Brenna J Thomas, Salem Norman, Sinclair Andrew J, Cunnane Stephen C
Division of Nutritional Sciences, Cornell University, Savage Hall, Ithaca, NY 14853, USA.
Prostaglandins Leukot Essent Fatty Acids. 2009 Feb-Mar;80(2-3):85-91. doi: 10.1016/j.plefa.2009.01.004. Epub 2009 Mar 9.
Blood levels of polyunsaturated fatty acids (PUFA) are considered biomarkers of status. Alpha-linolenic acid, ALA, the plant omega-3, is the dietary precursor for the long-chain omega-3 PUFA eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). Studies in normal healthy adults consuming western diets, which are rich in linoleic acid (LA), show that supplemental ALA raises EPA and DPA status in the blood and in breast milk. However, ALA or EPA dietary supplements have little effect on blood or breast milk DHA levels, whereas consumption of preformed DHA is effective in raising blood DHA levels. Addition of ALA to the diets of formula-fed infants does raise DHA, but no level of ALA tested raises DHA to levels achievable with preformed DHA at intakes similar to typical human milk DHA supply. The DHA status of infants and adults consuming preformed DHA in their diets is, on average, greater than that of people who do not consume DHA. With no other changes in diet, improvement of blood DHA status can be achieved with dietary supplements of preformed DHA, but not with supplementation of ALA, EPA, or other precursors.
多不饱和脂肪酸（PUFA）的血液水平被视为状态的生物标志物。α-亚麻酸（ALA），即植物性ω-3脂肪酸，是长链ω-3多不饱和脂肪酸二十碳五烯酸（EPA）、二十二碳五烯酸（DPA）和二十二碳六烯酸（DHA）的膳食前体。对食用富含亚油酸（LA）的西方饮食的正常健康成年人进行的研究表明，补充ALA可提高血液和母乳中EPA和DPA的水平。然而，ALA或EPA膳食补充剂对血液或母乳中的DHA水平影响很小，而食用预先形成的DHA则能有效提高血液中的DHA水平。在配方奶喂养婴儿的饮食中添加ALA确实会提高DHA水平，但所测试的任何ALA水平都无法将DHA提高到与典型人乳DHA供应量相似的摄入量下预先形成的DHA所能达到的水平。饮食中食用预先形成的DHA的婴儿和成年人的DHA状态平均高于不食用DHA的人。在饮食无其他变化的情况下，通过预先形成的DHA膳食补充剂可改善血液中的DHA状态，但补充ALA、EPA或其他前体则无法实现。
