Vitmain E is a group of chemicals that all share the same biological activity as α-tocopherol and are able to reverse deficiency symptoms. Vitamin E is also an important antioxidant that protects lipid membranes from oxidation. The evidence that vitamin E is protective of cardiovascular disease is controversial. However, the use of synthetic forms of vitamin E, the lack of proper investigation into the relationships between α- and γ-tocopherol as well as other methodological flaws in some research are known problems. In addition, low bioavailability is possible in some individuals and under certain condition. For example, because vitamin E is fat soluble, it is possible that absorption is increased if the α-tocopherol is consumed with foods high in fat. In addition, fortification of foods using industrial techniques may improve the absorbption of some vitamin E compounds.
To investigate the bioavailability of vitamin E researchers1 fed deuterium labelled vitamin E in the form of synthetic d9-all-rac-α-tocopheryl acetate (d9-dl-α-tocopheryl acetate) to 5 healthy subjects. The subjects consumed the vitamin E in either a 400 IU capsule, 41 g of wheat cereal (fortified with 30 IU of vitamin E) or 41 g of wheat cereal (fortified with 400 IU of vitamin E) for 4 days. All treatments were consumed with fat-free milk and blood tests were performed for 72 hours following administration of the treatment After 5 months the subjects consumed a 400 IU capsule with 41 grams of unfortified cereal. The results showed that the vitamin E in the 30 an 400 IU fortified cereal were 6 and 26 times more bioavailable than the vitamin E in the 400 IU capsule.
The results suggest that synthetic vitamin E in the acetate form is more bioavailable when consumed in fortified cereal than when consumed in a capsule. This is probably because the fortification process coats the cereal in a very fine dispersal of vitamin E. When subjects consumed the 400 IU vitamin E capsule with cereal (but not fortified) there was a very large variety in the response of the plasma levels of the subjects. Two subjects showed increases in plasma levels that were significantly higher than when they consumed the 400 IU capsule alone, but 3 subjects showed no increases. Vitamin E occurs in nature in oils as tocopherol (the alcohol) in the d-α- form, but in this study the synthetic acetate ester dl-α-tocopheryl was used. The low subject numbers and questionable selection of vitamin E therefore make interpreting these results problematic.
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