Division of Gastroenterology, University of Alberta, Edmonton, Alberta, Canada.
Good Nutrition for Good Living, Dallas, Texas, USA.
JPEN J Parenter Enteral Nutr. 2019 Aug;43(6):697-707. doi: 10.1002/jpen.1537. Epub 2019 Mar 25.
Linoleic acid (LA) and α-linolenic acid (ALA) must be supplied to the human body and are therefore considered essential fatty acids. This narrative review discusses the signs, symptoms, diagnosis, prevention, and treatment of essential fatty acid deficiency (EFAD). EFAD may occur in patients with conditions that severely limit the intake, digestion, absorption, and/or metabolism of fat. EFAD may be prevented in patients requiring parenteral nutrition by inclusion of an intravenous lipid emulsion (ILE) as a source of LA and ALA. Early ILEs consisted solely of soybean oil (SO), a good source of LA and ALA, but being rich in LA may promote the production of proinflammatory fatty acids. Subsequent ILE formulations replaced part of the SO with other fat sources to decrease the amount of proinflammatory fatty acids. Although rare, EFAD is diagnosed by an elevated triene:tetraene (T:T) ratio, which reflects increased metabolism of oleic acid to Mead acid in the absence of adequate LA and ALA. Assays for measuring fatty acids have improved over the years, and therefore it is necessary to take into account the particular assay used and its reference range when determining if the T:T ratio indicates EFAD. In patients with a high degree of suspicion for EFAD, obtaining a fatty acid profile may provide additional useful information for making a diagnosis of EFAD. In patients receiving an ILE, the T:T ratio and fatty acid profile should be interpreted in light of the fatty acid composition of the ILE to ensure accurate diagnosis of EFAD.
亚油酸（LA）和α-亚麻酸（ALA）必须供给人体，因此被认为是必需脂肪酸。本文综述讨论了必需脂肪酸缺乏症（EFAD）的体征、症状、诊断、预防和治疗。EFAD 可能发生在严重限制脂肪摄入、消化、吸收和/或代谢的患者中。通过将静脉内脂肪乳剂（ILE）作为 LA 和 ALA 的来源，可预防需要肠外营养的患者发生 EFAD。早期的 ILE 仅由富含 LA 和 ALA 的大豆油（SO）组成，但 SO 富含 LA，可能会促进促炎脂肪酸的产生。随后的 ILE 配方用其他脂肪来源替代部分 SO，以减少促炎脂肪酸的量。尽管罕见，但 EFAD 通过升高三烯：四烯（T：T）比值来诊断，这反映了在缺乏足够的 LA 和 ALA 的情况下，油酸向 Mead 酸代谢的增加。随着时间的推移，脂肪酸检测方法得到了改进，因此在确定 T：T 比值是否表明 EFAD 时，必须考虑到所用特定检测方法及其参考范围。对于 EFAD 高度可疑的患者，获得脂肪酸谱可能会为 EFAD 的诊断提供更多有用信息。在接受 ILE 的患者中，应根据 ILE 的脂肪酸组成来解释 T：T 比值和脂肪酸谱，以确保 EFAD 的准确诊断。
