How Safe is Vitamin E Supplementation?

Abstract

The safety of large doses of vitamin E went virtually unquestioned until the early 2000s, when several studies were published showing that consumption of vitamin E from dietary supplements increased mortality, as well as the risk of gastrointestinal cancer and heart failure. These studies prompted numerous letters to the editors of medical journals and widespread coverage in the media. Both the medical community and the general public became confused and concerned about the use of vitamin E supplements. The purpose of this article is to review the medical literature and to explain these unusual findings. First we provide an overview of the earlier literature on vitamin E. Second, we provide a critical assessment of three meta-analyses that were neutral or negative toward vitamin E supplementation. Third, we review the limitations of meta-analyses in general. Fourth, we assess the individual studies that comprised one of the three meta-analyses. Since all three meta-analyses used many of the same studies, the individual critique should further the understanding of the limitations of these meta-analyses, and the meta-analysis approach in general. Lastly, we offer some guidance for healthcare professionals to give to the general, healthy public and those with chronic conditions who are no doubt left puzzled as to what to do regarding vitamin E supplementation.

Gas chromatography–mass spectrometry microanalysis of alpha- and gamma-tocopherol in plasma and whole blood

“…Besides the absence of accurate analysis of blood levels of supplemented form(s) and other forms present in blood and tissues, all main clinical trials were based on α-TOH supplementation at dosages usually higher than 200 mg/day. It is now emerging that high doses of vitamin E, administered as α-TOH, could interfere with the α-TTP dependent blood transferring and CYP metabolism of minor forms and particularly of γ-TOH, potentially leading to a specific secondary deficit of this form of vitamin E, which may have unfavorable effects in certain diseases [8,41]. In fact, specific biological properties of γ-TOH have been described such as higher efficacy in protecting from the NO-derived species peroxynitrite [3,42] and cell kinase regulation [43], which may explain how the relative abundance in plasma of this form has been associated with the reduced incidence of CHD [10,11] and prostate cancer [12].…”

Green Tea and Vitamin E Enhance Exercise-Induced Benefits in Body Composition, Glucose Homeostasis, and Antioxidant Status in Elderly Men and Women

“…Though one study found that daily dose of 400 IU vitamin E may be deleterious in patients with vascular disease or diabetes mellitus [27], the majority of studies have shown that daily vitamin E supplementation of less than 1000 IU was safe in healthy individuals and may lead to reduced risks of cardiovascular disease, colon and prostate cancers, and poor cognition [28,29]. Furthermore, a dose of 400 IU was efficient in improving cardiovascular parameters [19].…”

Response of seed tocopherols in oilseed rape to nitrogen fertilizer sources and application rates

“…α-Toc exhibits 100% biological activity of vitamin E. β-, γ-, and δ-Toc have only 30%, 15%, and 5% biological activity, respectively (Traber, 2006). Toc confers several human health benefits, including a decreased risk of cardiovascular diseases, improved immune function, and a slower progression of degenerative conditions, such as cataracts, arthritis, and age-related disorders of the nervous system (Traber and Sies, 1996;Pryor, 2000;Bell and Grochoski, 2008). Recent reports suggest that vitamin E (Toc) intake, either from the diet or from supplements, may reduce the risk of liver cancer (Zhang et al, 2012;Hussain et al, 2013a).…”