Plourde Mélanie, Cunnane Stephen C
Research Center on Aging, Departments of Medicine, and Physiology and Biophysics, Université de Sherbrooke, 1036 Belvedere St, South, Sherbrooke, QC J1H 4C4, Canada.
Appl Physiol Nutr Metab. 2007 Aug;32(4):619-34. doi: 10.1139/H07-034.
There is considerable interest in the potential impact of several polyunsaturated fatty acids (PUFAs) in mitigating the significant morbidity and mortality caused by degenerative diseases of the cardiovascular system and brain. Despite this interest, confusion surrounds the extent of conversion in humans of the parent PUFA, linoleic acid or alpha-linolenic acid (ALA), to their respective long-chain PUFA products. As a result, there is uncertainty about the potential benefits of ALA versus eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA). Some of the confusion arises because although mammals have the necessary enzymes to make the long-chain PUFA from the parent PUFA, in vivo studies in humans show that asymptotically equal to 5% of ALA is converted to EPA and <0.5% of ALA is converted to DHA. Because the capacity of this pathway is very low in healthy, nonvegetarian humans, even large amounts of dietary ALA have a negligible effect on plasma DHA, an effect paralleled in the omega6 PUFA by a negligible effect of dietary linoleic acid on plasma arachidonic acid. Despite this inefficient conversion, there are potential roles in human health for ALA and EPA that could be independent of their metabolism to DHA through the desaturation - chain elongation pathway.
人们对几种多不饱和脂肪酸（PUFA）在减轻心血管系统和大脑退行性疾病所导致的重大发病率和死亡率方面的潜在影响极为关注。尽管有这种关注，但对于母体PUFA，即亚油酸或α-亚麻酸（ALA）在人体内转化为其各自长链PUFA产物的程度仍存在困惑。因此，关于ALA与二十碳五烯酸（EPA）或二十二碳六烯酸（DHA）的潜在益处存在不确定性。部分困惑的产生是因为尽管哺乳动物拥有从母体PUFA合成长链PUFA所需的酶，但人体的体内研究表明，ALA渐近地仅有约5%转化为EPA，且<0.5%的ALA转化为DHA。由于在健康的非素食人群中这条途径的能力非常低，即使大量摄入膳食ALA对血浆DHA的影响也可忽略不计，在ω-6 PUFA方面，膳食亚油酸对血浆花生四烯酸的影响同样可忽略不计。尽管这种转化效率低下，但ALA和EPA在人类健康中可能具有独立于通过去饱和 - 链延长途径代谢为DHA的潜在作用。
