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Linus Pauling Institute
Oregon State University
571 Weniger Hall
Corvallis, OR 97331
E-mail: maret.traber{at}oregonstate.edu
The first chapter of this book covers more than everything you ever wanted to know about the structures, synthesis, and biosynthesis of vitamin E. The next chapter provides the human health implications related to vitamin E and a brief review of the highlights of the new dietary reference intakes for vitamin E developed by the Food and Nutrition Board (1). As a result of the publication of the dietary reference intakes for vitamin E, there is increased awareness in the nutrition community that not all forms of vitamin E are the same and that humans specifically require -tocopherol, a form that is limiting in the diet. Unfortunately, for decades, the contents of vitamin E in foods have been reported in units of -tocopherol equivalents (ATE). ATEs blur the distinction between vitamin E–rich foods and -tocopherol–rich foods. For example, it is shown in Table 8.6 that soybean oil (per 100 g) contains 107 mg ATE but only 8 mg -tocopherol. Chapter 8 provides a listing of the amounts of the various forms of vitamin E in a goodly selection of foods and provides values from different sources, which allows the reader some indication of the variability in measurements. This listing also emphasizes the relative paucity of vitamin E in fruit and vegetables.
Not only are the methods for vitamin E analysis well described and compared in this book, but other factors that influence the dietary content of vitamin E are covered in chapters that focus on vitamin E as a food antioxidant. A rather interesting chapter covers research that has been conducted to investigate the effects of vitamin E supplementation in cows, sheep, pigs, and chicken for the purpose of improving the quality of meat, milk, and eggs. Another "hot" topic that is covered is the stability of vitamin E during food processing, preparation, and storage and how these factors reduce the vitamin E content of some foods. These are important factors given the labile nature of vitamin E and the controversy over how much dietary vitamin E is actually consumed.
My favorite chapter is the one that covers the prooxidant effects of vitamin E. One of the more interesting debates in the vitamin E community concerns the in vivo role of -tocopherol as a prooxidant when coantioxidants are limiting. Oil chemists have been studying these phenomena for decades. Strikingly, as discussed in chapter 3, -tocopherol, but not -tocopherol, becomes a prooxidant at high concentrations (>250 ppm) in oils. Such -tocopherol concentrations are >10 times those found in human plasma or tissues, which suggests that the body limits -tocopherol accumulation. However, this potent antioxidant phenomenon does not explain why -tocopherol concentrations in the body are one-tenth those of -tocopherol. However, the antioxidant power of -tocopherol is clearly beneficial to plants exposed to sunlight and damaging ultraviolet irradiation and is why plants preferentially synthesize high -tocopherol–containing oils. Eitenmiller and Lee are to be congratulated for their interesting and well-written book, which contains an amazingly extensive list of reference citations (>1000).
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