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Oléagineux, Corps Gras, Lipides. Volume 10, Number 3, 165-74, Mai 2003, Colza : enjeux et nouvelles synergies de la recherche, NUTRITION

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Author(s) : Jean‐Marie BOURRE

Summary : "I would try to learn the differences between beechnut, rapeseed, olive, and walnut oils". Honoré de Balzac. "Histoire de César Birotteau". ω3 fatty acids have been more extensively studied in the brain than ω6 or ω9 fatty acids. Alpha‐linolenic acid (18 :3ω3) deficiency alters the structure and function of membranes and induces minor cerebral dysfunctions, as demonstrated in animal models and in human infants. Recent results have shown that dietary alpha‐linolenic acid deficiency induces more marked abnormalities in certain cerebral structures than in others, as the frontal cortex and pituitary gland are more severely affected. These selective lesions are accompanied by behavioural disorders more particularly affecting certain tests (habituation, adaptation to new situations). Biochemical and behavioural abnormalities are partially reversed by a dietary phospholipid supplement, especially ω3‐rich egg yolk extracts or pig brain. A dose‐effect study showed that animal phospholipids are more effective than plant phospholipids to reverse the consequences of alpha‐linolenic acid deficiency, partly because they provide very long preformed chains. Alpha‐linolenic acid deficiency results in disorders of monoaminergic neurotransmission in the rat frontal cortex, but does not affect either the density or the function of dopamine transporters. In alpha‐linolenic acid deficient animals, these disorders of dopaminergic neurotransmission (in the prefrontal cortex, among others) are only partially reversed after correction of the dietary deficiency. Alpha‐linolenic acid deficiency decreases the perception of pleasure by slightly altering the efficacy of sensory organs and by affecting certain cerebral structures. This deficiency modifies the energy metabolism of the brain by altering glucose transport. Age‐related impairment of hearing, vision and smell is due to both decreased efficacy of the parts of the brain concerned and disorders of sensory receptors, particularly of the inner ear or retina. For example, a given level of perception of a sweet taste requires a larger quantity of sugar in subjects with alpha‐linolenic acid deficiency. As ω6 fatty acid deficiency has never been observed, in view of eating habits, its impact on the brain has not been studied. In contrast, ω9 fatty acid deficiency, specifically oleic acid deficiency, induces a reduction of this fatty acid in many tissues, except the brain (but the sciatic nerve is affected). This fatty acid is therefore not synthesized in sufficient quantities, at least during pregnancy‐lactation, implying a need for dietary intake. This review article describes the best sources of ω3 fatty acids and evaluates the degree of enhancement that can be achieved by modifying the food given to animals : a limited effect for ruminants, a substantial effect for pork, rabbit and poultry, and a considerable effect for eggs and fish. The impact on the cover of human nutritional requirements as well as the consequences for human health are discussed. For the first time, the cost for the consumer is specified, by classifying the main foods according to the price of the ω3 fatty acids that they contain.

Keywords : brain, omega‐3 fatty acids