Both linoleic acid (18:2 n-6, LA) and α-linolenic acid (18:3 n-3, ALA) are essential fatty acids for infants. The contents of LA and ALA, and their ratio exhibited significant changes in human milk over the past 4 decades, which were not well summarized. Here, we summarized these values in 9898 human breast milk samples of 6664 mothers from 50 countries in 81 studies. A literature search was conducted using PubMed, Embase, and Web of Science between January 1980 and October 2023. The 95% confidence interval of LA/ALA ratio across lactation and gestation ranged from 14.24 to 31.26. The LA content was higher in China and Turkey (> 20%) whereas the ALA content was below 1% in Africa. The LA/ALA ratio in countries along the Mediterranean coast exceeded 20 or even 30. LA and ALA contents increased significantly (P < 0.01) while the ratio remained stable over the last 40 years. Multivariate meta-regression results showed that regions significantly (P < 0.01) determined the LA, ALA, and LA/ALA ratio. Especially, maternal diet could definitely explain the variation while the effects of gestational age, lactation period was not significant. Clinical trials demonstrated that decreasing the LA/ALA ratio increased docosahexaenoic acid (22:6 n-3, DHA) status, reduced arachidonic acid (20:4 n-6, AA) contents, exerted no effect on the visual function of infants, and reached no consensus on growth. The current review aims to provide an overview on the LA and ALA contents and their ratio in human breast milk to raise concern in infant formula.

Background & Aims: Previous studies have established a significant association between dietary fatty acid intake and cardiovascular disease (CVD) risk; however, the long-term effects in China, where CVD rates are high, remain unclear. This study aims to assess the associations between long-term dietary fatty acid intake and CVD risk in Chinese populations. Methods: A total of 8,456 participants from the China Health and Nutrition Survey (CHNS) were enrolled. Dietary fatty acid intake was assessed using three-day 24-h dietary recalls combined with the dietary weighing method. CVD was defined as adults with myocardial infarction (MI) and/or stroke. Multivariable Cox proportional hazards models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs), while restricted cubic spline (RCS) curves assessed the non-linear association. Results: During a median follow-up of 7 years, 418 participants developed CVD (186 MI and 251 stroke cases, including 19 with both conditions). In Chinese adults, more polyunsaturated fatty acids (PUFA) and n-6 PUFA intake was associated with an increased risk of CVD. Specifically, higher linoleic acid (C18:2n-6) intake was associated with a higher risk of CVD (HR_Q4vsQ1=1.80, 95% CI: 1.32-2.45), MI (HR_Q4vsQ1= 1.68, 95% CI: 1.06-2.68), and stroke (HR_Q4vsQ1=1.78, 95% CI: 1.22-2.60). Similar associations were observed between α-linolenic acid (C18:3n-3) and CVD (HR_Q4vsQ1=1.88, 95% CI: 1.38-2.57) and MI risk (HR_Q4vsQ1=3.84, 95% CI: 2.17-6.78), but no significant association was found for stroke. Furthermore, higher saturated fatty acid (SFA) intake was associated with an increased MI risk (HR_Q4vsQ1=1.64, 95% CI: 1.03-2.65). In contrast, the intake of marine n-3 PUFA, mainly composed of eicosapentaenoic acid and docosahexaenoic acid, was inversely linked to MI risk (HR_Q4vsQ1=0.51, 95% CI: 0.33-0.80). No significant correlation was detected between dietary monounsaturated fatty acid and cardiovascular event risk in Chinese adults. Similar findings for these fatty acids were also observed in RCS analyses. Conclusion: Higher dietary intake of marine n-3 PUFA was associated with a lower MI risk, while intakes of n-6 PUFA, C18:2n-6, and SFA were linked to a higher CVD risk. These findings support limiting the intake of n-6 PUFA and SFA while increasing marine n-3 PUFA consumption in the Chinese population for CVD prevention, particularly MI.

Nutrients in human milk are influenced by maternal diet, but it is still clear which type(s) of nutrients can be attributed to dietary changes. Most studies do not directly assess maternal diet or quantify the relationship between maternal diet and human milk composition. In this study, we retrieved and analyzed 24 observational studies, 5 crossover experimental studies and 11 parallel controlled experimental studies concerning ‘human milk/breast milk’, ‘nutrient’, ‘macronutrient’, ‘micronutrient’, ‘maternal nutrition’ and ‘maternal diet’ from the literature published before May 2022 in the PubMed and the Web of Science databases. It was found that in the diet of lactating mothers, fatty acids, especially polyunsaturated and trans fatty acids, and certain micronutrients, including fat-soluble vitamins (vitamins A and D), water-soluble vitamins (vitamin C) and trace minerals (iron, zinc and selenium), were closely related to their contents in human milk.