Abstract Body: Background: The Dietary Approaches to Stop Hypertension for Diabetes (DASH4D) trial showed that a DASH-style diet vs. typical US comparison diet improved glycemia in adults with type 2 diabetes. The biological mechanism may include microbial production of short-chain fatty acids (SCFAs), which have been associated with improved glycemia.
Objective: The aim of this study is to evaluate the effects of a DASH-style diet vs. comparison diet on SCFAs in stool and plasma. We hypothesized that the DASH-style diet increases SCFAs.
Methods: DASH4D is a randomized 4-period crossover feeding study among adults with type 2 diabetes, a systolic blood pressure of 120-159 mmHg, and a diastolic blood pressure of <100 mmHg. The DASH4D diet is a DASH-style diet modified for adults with type 2 diabetes (i.e., with lower carbohydrates, higher unsaturated fat, and lower potassium than the original DASH diet). Participants were randomized to a sequence of four 5-week diets: (1) DASH4D with lower sodium, (2) DASH4D with higher sodium, (3) comparison diet with lower sodium, and (4) comparison diet with higher sodium. Our primary interest was DASH4D vs. comparison diets. Outcomes were SCFAs measured in stool and plasma, collected at baseline and at the end of each diet period. We measured SCFAs in plasma and in feces using gas chromatography-mass spectrometry. We normalized SCFAs using log transformation. We fit linear mixed effects models to examine mean log-transformed SCFAs at the end of each diet period.
Results: There were 97 participants with plasma samples (and of those, 83 with fecal samples) from both pre-randomization and 2 or more feeding periods. Of these 97 participants, 66% were female and 89% self-identified as Black. Mean age was 67 (SD 8.9) years. There was no evidence interaction between diet and sodium level, so we present unstratified results. Relative to the comparison diet, the DASH4D diet increased plasma acetate by 8.7% (95%CI: 1.3%-16.7%). No other SCFAs were changed in the plasma or in the stool (Fig. 1). Sodium level of diet did not affect SCFAs in plasma or stool (Fig. 2).
Conclusion: In adults with type 2 diabetes, the DASH4D diet increased plasma acetate, but not other plasma SCFAs. Null effects on stool SCFAs are consistent with animal studies that show SCFAs may be reabsorbed in the colon when plasma SCFAs increase. Research is needed to understand if changes in plasma acetate mediates the health effects (e.g., glycemic effects) of a DASH-style diet.