Publications by Year: 2020

BACKGROUND: Short chain fatty acids (SCFAs; e.g., acetate, propionate, and butyrate) are produced by microbial fermentation of fiber in the colon. Evidence is lacking on how high-fiber diets that differ in macronutrient composition affect circulating SCFAs.

OBJECTIVES: We aimed to compare the effects of 3 high-fiber isocaloric diets differing in %kcal of carbohydrate, protein, or unsaturated fat on circulating SCFAs. Based on previous literature, we hypothesized that serum acetate, the main SCFA in circulation, increases on all high-fiber diets, but differently by macronutrient composition of the diet.

METHODS: OmniHeart is a randomized crossover trial of 164 men and women (≥30 y old); 163 participants with SCFA data were included in this analysis. We provided participants 3 isocaloric high-fiber (∼30 g/2100 kcal) diets, each for 6 wk, in random order: a carbohydrate-rich (Carb) diet, a protein-rich (Prot) diet (protein predominantly from plant sources), and an unsaturated fat-rich (Unsat) diet. We used LC-MS to quantify SCFA concentrations in fasting serum, collected at baseline and the end of each diet period. We fitted linear regression models with generalized estimating equations to examine change in ln-transformed SCFAs from baseline to the end of each diet; differences between diets; and associations of changes in SCFAs with cardiometabolic parameters.

RESULTS: From baseline, serum acetate concentrations were increased by the Prot (β: 0.24; 95% CI: 0.12, 0.35), Unsat (β: 0.21; 95% CI: 0.10, 0.33), and Carb (β: 0.12; 95% CI: 0.01, 0.24) diets; between diets, only Prot compared with Carb was significant (P = 0.02). Propionate was decreased by the Carb (β: -0.10; 95% CI: -0.16, -0.03) and Unsat (β: -0.10; 95% CI: -0.16, -0.04) diets, not the Prot diet; between diet comparisons of Carb vs. Prot (P = 0.006) and Unsat vs. Prot (P = 0.002) were significant. The Prot diet increased butyrate (β: 0.05; 95% CI: 0.00, 0.09) compared with baseline, but not compared with the other diets. Increases in acetate were associated with decreases in insulin and glucose; increases in propionate with increases in leptin, LDL cholesterol, and blood pressure; and increases in butyrate with increases in insulin and glucose, and decreases in HDL cholesterol and ghrelin (Ps < 0.05).

CONCLUSIONS: Macronutrient composition of high-fiber diets affects circulating SCFAs, which are associated with measures of appetite and cardiometabolic health. This trial was registered at clinicaltrials.gov as NCT00051350.

OBJECTIVES: To examine the effects of high-fiber, isocaloric, macronutrient substitutions on bloating.

METHODS: The OmniHeart study is a randomized 3-period crossover feeding trial conducted from April 2003 to June 2005. Participants were provided 3 isocaloric versions of high-fiber (∼30 g per 2,100 kcal) diet, each different in carbohydrate, protein, and unsaturated fat composition. Each feeding period lasted for 6 weeks with a 2- to 4-week washout period between diets. Participants reported the presence and severity of bloating at baseline (participants were eating their own diet) and at the end of each feeding period.

RESULTS: One hundred sixty-four participants were included in the analysis (mean age: 53.1 years; 45% women; 55% black). The prevalence of bloating at baseline and at the end of the carbohydrate-rich, protein-rich, and unsaturated fat-rich diet period was 18%, 24%, 33%, and 30%, respectively. Compared with baseline, the relative risk of bloating for the carbohydrate-rich, protein-rich, and unsaturated fat-rich high-fiber diet was 1.34 (95% confidence interval [CI]: 0.93, 1.92), 1.78 (95% CI: 1.32, 2.40), and 1.63 (95% CI: 1.17, 2.26), respectively. The protein-rich diet increased the risk of bloating more than the carbohydrate-rich diet (relative risk = 1.40; 95% CI: 1.03, 1.88). Bloating did not significantly vary between protein-rich vs unsaturated fat-rich or unsaturated fat-rich vs carbohydrate-rich diets. Black participants compared with non-black participants had a higher risk of bloating after all 3 versions of the high-fiber OmniHeart diet (P-value for interaction = 0.012).

DISCUSSION: Substitution of protein with carbohydrate may be an effective strategy to decrease bloating among individuals experiencing gastrointestinal bloating from a high-fiber diet.

The Environmental Influences on Child Health Outcomes (ECHO) Program will evaluate environmental factors affecting children's health (perinatal, neurodevelopmental, obesity, respiratory, and positive health outcomes) by pooling cohorts composed of >50,000 children in the largest US study of its kind. Our objective was to identify opportunities for studying chemicals and child health using existing or future ECHO chemical exposure data. We described chemical-related information collected by ECHO cohorts and reviewed ECHO-relevant literature on exposure routes, sources, and environmental and human monitoring. Fifty-six ECHO cohorts have existing or planned chemical biomonitoring data for mothers or children. Environmental phenols/parabens, phthalates, metals/metalloids, and tobacco biomarkers are each being measured by ≥15 cohorts, predominantly during pregnancy and childhood, indicating ample opportunities to study child health outcomes. Cohorts are collecting questionnaire data on multiple exposure sources and conducting environmental monitoring including air, dust, and water sample collection that could be used for exposure assessment studies. To supplement existing chemical data, we recommend biomonitoring of emerging chemicals, nontargeted analysis to identify novel chemicals, and expanded measurement of chemicals in alternative biological matrices and dust samples. ECHO's rich data and samples represent an unprecedented opportunity to accelerate environmental chemical research to improve the health of US children.

Increasing diverse engagement in the Society for Epidemiologic Research (SER) will positively impact the field of epidemiology. As the largest and longest-running epidemiologic society in North America, SER has long been a pioneer in promoting diversity and inclusion. A recent survey of SER members, however, showed there is still room for improving diversity, inclusion, representation, and participation in the Society. In this commentary, as members of both the SER and the Johns Hopkins Bloomberg School of Public Health Department of Epidemiology's Inclusion, Diversity, Equity, Anti-Racism, and Science (Epi IDEAS) Working Group, we recommend 4 goals for the SER Annual Meeting and beyond: 1) convene epidemiologic researchers with diverse backgrounds and ideas; 2) promote an inclusive environment at the SER Annual Meeting; 3) develop, compile, and disseminate best practices to honor diversity in epidemiologic research; and 4) increase prioritization of health disparities research and methods. We also suggest strategies for achieving these goals so that SER can better include, support, and elevate members from historically disadvantaged groups. While our recommendations are tailored specifically to SER, the greater epidemiologic and academic communities could benefit from adopting these goals and strategies within their professional societies and conferences.

IMPORTANCE: Maternal preeclampsia may be one of the early risk factors for childhood and adolescence elevated blood pressure (BP). It is unknown whether the intergenerational association between maternal preeclampsia and offspring BP differs by cord blood vitamin D levels.

OBJECTIVE: To assess the associations between maternal preeclampsia and offspring systolic BP (SBP) across childhood and adolescence and to test whether these associations vary by cord blood 25-hydroxyvitamin D [25(OH)D] concentrations (a biomarker of in utero vitamin D status).

DESIGN, SETTING, AND PARTICIPANTS: This prospective cohort study analyzed 6669 SBP observations from 754 mother-child pairs from the Boston Birth Cohort, who were enrolled from December 1998 to June 2009. Data were analyzed from October 2019 to March 2020.

EXPOSURES: Physician-diagnosed maternal preeclampsia. Plasma 25(OH)D concentrations measured in cord blood samples collected at delivery.

MAIN OUTCOMES AND MEASURES: Repeated SBP measures between 3 and 18 years of age. The SBP percentile was calculated based on the 2017 American Academy of Pediatrics hypertension guidelines. Mean difference in SBP percentile in children born to mothers with vs without preeclampsia was compared across different cord blood 25(OH)D levels.

RESULTS: There were 6669 SBP observations from the 754 children; 50.0% were female and 18.6% were born preterm. Of the 754 mothers, 62.2% were Black and 10.5% had preeclampsia. Median cord blood 25(OH)D was 12.2 (interquartile range, 7.9-17.2) ng/mL. Maternal preeclampsia was associated with 5.34 (95% CI, 1.37-9.30) percentile higher SBP after adjusting for confounders. This association varied by quartiles of cord blood 25(OH)D concentrations: the differences in SBP percentile comparing children born to mothers with vs without preeclampsia were 10.56 (95% CI, 2.54-18.56) for quartile 1 (lowest), 7.36 (95% CI, -0.17 to 14.88) for quartile 2, 4.94 (95% CI, -3.07 to 12.96) for quartile 3, and -1.87 (95% CI, -9.71 to 5.96) for quartile 4 (highest). When cord blood 25(OH)D was analyzed continuously, children born to mothers with preeclampsia had 3.47 (95% CI, 0.77-6.18) percentile lower SBP per 5 ng/mL 25(OH)D increment. These associations did not differ by child sex or developmental stages.

CONCLUSIONS AND RELEVANCE: In this study of a US high-risk birth cohort, maternal preeclampsia was associated with higher offspring SBP from early childhood to adolescence. These associations were attenuated by higher cord blood 25(OH)D levels in a dose-response fashion. Additional studies, including clinical trials, are warranted.