[Protection of essential fatty acids by vitamin E]

The protective role of vitamin E against free-radical-mediated oxidations is discussed. In spite of the presence of vitamin E in cell membranes, as structural complex with polyunsaturated fatty acids (PUFA) of phospholipids, the question arises whether high PUFA containing diets, producing high deposition of PUFA in the tissues, can nevertheless lead to peroxidations in the body. It has been suggested that large amounts of dietary PUFA increase the requirement for vitamin E and deplete its tissue stores, particularly when PUFA are discontinued in the diet, also because of their longer half-life time than tocopherols. However, in physiological conditions, linoleic acid up to 10% of caloric intake seems to have no effects on vitamin E requirement. In contrast, in essential fatty acid (EFA) deficient animals, also the addition of small amounts of dietary EFA, by resulting in a proportional increase in PUFA content of membrane structural lipids, is associated with an increased need for vitamin E. This becomes particularly important in the case of dietary fish oils or other poorly protected fats.