Genomics of lactation: role of nutrigenomics and nutrigenetics in the fatty acid composition of human milk

Milk-Derived Extracellular Vesicles: A Novel Perspective on Comparative Therapeutics and Targeted Nanocarrier Application

Milk-derived extracellular vesicles (mEVs) are emerging as promising therapeutic candidates due to their unique properties and versatile functions. These vesicles play a crucial role in immunomodulation by influencing macrophage differentiation and cytokine production, potentially aiding in the treatment of conditions such as bone loss, fibrosis, and cancer. mEVs also have the capacity to modulate gut microbiota composition, which may alleviate the symptoms of inflammatory bowel diseases and promote intestinal barrier integrity. Their potential as drug delivery vehicles is significant, enhancing the stability, solubility, and bioavailability of anticancer agents while supporting wound healing and reducing inflammation. Additionally, bovine mEVs exhibit anti-aging properties and protect skin cells from UV damage. As vaccine platforms, mEVs offer advantages including biocompatibility, antigen protection, and the ability to elicit robust immune responses through targeted delivery to specific immune cells. Despite these promising applications, challenges persist, including their complex roles in cancer, effective antigen loading, regulatory hurdles, and the need for standardized production methods. Achieving high targeting specificity and understanding the long-term effects of mEV-based therapies are essential for clinical translation. Ongoing research aims to optimize mEV production methods, enhance targeting capabilities, and conduct rigorous preclinical and clinical studies. By addressing these challenges, mEVs hold the potential to revolutionize vaccine development and targeted drug delivery, ultimately improving therapeutic outcomes across various medical fields.

Short-term dietary changes are reflected in the cerebral content of adult ring-billed gulls

Omega-3 long-chain polyunsaturated fatty acids (n3-LCPUFAs) are produced primarily in aquatic ecosystems and are considered essential nutrients for predators given their structural role in vertebrates' cerebral tissues. Alarmingly, with urbanization, many aquatic animals now rely on anthropogenic foods lacking n3-LCPUFAs. In this study undertaken in Newfoundland (Canada), we tested whether recent or longer term diet explains the cerebral fatty acid composition of ring-billed gulls (Larus delawarensis), a seabird that now thrives in cities. During the breeding season, cerebral levels of n3-LCPUFAs were significantly higher for gulls nesting in a natural habitat and foraging on marine food (mean ± s.d.: 32 ± 1% of total identified fatty acids) than for urban nesters exploiting rubbish (27 ± 1%). Stable isotope analysis of blood and feathers showed that urban and natural nesters shared similar diets in autumn and winter, suggesting that the difference in cerebral n3-LCPUFAs during the breeding season was owing to concomitant and transient differences in diet. We also experimentally manipulated gulls' diets throughout incubation by supplementing them with fish oil rich in n3-LCPUFAs, a caloric control lacking n3-LCPUFAs, or nothing, and found evidence that fish oil increased urban nesters' cerebral n3-LCPUFAs. These complementary analyses provide evidence that the brain of this seabird remains plastic during adulthood and responds to short-term dietary changes.

Maternal diet and human milk composition: an updated systematic review

Context

Exclusive breastfeeding for 6 months after birth provides infants with the best start for life. A review by Bravi et al. summarized the importance of maternal diet as a determinant of human milk composition based on data up to 2015, but evidence on nutrient intake level was limited.

Objective

We updated the review by Bravi et al., critically assessed differences in study designs and sampling methods, and graphically visualized trends and associations.

Data sources

PubMed was systematically searched for articles published between January 2015 and March 2021.

Data extraction

Article screening, selection, and data extraction was done by two independent researchers, including a risk of bias assessment based on 11 criteria. Articles were eligible when including: quantitative information, commonly used effect estimates, healthy mother-infant dyads.

Results

Twenty seven observational and five intervention studies were identified (n = 7,138) and combined with results of Bravi et al. Fatty acids were still the most studied human milk components in relation to maternal diet (n = 17 studies) with maternal fish intake being predominantly positively associated with milk ALA (r = 0.28-0.42), DHA (r = 0.24-0.46), and EPA (r = 0.25-0.28) content. PUFAs from diet were generally positively correlated with their concentrations in milk, while SFA intake was negatively associated with several fatty acids in milk. Studies on associations with maternal diet and milk carbohydrates, proteins, vitamins and minerals were limited in number and varied in methods and results.

Conclusion

This updated review shows that evidence on the association between maternal diet and human milk fatty acids is rapidly increasing, but still diversified in methodology and results. Further studies, preferably intervention studies, assessing diet and milk carbohydrates, proteins, vitamins and minerals are needed to be able draw conclusions on the importance of maternal diet for human milk composition as a whole.

Dietary omega-3 fatty acid deficiency from pre-pregnancy to lactation affects expression of genes involved in hippocampal neurogenesis of the offspring

Maternal n-3 PUFA (omega-3) deficiency can affect brain development in utero and postnatally. Despite the evidence, the impacts of n-3 PUFA deficiency on the expression of neurogenesis genes in the postnatal hippocampus remained elusive. Since postnatal brain development requires PUFAs via breast milk, we examined the fatty acid composition of breast milk and hippocampal expression of neurogenesis genes in n-3 PUFA deficient 21d mice. In addition, the expression of fatty acid desaturases, elongases, free fatty acids signaling receptors, insulin and leptin, and glucose transporters were measured. Among the genes involved in neurogenesis, the expression of brain-specific tenascin-R (TNR) was downregulated to a greater extent (∼31 fold), followed by adenosine A2A receptor (A2AAR), dopamine receptor D2 (DRD2), glial cell line-derived neurotrophic factor (GDNF) expression in the n-3 PUFA deficient hippocampus. Increasing dietary LA to ALA (50:1) elevated the ARA to DHA ratio by ∼8 fold in the n-3 PUFA deficient breast milk, with an overall increase of total n-6/n-3 PUFAs by ∼15:1 (p<0.05) compared to n-3 PUFA sufficient (LA to ALA: 2:1) diet. The n-3 PUFA deficient mice exhibited upregulation of FADS1, FADS2, ELOVL2, ELOVL5, ELOVL6, GPR40, GPR120, LEPR, IGF1 and downregulation of GLUT1, GLUT3, and GLUT4 mRNA expression in hippocampus (p<0.05). Maternal n-3 PUFA deficiency affects the hippocampal expression of key neurogenesis genes in the offspring with concomitant expression of desaturase and elongase genes, suggesting the importance of dietary n-3 PUFA for neurodevelopment.

Breastmilk PUFA strongly associated with maternal dietary intake but not anthropometric parameters and breastmilk carotenoids

BACKGROUND

Long chain polyunsaturated fatty acids (PUFA) and the optimal n-6/n-3 fatty acids ratio are essential for proper neurodevelopment in infancy. This study aimed to evaluate the association between breastmilk fatty acid intake and maternal dietary intake, anthropometrics and breastmilk carotenoid levels.

METHODS

This observational, prospective study included 44 women in the first, third, and sixth month of lactation. At each study visit, maternal anthropometric measures were assessed and breastmilk samples were collected and assessed for fatty acids and carotenoids. At the third and sixth month, maternal diet was evaluated by three-day foods record.

RESULTS

Mean breastmilk docosahexaenoic (DHA) was 0.58%, 0.47%, and 0.49%, respectively at the 1, 3, and 6 month (p ≤ 0.05). Mean DHA intake were higher in month 3 compared to 6: 357 vs. 169 mg/day. Pre-pregnancy BMI was associated with SFA, PUFA, and n-6 PUFA at 1 month, whereas current BMI to SFA at months 1 and 3. DHA was correlated with lycopene, total carotenoids at 1 month and total carotenoids at month 3, whereas n-3 PUFA to lycopene at 1 month. DHA, n-3 PUFA, n-6 PUFA and saturated (SFA) levels were associated with its dietary intake both at months 3 and 6, AA/DHA and LA/ALA ratios only at month 3.

CONCLUSIONS

Maternal intake of PUFA and n-6/n-3 ratios were a good predictor of its breastmilk composition, whereas pre-pregnancy and current BMI, as well as breastmilk carotenoids had a limited influence.

Mammary Leukocyte-Assisted Nanoparticle Transport Enhances Targeted Milk Trace Mineral Delivery

Nanoparticles are applied as versatile platforms for drug/gene delivery in many applications owing to their long-retention and specific targeting properties in living bodies. However, the delivery mechanism and the beneficial effect of nanoparticle-retention in many organisms remain largely uncertain. Here, the transport and metabolism of mineral nanoparticles in mammary gland during lactation are explored. It is shown that maternal intravenous administration of iron oxide nanoparticles (IONPs; diameter: ≈11.0 nm, surface charge: -29.1 mV, surface area: 1.05 m2 g-1 ) provides elevated iron delivery to mammary gland and increased iron secretion into breast milk, which is inaccessible by classical iron-ion transport approaches such as the transferrin receptor-mediated endocytic pathway. Mammary macrophages and neutrophils are found to play dominant roles in uptake and delivery of IONPs through an unconventional leukocyte-assisted iron secretion pathway. This pathway bypasses the tight iron concentration regulation of liver hepcidin-ferroportin axis and mammary epithelial cells to increase milk iron-ion content derived from IONPs. This work provides keen insight into the metabolic pathway of nanoparticles in mammary gland while offering a new scheme of nutrient delivery for neonate metabolism regulation by using nanosized nutrients.

Evolutionary adaptation highlights the interconnection of fatty acids, sunlight, inflammation and epithelial adhesion

Gene variants that influence human biology today reflect thousands of years of evolution. Genetic effects on infant health are a major point of selective pressure, given that childhood survival is essential to evolutionary success. Knowledge of this evolutionary history can have implications for paediatric research. CONCLUSION: An episode of human adaptation to the extremely low ultraviolet radiation environment of the Arctic 20,000 years ago implicates the Ectodysplasin A Receptor (EDAR) and the Fatty Acid Desaturases (FADS) in human lactation and epithelial inflammation.

Association between FADS Gene Expression and Polyunsaturated Fatty Acids in Breast Milk

Polyunsaturated fatty acid (PUFA) in breast milk provides physiological benefits for offspring and is closely related to endogenous biosynthesis in lactating women. Few studies have addressed the association between fatty acid desaturase (FADS) gene expression patterns and fatty acids in breast milk. This research aimed to explore the differences in PUFA levels among breast milk groups with different levels of FADS gene expression and provide a scientific basis for precision nutrition strategies. A total of 50 healthy women 42–45 days postpartum were included in this study. A basic information questionnaire and breast milk samples were collected. Eight types of PUFA were detected, and RNA was extracted from breast milk. The transcription level of the FADS gene was detected using real-time quantitative PCR. Significant differences in the content of gamma-linolenic acid and eicosatrienoic acid (C20:3n6) were found in breast milk among FADS1 gene transcription groups (p = 0.009, p = 0.042, respectively). No significant differences in PUFA were found among the FADS2 and FADS3 gene expression groups. The results demonstrated that n-6 PUFA was associated with the mRNA expression levels of the FADS1 gene. They are of great significance in developing new methods and diets to optimize infant feeding using breast milk.

Odor-active volatile compounds in preterm breastmilk

BACKGROUND

Volatile compounds in breastmilk (BM) likely influence flavor learning and, through the cephalic phase response, metabolism, and digestion. Little is known about the volatile compounds present in preterm BM. We investigated whether maternal or infant characteristics are associated with the profile of volatile compounds in preterm BM.

METHODS

Using solid-phase microextraction coupled with gas chromatography/mass spectrometry, we analyzed volatile compounds in 400 BM samples collected from 170 mothers of preterm infants.

RESULTS

Forty volatile compounds were detected, mostly fatty acids and their esters (FA and FAe), volatile organic compounds (VOCs), aldehydes, terpenoids, alcohols, and ketones. The relative concentration of most FA and FAe increased with advancing lactation and were lower in BM of most socially deprived mothers and those with gestational diabetes (p < 0.05), but medium-chain FAs were higher in colostrum compared to transitional BM (p < 0.001). Infant sex, gestational age, and size at birth were not associated with the profile of volatile compounds in preterm BM.

CONCLUSIONS

Sensory-active volatile FA and FAe are the major contributors to the smell of preterm BM. The associations between lactation stage, maternal characteristics, and volatile compounds, and whether differences in volatile compounds may affect feeding behavior or metabolism, requires further research.

IMPACT

Sensory-active volatile FAs are major contributors to the smell of preterm BM and are influenced by the lactation stage and maternal characteristics. Longitudinal analysis of volatile compounds in preterm BM found that FAs increased with advancing lactation. Colostrum had a higher concentration of medium-chain FAs compared to transitional BM and the concentration of these is associated with socioeconomic status, gestational diabetes, and ethnicity.

Macronutrient content and fatty acid composition and their positional distribution in human breast milk from Zhejiang Province, China in different lactation periods

Lactational changes in macronutrient content, lipid profile, fatty acid composition, and positional distribution of human breast milk were investigated in this study. A total of 378 milk samples of six different lactation periods, including 0‒5, 6‒14, 15‒30, 31‒90, 91‒180, and 181‒360 days, were collected cross-sectionally from healthy lactating women in Zhejiang, China. As lactation progressed from 0‒5 to 15‒30 days, the lipid content and the percentages of C10:0, C12:0, C14:0, C18:2n-6, and C18:3n-3 increased significantly, while the protein concentration and the proportions of phospholipids, cholesterols, C16:0, C18:1n-9, C24:1n-9, C20:4n-6, C22:4n-6, C22:5n-3, and C22:6n-3 decreased notably. When lactation was further extended to 181‒360 days, the protein content continued to decrease, and the percentages of C12:0 and C14:0 continued to increase, whereas the levels of other tested nutrients remained stable. Although the triacylglycerol positional distributions of some fatty acids underwent significant lactational variations, C14:0, C16:0, C24:1n-9, C22:4n-6, C22:5n-3, and C22:6n-3 were located mainly at the sn-2 position, while C18:1n-9, C18:2n-6, and C18:3n-3 were primarily distributed at the sn-1,3 positions. Compared with human breast milk reported in Western countries, samples in our study demonstrated higher percentages of C18:2n-6, C18:3n-3, C20:4n-6, and C22:6n-3, but lower proportions of C12:0, C14:0, and C18:1n-9. The results from this study indicated a nutritional composition different from that of the Western countries and may provide useful data for the development of infant formulas closer to Chinese breast milk in terms of the fatty acid composition and its specified positional distribution on triglyceride structure.

Extracellular Vesicles in Human Milk

Milk supports the growth and development of infants. An increasing number of mostly recent studies have demonstrated that milk contains a hitherto undescribed component called extracellular vesicles (EVs). This presents questions regarding why milk contains EVs and what their function is. Recently, we showed that EVs in human milk expose tissue factor, the protein that triggers coagulation or blood clotting, and that milk-derived EVs promote coagulation. Because bovine milk, which also contains EVs, completely lacks this coagulant activity, important differences are present in the biological functions of human milk-derived EVs between species. In this review, we will summarize the current knowledge regarding the presence and biochemical composition of milk EVs, their function(s) and potential clinical applications such as in probiotics, and the unique problems that milk EVs encounter in vivo, including survival of the gastrointestinal conditions encountered in the newborn. The main focus of this review will be human milk-derived EVs, but when available, we will also include information regarding non-human milk for comparison.

Exosome-Derived MicroRNAs of Human Milk and Their Effects on Infant Health and Development

Multiple biologically active components of human milk support infant growth, health and development. Milk provides a wide spectrum of mammary epithelial cell-derived extracellular vesicles (MEVs) for the infant. Although the whole spectrum of MEVs appears to be of functional importance for the growing infant, the majority of recent studies report on the MEV subfraction of milk exosomes (MEX) and their miRNA cargo, which are in the focus of this review. MEX and the dominant miRNA-148a play a key role in intestinal maturation, barrier function and suppression of nuclear factor-κB (NF-κB) signaling and may thus be helpful for the prevention and treatment of necrotizing enterocolitis. MEX and their miRNAs reach the systemic circulation and may impact epigenetic programming of various organs including the liver, thymus, brain, pancreatic islets, beige, brown and white adipose tissue as well as bones. Translational evidence indicates that MEX and their miRNAs control the expression of global cellular regulators such as DNA methyltransferase 1-which is important for the up-regulation of developmental genes including insulin, insulin-like growth factor-1, α-synuclein and forkhead box P3-and receptor-interacting protein 140, which is important for the regulation of multiple nuclear receptors. MEX-derived miRNA-148a and miRNA-30b may stimulate the expression of uncoupling protein 1, the key inducer of thermogenesis converting white into beige/brown adipose tissue. MEX have to be considered as signalosomes derived from the maternal lactation genome emitted to promote growth, maturation, immunological and metabolic programming of the offspring. Deeper insights into milk's molecular biology allow the conclusion that infants are both "breast-fed" and "breast-programmed". In this regard, MEX miRNA-deficient artificial formula is not an adequate substitute for breastfeeding, the birthright of all mammals.

Perinatal Dietary Polyunsaturated Fatty Acids in Brain Development, Role in Neurodevelopmental Disorders

n-3 and n-6 polyunsaturated fatty acids (PUFAs) are essential fatty acids that are provided by dietary intake. Growing evidence suggests that n-3 and n-6 PUFAs are paramount for brain functions. They constitute crucial elements of cellular membranes, especially in the brain. They are the precursors of several metabolites with different effects on inflammation and neuron outgrowth. Overall, long-chain PUFAs accumulate in the offspring brain during the embryonic and post-natal periods. In this review, we discuss how they accumulate in the developing brain, considering the maternal dietary supply, the polymorphisms of genes involved in their metabolism, and the differences linked to gender. We also report the mechanisms linking their bioavailability in the developing brain, their transfer from the mother to the embryo through the placenta, and their role in brain development. In addition, data on the potential role of altered bioavailability of long-chain n-3 PUFAs in the etiologies of neurodevelopmental diseases, such as autism, attention deficit and hyperactivity disorder, and schizophrenia, are reviewed.

Evolution of breast milk fatty acids in Spanish mothers after one year of uninterrupted lactation

The WHO recommends exclusive breastfeeding of infants for the first sixth months of life and advises that it shall continue for up to two years of age or beyond in combination with complementary foods. However, the image of a woman breastfeeding a toddler or a preschooler is unusual in western societies. Exploring the nutritional properties of milk during prolonged lactation can help normalizing prolonged breastfeeding. Human milk fatty acid composition was determined in sixteen lactating mothers practicing prolonged lactation (≥12 months) and sixteen women on their first twelve months of lactation. Breast milk after one year is richer in saturated fatty acids, particularly lauric and myristic, showing a tendency towards lower levels of oleic acid, and higher of arachidonic, α-linolenic and docosahexaenoic acids, in comparison to early milk (< 1 year). The age and body condition of the mother, parity, sex of the baby, and diet influence also the fattyacidome of milk.

Perinatal exposure to diets with different n-6:n-3 fatty acid ratios affects olfactory tissue fatty acid composition

The olfactory mucosa (OM) and the olfactory bulb (OB) are responsible for the detection and processing of olfactory signals. Like the brain and retina, they contain high levels of n-3 and n-6 polyunsaturated fatty acids (PUFAs), which are essential for the structure and function of neuronal and non-neuronal cells. Since the influence of the maternal diet on olfactory lipid profiles of the offspring has been poorly explored, we examined the effects of feeding mice during the perinatal period with diets containing an adequate linoleic acid level but either deficient in α-linolenic acid (ALA) or supplemented in n-3 long-chain PUFAs on the lipid composition of dams and weaning offspring olfactory tissues. In both the OM and OB, the low n-3 ALA diet led to a marked reduction in n-3 PUFAs with a concomitant increase in n-6 PUFAs, whereas consumption of the high n-3 PUFA diet reduced n-6 PUFAs and increased n-3 PUFAs. Structural analysis showed that the molecular species profiles of the main phospholipid classes of olfactory tissues from weaning pups were markedly affected by the maternal diets. This study demonstrates that the PUFA status of olfactory tissues is sensitive to diet composition from the early stages of development.

Precision Nutrition and Childhood Obesity: A Scoping Review

Environmental exposures such as nutrition during life stages with high developmental plasticity-in particular, the in utero period, infancy, childhood, and puberty-may have long-lasting influences on risk of chronic diseases, including obesity-related conditions that manifest as early as childhood. Yet, specific mechanisms underlying these relationships remain unclear. Here, we consider the study of 'omics mechanisms, including nutrigenomics, epigenetics/epigenomics, and metabolomics, within a life course epidemiological framework to accomplish three objectives. First, we carried out a scoping review of population-based literature with a focus on studies that include 'omics analyses during three sensitive periods during early life: in utero, infancy, and childhood. We elected to conduct a scoping review because the application of multi-'omics and/or precision nutrition in childhood obesity prevention and treatment is relatively recent, and identifying knowledge gaps can expedite future research. Second, concomitant with the literature review, we discuss the relevance and plausibility of biological mechanisms that may underlie early origins of childhood obesity identified by studies to date. Finally, we identify current research limitations and future opportunities for application of multi-'omics in precision nutrition/health practice.

Maternal cinnamon intake during lactation led to visceral obesity and hepatic metabolic dysfunction in the adult male offspring

PURPOSE

Studies with foods, known to promote health benefits in addition to the nutritive value, show that their consumption by pregnant and/or lactating females could induce negative outcomes to the offspring. It is well characterized that cinnamon intake promotes benefits to energy homeostasis. The present study aimed to analyze the effects of the consumption of an aqueous extract of cinnamon by lactating female rats on the endocrine-metabolic outcomes in the adult offspring.

METHODS

Lactating dams (Wistar rats) were supplemented with cinnamon aqueous extract (400 mg/kg body weight/day) for the entire lactating period. The male adult offspring were evaluated at 180 days old (CinLac).

RESULTS

The offspring presented visceral obesity (P = 0.001), hyperleptinemia (P = 0.002), and hyperinsulinemia (P = 0.016). In the liver, CinLac exhibited reduced p-IRβ (P = 0.018) suggesting insulin resistance. However, phosphorylation of IRS1 (P = 0.041) and AKT (P = 0.050) were increased. JAK2 (P = 0.030) and p-STAT3 (P = 0.015) expressions were higher, suggesting that the activation of IRS1/AKT in the CinLac group could have resulted from the increased activation of leptin signaling. Although we observed no changes in the gluconeogenic pathway, the CinLac group exhibited lower hepatic glycogen content (P = 0.005) accompanied by increased p-GSK3β (P = 0.011). In addition, the CinLac group showed increased hepatic triacylglycerol content (P = 0.049) and a mild steatosis (P = 0.001), accompanied by reduced PPARα mRNA expression (P = 0.005).

CONCLUSION

We conclude that maternal intake of aqueous extract of cinnamon induces long-term molecular, metabolic, and hormonal changes in the adult progeny, including visceral obesity, higher lipid accumulation, and lower glycogen content in the liver.

The antioxidant components of milk and their role in processing, ripening, and storage: Functional food

The current rate of population growth is so fast that, to feed this massive population, a 2-fold increase in land is required for the production of quality food. Improved dietary products such as milk and its products with antioxidant properties and functional foods of animal origin have been utilized to prevent chronic diseases. The designer milk contains low fat and less lactose, more protein, modified level of fatty acids, and desired amino acid profiles. The importance of milk and its products is due to the presence of protein, bioactive peptides, conjugated linoleic acid, omega-3 fatty acid, Vitamin D, selenium, and calcium. These constituents are present in milk product, play a key role in the physiological activities in human bodies, and act as anti-inflammatory, anti-tumor, antioxidant, hypocholesterolemic, immune boosting, and antimicrobial activities. Consumer awareness regarding benefits of designer foods such as milk and its products is almost non-existent worldwide and needs to be established to reach the benefits of designer food technologies in the near future. The main objective of this review was to collect data on the antioxidant properties of milk and its constituents which keep milk-derived products safe and preserved.

Consumption of dairy product and its association with total and cause specific mortality - A population-based cohort study and meta-analysis

BACKGROUND

The intake of dairy products has been thought to be associated with an increased risk of coronary heart diseases (CHD) and total mortality due to its relatively high content of saturated fat. However, reports on this association particularly among US adults are conflicting and controversial. Therefore, we used data from the 1999-2010 National Health and Nutrition Examination Surveys (NHANES) study to examine whether consumption of total dairy and dairy subgroups was associated with total and cause specific (CHD, cerebrovascular and cancer) mortality. Further we carried out a systematic review and meta-analysis of prospective studies to check for consistency with the NHANES findings.

METHODS

In the NHANES cohort vital status through December 31, 2011 was ascertained. Cox proportional hazard regression models were used to relate baseline dairy intake with all-cause and cause-specific mortality. For the systematic review PubMed, SCOPUS, Web of Science and Google Scholar databases were searched (up to December 2017). The DerSimonian-Laird method and generic inverse variance methods were used for quantitative data synthesis.

RESULTS

In the NHANES data set of 24,474 participants, 3520 deaths occurred during follow-up. In multivariate adjusted Cox models, total mortality risk was lower when comparing the top (Q4) with the lower (Q1) quartiles of total dairy (hazard ratio [HR] 0.98, 95% confidence interval [CI]: 0.95-0.99) and cheese (HR: 0.92, 95% CI: 0.87-0.97) consumption. Using a similar model, we have found a negative association between total dairy and milk consumption with risk of cerebrovascular mortality (HR: 0.96, 95% CI: 0.94-0.98, HR: 0.93, 95% CI: 0.91-0.96, respectively), while milk consumption was associated with increased CHD mortality (HR: 1.04, 95% CI: 1.02-1.06). The meta-analysis with 636,726 participants indicated a significant inverse association between fermented dairy products and total mortality (RR: 0.97, 95% CI: 0.96-0.99), while milk consumption was associated with higher CHD mortality (RR: 1.04, 95% CI: 1.01-1.05). These findings were robust in sensitivity analyses.

CONCLUSIONS

Among American adults, higher total dairy consumption was associated with lower total and cerebrovascular mortality, while higher milk consumption was associated with higher risk of CHD. These findings do not support dogmatic public health advice to reduce total dairy fat consumption, although the association between milk consumption and CHD mortality requires further study.

Fatty acid positional distribution (sn-2 fatty acids) and phospholipid composition in Chinese breast milk from colostrum to mature stage

This study quantified the fatty acid profile with emphasis on the stereo-specifically numbered (sn) 2 positional distribution in TAG and the composition of main phospholipids at different lactation stages. Colostrum milk (n 70), transitional milk (n 96) and mature milk (n 82) were obtained longitudinally from healthy lactating women in Shanghai. During lactation, total fatty acid content increased, with SFA dominating in fatty acid profile. A high ratio of n-6:n-3 PUFA was observed as 11:1 over lactation due to the abundance of linoleic acid in Chinese human milk. As the main SFA, palmitic acid showed absolute sn-2 selectivity, while oleic acid, linoleic acid and α-linolenic acid, the main unsaturated fatty acids, were primarily esterified at the sn-1 and sn-3 positions. Nervonic acid and C22 PUFA including DHA were more enriched in colostrum with an sn-2 positional preference. A total of three dominant phospholipids (phosphatidylethanolamine (PE), phosphatidylcholine (PC) and sphingomyelin (SM)) were analysed in the collected samples, and each showed a decline in amount over lactation. PC was the dominant compound followed by SM and PE. With prolonged breast-feeding time, percentage of PE in total phospholipids remained constant, but PC decreased, and SM increased. Results from this study indicated a lipid profile different from Western reports and may aid the development of future infant formula more suitable for Chinese babies.

Environmental selection during the last ice age on the mother-to-infant transmission of vitamin D and fatty acids through breast milk

The frequency of the human-specific EDAR V370A isoform is highly elevated in North and East Asian populations. The gene is known to have several pleiotropic effects, among which are sweat gland density and ductal branching in the mammary gland. The former has led some geneticists to argue that the near-fixation of this allele was caused by selection for modulation of thermoregulatory sweating. We provide an alternative hypothesis, that selection instead acted on the allele’s effect of increasing ductal branching in the mammary gland, thereby amplifying the transfer of critical nutrients to infants via mother’s milk. This is likely to have occurred during the Last Glacial Maximum when a human population was genetically isolated in the high-latitude environment of the Beringia.

Because of the ubiquitous adaptability of our material culture, some human populations have occupied extreme environments that intensified selection on existing genomic variation. By 32,000 years ago, people were living in Arctic Beringia, and during the Last Glacial Maximum (LGM; 28,000–18,000 y ago), they likely persisted in the Beringian refugium. Such high latitudes provide only very low levels of UV radiation, and can thereby lead to dangerously low levels of biosynthesized vitamin D. The physiological effects of vitamin D deficiency range from reduced dietary absorption of calcium to a compromised immune system and modified adipose tissue function. The ectodysplasin A receptor (EDAR) gene has a range of pleiotropic effects, including sweat gland density, incisor shoveling, and mammary gland ductal branching. The frequency of the human-specific EDAR V370A allele appears to be uniquely elevated in North and East Asian and New World populations due to a bout of positive selection likely to have occurred circa 20,000 y ago. The dental pleiotropic effects of this allele suggest an even higher occurrence among indigenous people in the Western Hemisphere before European colonization. We hypothesize that selection on EDAR V370A occurred in the Beringian refugium because it increases mammary ductal branching, and thereby may amplify the transfer of critical nutrients in vitamin D-deficient conditions to infants via mothers’ milk. This hypothesized selective context for EDAR V370A was likely intertwined with selection on the fatty acid desaturase (FADS) gene cluster because it is known to modulate lipid profiles transmitted to milk from a vitamin D-rich diet high in omega-3 fatty acids.