The Influence Of Dietary Oils On Polyunsaturated Fatty Acids Composition In Human Milk

Polyunsaturated fatty acids(PUFA)are of great interest for their regulation of dynamic homeostasis and their role in brain signaling,neural and visual systems.The content of PUFA in human milk may be influenced by factors such as lactation stage,region and maternal diet.It is crucial to continuously dissect the composition and distribution of PUFA and clarify its relationship with influencing factors so as to optimize the quality of human milk in terms of meeting the dietary nutritional requirements of infants from 0 to 6 months of age.Therefore,this study firstly summarized the nutrients in human milk that are susceptible to dietary influences,compared the content of PUFA in Chinese human milk with the dietary nutritional requirements of infants.And then we determined the fat composition of 300 human milk samples,and analyzed the role of lactation stage and region to further investigate the influence of the type of dietary oils of mothers on the fat composition of human milk.The main research contents are as follows:Firstly,the effects of maternal diet on the nutrient content of human milk were systematically summarized through a literature review.The results showed that the human milk nutrients that were susceptible to dietary influences included: PUFA including linoleic acid(L),linolenic acid(Ln)and docosahexaenoic acid(DHA);trans fatty acids including isoleic acid and ruminal acid;fat-soluble vitamin A,water-soluble vitamins including vitamin C,vitamin B1 and vitamin B2;and trace minerals including zinc,iron and selenium.Human milk nutrients that are not susceptible to dietary influences include: total protein,total carbohydrate,and macrominerals including calcium,magnesium,and potassium.The influences of maternal diet on total fat content,saturated fatty acids,monounsaturated fatty acids,and vitamin E in human milk are not known.Secondly,the characteristics of PUFA composition of Chinese human milk were systematically compared with the dietary nutritional requirements of infants.The results showed that compared with the reference intakes of infants from 0 to 6 months of age,Chinese human milk had higher L content,relatively stable ARA content,lower Ln and DHA content with a wide fluctuation range,and higher L/Ln ratio,and PUFA had a tendency to decrease in content with lactation.Further analysis of regional factors revealed that the regions with L/Ln ratio greater than 20 were mainly concentrated in soybean processing such as northeast and coastal regions and peanut processing industrial areas such as Shandong and Hebei,indicating that maternal dietary oils may affect the content of PUFA in human milk.Thirdly,the composition characteristics of PUFA,sn-2 PUFA and polyunsaturated fatty acids-triacylglycerol(PUFA-TAG)in 300 human milk samples from five regions and three lactation stages in China were analyzed.The results showed that 33 fatty acids and 31 sn-2 fatty acids were detected by gas chromatography,and 129 kinds of triacylglycerol were detected by ultra-performance liquid chromatography-triple quadrupole-time-of-flight mass spectrometry(UPLC-Q-TOF-MS),in which the contents of PUFA,sn-2 PUFA and PUFA-TAG ranged from23.64% to 27.43%,11.60% to 18.12% and 61.53%～66.24%,respectively.Both lactation stage and region had an effect on PUFA,with a significant effect on n-3 PUFA(P<0.001).The content of PUFA-TAG in human milk was more stable during lactation and varied significantly between regions,with the content of L-TAG and L/Ln-TAG affected by region only,while the content of Ln-TAG and L+Ln-TAG were affected by both lactation and region(P<0.05).Finally,the effect of the type of maternal dietary oils on PUFA,sn-2 PUFA and PUFATAG in human milk was analyzed.Grouped according to the type of dietary oils and their fatty acids content in the 24-hour dietary review,the results showed that the content of n-6 PUFA in human milk was positively correlated with the content of L and PUFA in dietary oils.The content of n-3 PUFA was positively correlated with the content of Ln in dietary oils.The contents of PUFA-TAG,L-TAG and L/Ln-TAG in human milk were positively correlated with L content(P<0.05)and negatively correlated with Ln content in dietary oils.The content and ratio of ARA and DHA in human milk were not significantly different between human milk of different types of dietary oils.The content of L,ARA and n-6 PUFA at sn-2 position in human milk were not affected by the type of dietary oils,while the content of sn-2 Ln and sn-2 n-3PUFA were higher in the high Ln group.The content of Ln-TAG and L+Ln-TAG was higher in human milk consuming soybean oil and corn oil than consuming peanut oil(P<0.05).This suggests that n-6 PUFA and n-3 PUFA in milk are influenced by the maternal dietary oils.In summary,this thesis analyzed the nutrients in human milk that are influenced by maternal diet,clarified the relationship between the content of PUFA in human milk and infant reference intakes,and its effect of lactation stage and region on PUFA in human milk,and found that maternal dietary oils affect the content of PUFA in human milk.This thesis provided data to support nutritional strategies to adjust the content and ratio of PUFA by adjusting maternal dietary oils and to improve the quality of breastfeeding.