Michelle K. McGuire

Characterization of the Diversity and Temporal Stability of Bacterial Communities in Human Milk

Recent investigations have demonstrated that human milk contains a variety of bacterial genera; however, as of yet very little work has been done to characterize the full diversity of these milk bacterial communities and their relative stability over time. To more thoroughly investigate the human milk microbiome, we utilized microbial identification techniques based on pyrosequencing of the 16S ribosomal RNA gene. Specifically, we characterized the bacterial communities present in milk samples collected from 16 women at three time-points over four weeks. Results indicated that milk bacterial communities were generally complex; several genera represented greater than 5% of the relative community abundance, and the community was often, yet not always, stable over time within an individual. These results support the conclusion that human milk, which is recommended as the optimal nutrition source for almost all healthy infants, contains a collection of bacteria more diverse than previously reported. This finding begs the question as to what role this community plays in colonization of the infant gastrointestinal tract and maintaining mammary health.

High-fat dairy product consumption increases Δ9c’ 11t−18∶2 (rumenic acid) and total lipid concentrations of human milk

Conjugated octadecadienoic acids (18∶2’ conjugated linoleic acids) have been shown to be anticarcinogenic and may influence growth and nutrient partitioning. The Δ9c’ 11t−18∶2 isomer (rumenic acid’ RA) is most common in both food sources and human tissues. To determine if maternal diet can influence milk RA concentration’ breastfeeding women (n=16) were enrolled in a 3-wk crossover study. Women initially consumed minimal amounts of food containing RA during week 1’ then were assigned randomly to consume diets rich in high-fat dairy foods (and thus RA) during week 2 or 3. Milk was collected by complete breast expression twice during each experimental week. Current and chronic RA intakes were estimated by 3-d dietary records and food frequency question-naires’ respectively. Estimated chronic RA intakes ranged from 49 to 659 mg/d. Dietary RA intake was greater during the high compared to the low dairy period (291±75 vs. 15±24 mg/d’ respectively; P<0.0001). Milk contained more RA during the high than the low dairy period (13.5±0.1 vs. 8.2±0.4 μmol/g lipid’ respectively; P<0.0001). Milk lipid concentration was influenced by diet’ such that lipid concentration was greater during the high than the low dairy period (46.6±5.0 vs. 38.3±1.6 mg/g milk’ respectively; P<0.05). Additionally’ multiple regression analyses suggested that body mass index was the primary predictor of milk RA and lipid concentrations. In summary’ these data indicate that both lipid and RA concentrations of human milk can be influenced by diet.

Maternal supplementation with CLA decreases milk fat in humans

CLA refers to isomers of octadecadienoic acid with conjugated double bonds. The most abundant form of CLA (rumenic acid (RA): c9,t11-18∶2) is found in milk and beef fat. Further, CLA supplements containing RA and t10,c12−18∶2 are now available. Consumption of commercially produced CLA has been shown to decrease adipose accretion in growing laboratory and production animals and cause milk fat depression in cows. We tested the hypothesis that CLA supplementation would increase milk CLA concentration and decrease milk fat content in humans. Breastfeeding women (n=9) participated in this double-blind, placebo-controlled, crossover study divided into three periods: intervention l (5 d), washout (7 d), and intervention II (5 d). Women were randomized to treatment order. During each intervention period, women consumed 1.5 g of CLA supplement or placebo (olive oil) daily; during the washout period, no supplements were consumed. Milk was collected by complete breast expression on the final day of each period; milk output was estimated by 24-h weighing on the penultimate day of each intervention period. Milk RA and t10,c12−18∶2 concentrations were greater (P<0.05) during the CLA treatment period as compared to the placebo period. Milk fat content was significantly lower during the CLA treatment, as compared to the placebo treatment (P<0.05). Data indicate no effect of treatment on milk output. Therefore, it would be prudent that lactating women not consume commercially available CLA supplements at this time.

Conjugated linoleic acid concentrations of human milk and infant formula

Conjugated linoleic acid (CLA) is an anticarcinogen found in ruminant products. CLA may also act as a growth promotor in the neonate. Because of the potential importance of CLA to maternal and infant health, CLA concentration was quantified in human milk and infant formula. Human milk samples (n = 14) were collected by complete breast expression, and four brands of formula were analyzed; both powder and ready-to-feed products were studied. Although CLA was detected in only 31% of the formula samples, it was detectable in all human milk. Concentration of the biologically important isoform (c9,t11) of CLA in human milk ranged from 2.23 to 5.43 mg/g fat; that of formula from undetectable to 2.04 mg/g fat. Percent total CLA present as c9,t11 ranged from 83 to 100% in human milk and 80 to 100% in formula. Overall, human milk contained significantly more (P < 0.0001) CLA than did the samples of infant formula containing measurable concentrations (3.64 ± 0.93 vs. 1.35 ± 0.81 mg/g fat, respectively).

Human Milk Oligosaccharides Promote the Growth of Staphylococci

ABSTRACT Human milk oligosaccharides (HMO), which constitute a major component of human milk, promote the growth of particular bacterial species in the infants gastrointestinal tract. We hypothesized that HMO also interact with the bacterial communities present in human milk. To test this hypothesis, two experiments were conducted. First, milk samples were collected from healthy women (n = 16); culture-independent analysis of the bacterial communities was performed, HMO content was analyzed, and the relation between these factors was investigated. A positive correlation was observed between the relative abundance of Staphylococcus and total HMO content (r = 0.66). In a follow-up study, we conducted a series of in vitro growth curve experiments utilizing Staphylococcus aureus or Staphylococcus epidermidis and HMO isolated from human milk. HMO exhibited stimulatory effects on bacterial growth under various nutritional conditions. Analysis of culture supernatants from these experiments revealed that HMO did not measurably disappear from the culture medium, indicating that the growth-enhancing effects were not a result of bacterial metabolism of the HMO. Instead, stimulation of growth caused greater utilization of amino acids in minimal medium. Collectively, the data provide evidence that HMO may promote the growth of Staphylococcus species in the lactating mammary gland.

Use of Nonvitamin, Nonmineral Dietary Supplements Among College Students

Abstract The authors assessed the use of nonvitamin, nonmineral (NVNM) dietary supplements in a college population. They found that the use of NVNM dietary supplements among college students might be higher than that of other population groups and that the types of NVNM products they use differ from those used by an older population. Of the 272 students who completed the questionnaire, 48.5% reported they took an NVNM supplement during the past 12 months. The most frequently used NVNM products were echinacea, ginseng, and St Johns wort. Of the 27 students who took NVNM products to promote weight loss. 81.5% had body mass index (BMI) values in the acceptable range. Eleven of the 19 participants who reported an adverse reaction to an NVNM supplement continued to take the products despite negative effects. Users and nonusers of NVNM supplements did not differ significantly by age, ethnicity, gender, perceived dietary adequacy, or by exercise patterns.

Mastitis is associated with increased free fatty acids, somatic cell count, and interleukin-8 concentrations in human milk.

BACKGROUND Research in bovine lactation has demonstrated that milk produced by a mammary gland displaying inflammation-based symptoms of mastitis has increased levels of free fatty acids (FFAs) compared with milk produced by a contralateral asymptomatic gland. However, the effects of mastitis on lipid classes in milk have not been investigated in humans. METHODS The study described here compared milk collected from the symptomatic breast of women with mastitis (n=14) with that collected from the contralateral asymptomatic breast to determine if mastitis caused alterations in the quantity of total lipids, FFAs, and phospholipids (PLs), as well as the fatty acid profiles of these lipid classes. To assess their efficacy as biomarkers of mastitis, samples were also analyzed for selected markers of local inflammation: sodium, somatic cell count (SCC), and interleukin-8 (IL-8). RESULTS FFAs were higher in milk from the mastitic breast compared with that from the healthy breast (1.31 vs. 1.07 ± 0.10 g/100 g of lipid, p<0.05). Similarly, SCC and IL-8 were elevated roughly 10-fold in milk from mastitic breasts, compared with milk from healthy breasts, and sodium tended to be higher in milk from mastitic breasts (p<0.10). However, there were no differences in total lipid, PLs, or fatty acid profiles within each lipid class. CONCLUSIONS In summary, mastitis is associated with increased lipolysis in the human breast but not alterations in milk fat synthesis, as evidenced by a lack of alteration in total milk lipids. Additionally, these results indicate that SCC and IL-8 may be better indicators of mammary inflammation than sodium content.

What’s normal? Oligosaccharide concentrations and profiles in milk produced by healthy women vary geographically

Background: Human milk is a complex fluid comprised of myriad substances, with one of the most abundant substances being a group of complex carbohydrates referred to as human milk oligosaccharides (HMOs). There has been some evidence that HMO profiles differ in populations, but few studies have rigorously explored this variability. Objectives: We tested the hypothesis that HMO profiles differ in diverse populations of healthy women. Next, we examined relations between HMO and maternal anthropometric and reproductive indexes and indirectly examined whether differences were likely related to genetic or environmental variations. Design: In this cross-sectional, observational study, milk was collected from a total of 410 healthy, breastfeeding women in 11 international cohorts and analyzed for HMOs by using high-performance liquid chromatography. Results: There was an effect of the cohort (P < 0.05) on concentrations of almost all HMOs. For instance, the mean 3-fucosyllactose concentration was >4 times higher in milk collected in Sweden than in milk collected in rural Gambia (mean ± SEM: 473 ± 55 compared with 103 ± 16 nmol/mL, respectively; P < 0.05), and disialyllacto-N-tetraose (DSLNT) concentrations ranged from 216 ± 14 nmol/mL (in Sweden) to 870 ± 68 nmol/mL (in rural Gambia) (P < 0.05). Maternal age, time postpartum, weight, and body mass index were all correlated with several HMOs, and multiple differences in HMOs [e.g., lacto-N-neotetrose and DSLNT] were shown between ethnically similar (and likely genetically similar) populations who were living in different locations, which suggests that the environment may play a role in regulating the synthesis of HMOs. Conclusions: The results of this study support our hypothesis that normal HMO concentrations and profiles vary geographically, even in healthy women. Targeted genomic analyses are required to determine whether these differences are due at least in part to genetic variation. A careful examination of sociocultural, behavioral, and environmental factors is needed to determine their roles in this regard. This study was registered at clinicaltrials.gov as NCT02670278.

Documentation of Fatty Acid Profiles in Lamb Meat and Lamb‐Based Infant Foods

UNLABELLED Lamb meat, when used in the weaning diet of children, is presumed to have a lower allergenicity than other forms of red meat. In children with atopic dermatitis and multiple food hypersensitivities, consumption of lamb meat has also resulted in significant clinical improvements in the severity of the eczematous lesions. Lamb meat is also of special interest in infant nutrition because it provides a somewhat unique fatty acid (FA) profile that mirrors what is thought to be optimal for neonatal growth and development. However, very little is known about how the processing of fresh meat (FM) into prepared infant foods influences its FA composition. In this study, we compared the FA profile of FM from suckling lambs with those of homogenized (HO) and lyophilized (LIO) baby foods prepared primarily with lamb meat. The results show that the content of total omega-3 polyunsaturated FAs was the highest in FM (more than 3-fold) compared to commercial baby food, due to largely higher contents of α-linolenic acid (1.5-fold higher), eicosapentaenoic acid (6-fold higher), and docosahexaenoic acid (10-fold higher). Furthermore, arachidonic acid was more than 6-fold higher in FM compared to LIO and HO. Results from this study suggest the possibility of enhancing the FA profile of commercial baby food based on meat by using lamb meat, but care should be taken during processing so that important FAs are not lost. PRACTICAL APPLICATION In this article, we have documented that meat from the suckling lamb is an interesting and potentially important source of omega-3-FAs, especially some of the long-chain polyunsaturated FAs (LC-PUFAs) that are essential for optimal neonatal growth and development. These results may have special implications to the infant food industry, in that products made using meat from suckling lambs may provide not only exceptional amounts of these FAs, but also other limiting essential nutrients such as iron. This may be especially important in regions of the world, such as Italy, where use of lamb meat as a weaning food is common during infancy.

Food restriction, gonadotropins, and behavior in the lactating rat

This study sought to quantify effects of undernutrition on behaviors and to relate these to gonadotropin and prolactin concentrations in the lactating dam. Dams were studied in a 2 x 3 factorial design with litter size and food intake as the two factors. Behavioral data were collected from each dam and her litter on day 9, day 14, and day 19 of lactation, and maternal blood samples collected. Plasma was analyzed for luteinizing hormone, follicle stimulating hormone and prolactin. On day 15 of lactation, percent time nursing, number of pups actively nursing, total number of pups nursing and dam location acted as mediating factors of the effect of diet group on plasma luteinizing hormone concentration. No such relationships were seen for plasma follicle stimulating hormone, and only nest condition score appeared to be a mediator for plasma prolactin concentration. In conclusion, this analysis suggests that food restriction indirectly influences plasma concentration of luteinizing hormone, but not follicle stimulating hormone, by changing maternal and pup behaviors. The relationship among diet, behavior and circulating prolactin was less clear.