A randomized controlled trial of the effects of whole grains versus refined grains diets on the microbiome in pregnancy

Abstract

Dietary whole grain consumption has been postulated to have metabolic benefits. The purpose of this study was to compare a pregnancy diet containing 75% of total carbohydrates as refined grains with a diet of 75% of total carbohydrates as whole grains for pregnancy outcomes and effects on the microbiome. Gestational weight gain, glucose tolerance and newborn outcomes were measured on 248 enrolled compliant women from whom a subset of 103 women consented to give 108 vaginal and 109 anal swabs. The data presented here are limited to the patients from whom the vaginal and anal swabs were obtained in order to study the microbiome. A microbiome-16SrRNA survey-was characterized in these samples. Samples and measurements were obtained at the first obstetrical visit, before beginning a prescribed diet (T1-baseline) and after 17-32 weeks on the prescribed diet (T3). Food frequency questionnaires and total plasma alkylresorcinols were used as a measure of whole grain consumption. There were no dietary differences in maternal weight gain, birth weight, or glucose tolerance test. Mothers consuming the whole grains diet showed a trend of gestational decrease in vaginal bacterial alpha diversity, with increasing Lactobacillus-dominance. No significant difference was observed for the anal microbiome. The results suggest that diet modulations of the vaginal microbiome during gestation may have important implications for maternal and neonatal health and in the intergenerational transfer of maternal microbiome. Trial registration: ClinicalTrials.gov Identifier: NCT03232762.

Figure 1

Alpha diversity in the vaginal and anal microbiota of 103 mothers. Faith PD, Observed ASVs, and Shannon index was presented respectively, Kruskal–Wallis test performed between the three groups. (a) Vaginal microbiome. (b) Anal microbiome.

Figure 2

LEfSe cladogram of differing taxa. Significantly enriched taxa colored in purple for refined grains diet, green for whole grains diet. g_ for genus level, f_ for family level, o_ for order level, c_ for class level, and p_ for phylum level. (a) Vaginal overrepresented taxa in each group. (b) Anal overrepresented taxa in each group.

Figure 3

Vaginal and anal microbiome beta diversity. PCoA generated on weighted Unifrac distance. (a) Vaginal, (b) anal. Table shows the PERMANOVA result effect between baseline, whole grains T3, and refined grains T3. Ellipses represent 95% CI of center of each group under multivariate t-distribution.