迅速排出体外。因此，近年来，包括 2- 和 -α-生育酚在内的维生素 E 的定义已获得广泛的科学和监管认可。与这种理解相一致，我们提供的证据表明 AVED 确实已通过除 -α-生育酚之外的其他形式成功治疗，再次反对将定义仅限于 -α-生育酚。最后，我们利用当前接受的维生素 E 定义提供了针对任何安全问题的证据。