Milk at altitude: Human milk macronutrient composition in a high‐altitude adapted population of tibetans

Objectives Dental eruption schedules have been closely linked to life history variables. Here we examine a sample of 50 perinatal primates (28 species) to determine whether life history traits correlate with relative tooth size at birth. Materials and Methods Newborn primates were studied using serial histological sectioning. Volumes of deciduous premolars (dp2-dp4), replacement teeth (if any), and permanent molars (M1−2/3) of the upper jaw were measured and residuals from cranial length were calculated with least squares regressions to obtain relative dental volumes. Results Relative dental volumes (RDVs) of deciduous or permanent teeth have an unclear relationship with relative neonatal mass in all primates. Relative palatal length (RPL), used as a proxy for midfacial size, is significantly, positively correlated with larger deciduous and permanent postcanine teeth. However, when strepsirrhines alone are examined, larger RPL is correlated with smaller RDV of permanent teeth. In the full sample, RDVs of deciduous premolars are significantly negatively correlated with relative gestation length (RGL), but have no clear relationship with relative weaning age. RDVs of molars lack a clear relationship with RGL; later weaning is associated with larger molar RDV, although correlations are not significant. When strepsirrhines alone are analyzed, clearer trends are present: longer gestations or later weaning are associated with smaller deciduous and larger permanent postcanine teeth (only gestational length correlations are significant). Discussion Our results indicate a broad trend that primates with the shortest RGLs precociously develop deciduous teeth; in strepsirrhines, the opposite trend is seen for permanent molars. Anthropoids delay growth of permanent teeth, while strepsirrhines with short RGLs are growing replacement teeth concurrently. A comparison of neonatal volumes with existing information on extent of cusp mineralization indicates that growth of tooth germs and cusp mineralization may be selected for independently.

Section: Discussionmentioning

confidence: 94%

Relative tooth size at birth in primates: Life history correlates

Smith

Muchlinski

Bucher

et al. 2017

“…The maternal buffering hypothesis (Pond, ; a thorough review in Quinn, Diki Bista, & Childs ()), suggests that nutrients in mammalian milk may be buffered against impairments because of moderate environmental stress and maternal nutrition primarily mediated by maternal body fat store. We apply this hypothesis to the question of maternal anemia: instead of maternal energy balance per se , we utilize a broad concept of maternal functional nutrition/health––consisting of the complex interplay of macronutrient stores, micronutrient stores, and other health conditions (e.g., presence of infections) that can cause anemia when jeopardized––as the foundational resource that enables mothers to buffer milk nutrients.…”

Section: Introductionmentioning

confidence: 99%

Buffered or impaired: Maternal anemia, inflammation and breast milk macronutrients in northern Kenya

Fujita

Ruvalcaba

Wander

et al. 2018

Background: Maternal anemia has adverse consequences for the mother-infant dyad. To evaluate whether and how milk nutrient content may change in ways that could "buffer" infants against the conditions underlying maternal anemia, this study assessed associations between milk macronutrients and maternal iron-deficiency anemia (IDA), non-iron-deficiency anemia (NIDA), and inflammation.Methods: A secondary analysis of cross-sectional data and milk from northern Kenya was conducted (n = 204). The combination of hemoglobin and transferrin receptor defined IDA/NIDA. Elevated serum C-reactive protein defined acute inflammation. The effects of IDA, NIDA, and inflammation on milk macronutrients were evaluated in regression models.Results: IDA (β = 0.077, p = .022) and NIDA (β = 0.083, p = .100) predicted higher total protein (ln). IDA (β = −0.293, p = .002), NIDA (β = −0.313, p = .047), and inflammation (β = −0.269, p = .007) each predicted lower fat (ln); however, anemia accompanying inflammation predicted higher fat (β = 0.655, p = .007 for IDA and β = 0.468, p = .092 for NIDA). NIDA predicted higher lactose (β = 1.020, p = .003).Conclusions: Milk macronutrient content both increases and decreases in the presence of maternal anemia and inflammation, suggesting a more complicated and dynamic change than simple impairment of nutrient delivery during maternal stress. Maternal fat delivery to milk may be impaired under anemia. Mothers may buffer infant nutrition against adverse conditions or poor maternal health by elevating milk protein (mothers with IDA/NIDA), lactose (mothers with NIDA), or fat (mothers with anemia and inflammation). This study demonstrates the foundational importance of maternal micronutrient health and inflammation or infection for advancing the ecological understanding of human milk nutrient variation.

“…Females mobilize somatic resources to support offspring growth and biobehavioral development for extended periods among primates (Hinde and Capitanio, 2010; Hinde et al 2015). Body condition (human: Dewey et al, 1994; Quinn et al, 2016; rhesus macaque: Hinde, 2007a; baboon: Roberts et al, 1985; marmoset: Tardif et al, 2001), parasite load (rhesus macaque: Hinde, 2007a), and nutritional intake (baboon: Roberts et al, 1985) have all been implicated in the capacity to synthesize milk in terms of quantity (volume/yield), quality (energetic density), or both (Hinde and Milligan 2011). Primparous mothers produce lower yields of milk than do multiparous mothers (Doreau et al, 1991; Miller et al, 2006), even controlling for body size (Hinde et al, 2009).…”

mentioning

confidence: 99%

Age at reproductive debut: Developmental predictors and consequences for lactation, infant mass, and subsequent reproduction in rhesus macaques (Macaca mulatta)

Pittet

Johnson

Hinde

2017

Objectives The age at which females initiate their reproductive career is a critical life-history parameter with potential consequences on their residual reproductive value and lifetime fitness. The age at reproductive debut may be intimately tied to the somatic capacity of the mother to rear her young, but relatively little is known about the influence of age of first birth on milk synthesis within a broader framework of reproductive scheduling, infant outcomes, and other life-history tradeoffs. Material and Methods Our study investigated the predictors of age at first reproduction among 108 captive rhesus macaque (Macaca mulatta) females, and associations with their milk synthesis at peak lactation, infant mass and ability to subsequently conceive and reproduce. Results The majority of females reproduced in their fourth year (typical breeders); far fewer initiated their reproductive career one year earlier or one year later (respectively early and late breeders). Early breeders (3-year-old) benefited from highly favorable early life development (better juvenile growth, high dominance rank) to accelerate reproduction, but were impaired in milk synthesis due to lower somatic resources and their own continued growth. Comparatively, late breeders suffered from poor developmental conditions, only partially compensated by their delayed reproduction, and evinced compromised milk synthesis. Typical breeders not only produced higher available milk energy but also had best reproductive performance during the breeding and birth seasons following primiparity. Discussion Here we refine and extend our understanding of how life-history tradeoffs manifest in the magnitude, sources, and consequences of variation in age of reproductive debut. These findings provide insight into primate reproductive flexibility in light of constraints and opportunities.