OBJECTIVES:Betel quid is used as a mild stimulant in many parts of South and East Asia and the Pacific. In observational studies, its use has been associated with elevated risk for diabetes, but studies in animal models suggest some component(s) of betel quid could reduce risk. METHODS:We assessed associations between betel quid use and diabetes (glycated hemoglobin, HbA1c ≥ 6.5%) among a cross-sectional sample of 410 men and 717 non-pregnant women in Matlab, Bangladesh. RESULTS:In multivariable logistic regression, betel quid use was inversely associated with diabetes among men (aOR: 0.45; 95% CI: 0.26, 0.79) but not women (aOR: 0.88; 95% CI: 0.51, 1.52). There was a dose-response relationship between frequency of betel quid use and diabetes among men (aOR: 0.73; 95% CI: 0.59, 0.89), but not women (aOR: 0.96; 95% CI: 0.77, 1.18). Betel quid use was inversely associated with diabetes as an ordinal variable (no diabetes/prediabetes/diabetes) among men (aOR: 0.55; 95% CI: 0.36, 0.82) and women (aOR: 0.66; 95% CI: 0.47, 0.94). Structural equation modeling suggested that some of the inverse association was mediated by food source (market vs. household production). CONCLUSIONS:These models support the hypothesis that betel quid use could decrease, rather than increase, risk for diabetes in the Bangladeshi context, particularly among men (who have more frequent betel quid use than women). Heterogeneity in betel quid preparation across settings, multifactorial effects of betel quid use, and publication bias may contribute to differences between these findings and other observational studies.

OBJECTIVES:Adverse environmental conditions during early life can increase the risk of obesity in adulthood, but the underlying mechanisms are not completely understood. Here, we test the hypothesis that early-life adversity leads to a lower metabolic rate and reduced fat oxidation, factors expected to increase fat accumulation. METHODS:We used data collected from 80 children and adolescents (aged 6-15 years; n = 39 females) living in Vanuatu. Relative lower limb length, calculated as the ratio of lower limb length to stature, was used as a surrogate measure of each individual's early-life environmental conditions, with a shorter relative lower limb length considered indicative of greater adversity. Fasting resting metabolic rate (RMR) and respiratory quotient (RQ) were measured with indirect calorimetry, and a higher RQ value was considered indicative of a lower rate of fat oxidation. RESULTS:We found that, in a linear mixed-effects model including age, sex, and fat-free body mass as fixed effects and community and family as random effects, relative lower limb length was not significantly associated with RMR (p = 0.95). However, in a separate model, relative lower limb length was significantly negatively associated with RQ (p = 0.036), after accounting for the same fixed and random effects. CONCLUSIONS:The latter finding suggests that adverse environmental conditions during early life may lead to reduced fat oxidation, which has the potential to increase the risk of obesity later in life. This finding might partially explain the so-called double burden of malnutrition (the co-occurrence of undernutrition and obesity) currently affecting many low- and middle-income countries.

Objective Handgrip strength (HGS) provides a dynamic indicator of overall strength and physical fitness. Population-based investigations of anemia and iron deficiency as predictors of HGS are limited; most studies rely on elderly and/or clinical samples. We assessed iron deficiency, anemia, body mass index (BMI), and body fat percentage as predictors of HGS among a representative cross-sectional sample of adult residents of Matlab, Bangladesh.Methods We collected HGS, anthropometric measurements, and whole blood specimens from a representative, population-based sample of adults in Matlab. We used hemoglobin to identify anemia and soluble transferrin receptor to identify iron deficiency. We estimated mixed-effects generalized linear models of HGS.Results Iron deficiency, but not anemia, was negatively associated with HGS among both men and women. Among men, but not women, underweight BMI was negatively associated with HGS, and overweight BMI was positively associated with HGS.Conclusions Iron nutrition is important for muscles' capacity for work and overall physical fitness, regardless of the presence of anemia. Among men (but not women) in this setting, BMI categories seem to capture differences in muscle tissue as well as adiposity.

Background and objectives:The use of psychoactive substances appears to be a consistent behavior throughout human evolutionary history. In contemporary research, this is often attributed to the addictive properties of such substances; an evolutionary perspective offers a more nuanced view. We take the case of betel nut use in Bangladesh to investigate the relationship between betel quid and chronic health outcomes, and to consider local disease ecology and evolutionary explanations for consumption of this psychoactive substance. Methodology:We analyzed data from a random sample of 765 women and 499 men in Matlab, Bangladesh, to assess associations between betel quid use and anemia, type 2 diabetes (T2D), hypertension, and inflammation (C-reactive protein, CRP). Results:Betel quid use was associated with all health outcomes investigated. Use of betel quid was inversely associated with CRP (β = -0.34; P-value = .007). For other outcomes, there were important interactions between betel quid use and gender. A positive association with anemia (aOR: 2.56, CI: 1.62, 4.04) and inverse associations with diabetes and hypertension (aOR: 0.38, CI: 0.22, 0.66; aOR: 0.41, 1.03, respectively) were apparent among men, but not women (anemia: aOR: 1.03, CI: 0.72, 1.49; diabetes: aOR: 0.98, CI: 0.58, 1.65; hypertension: aOR: 1.25, CI: 0.85, 1.85). Conclusions and implications:Betel quid use was inversely associated with inflammation and, among men, positively associated with anemia and inversely associated with diabetes and hypertension. Together, these findings suggest that the use of betel quid, and possibly other addictive substances, may have been a behavioral adaptation to diverse socioecological challenges.

OBJECTIVES:Around 11% of U.S. children are diagnosed with attention-deficit/hyperactivity disorder (ADHD). One hypothesis for ADHD's relatively high prevalence is that behaviors associated with ADHD were advantageous in past environments where they were positively selected for. A previous study showed that an allele associated with ADHD-the 7R allele of the gene encoding the D(4) dopamine receptor (DRD4)-had a positive effect on the nutritional status of nomadic adult Ariaal men and a negative effect on settled adult men. We attempted to replicate this finding by analyzing the impact of DRD4 7R on children's nutrition and other household metrics in the Rendille, a population closely related to the Ariaal. METHODS:We genotyped 259 Rendille children aged 5-10 years for DRD4 7R and analyzed this against previously collected anthropometric and household data from two Rendille towns. Analyses were pre-registered (https://osf.io/p8yv2/) before the addition of the 7R genotype to the dataset. RESULTS:DRD4 7R was not associated with iron nutrition, indicated by transferrin receptor (TfR) concentration, height-for-age (HAZ) or weight-for-height Z-scores (WHZ), or with maternal education status. However, DRD4 7R was positively associated with household economic status (p = 0.047). CONCLUSIONS:The failure to replicate an association between DRD4 7R and nutritional status might be due to this sample being of children who are not yet substantially provisioning themselves. Given that children's genotypes are correlated with parents' genotypes, it is likely that the effects of the parents' genotypes, rather than the participating children's, explain the association between children's DRD4 7R genotype and household economic success.

Since we published "Field and Laboratory Methods in Human Milk Research" in 2013, human milk research has increased dramatically in both number and diversity of studies. Anthropological human biologists and biological anthropologists have played key roles in the realization of this research, arguing that evolutionary, developmental, and biocultural perspectives as essential for understanding variation in human milk. The purpose of this review is to highlight human biologists' and biological anthropologists' contributions to our understanding of human milk, often made in broadly collaborative research, as part of the 50th anniversary of the Human Biology Association. In this review, we identify three areas where human biologists have made major contributions: (1) understanding milk as a phenotype, (2) sex-differentiated milk synthesis, and (3) the cultural ecology of milk. We end this review by discussing future research directions and the applied and translational potentials of milk research, calling on human biologists to continue our leadership in the field in the decades to come.

BACKGROUND:Infants given mothers' milk have higher resistance against infections than formula-fed counterparts. This protection is likely multifactorial, with roles for both milk immune factors and nutrients, particularly under elevated nutritional and disease stress. AIM:This study evaluated several milk nutrients/immune factors to assess associations with infant infectious disease during a severe drought. SUBJECTS AND METHODS:The study analysed morbidity recall data from Kenyan mother-infant dyads surveyed during a historic drought (n 84). Predictors of interest in logistic regression models of infant infections included milk sIgA, lactoferrin, retinol, folate receptor-α, fat, protein, and lactose. Adjustment variables included dyadic demographic characteristics and maternal infection. Akaike Information Criterion guided model fit assessment. Interactions between variables were allowed in the best-fit model. RESULTS:In the best-fit model, lactose was inversely (OR 0.93; 90% CI 0.89, 0.97), and maternal infection was positively (OR 2.80; 90% CI 1.04, 7.52) associated with infant infection. Milk immune factors (sIgA, lactoferrin) were not included in the final models. CONCLUSION:Mothers' milk may protect infants against infection through a broad range of immune and nutrient components. In the context of severe drought with heightened nutritional and disease stress, lactose may protect against infection or decrease in the presence of an infection.