Dietary interventions can lower diastolic blood pressure (BP), and a high-fiber diet can reduce diastolic but not systolic BP, according to a study in Gastroenterology.

The findings are based on a systematic review and meta-analysis that evaluated the effect of dietary interventions on the gut microbiota (GM) and outcomes related to cardiometabolic diseases (CMD).

Researchers performed a literature search on Ovid Medline and Ovid on July 6, 2020, for randomized or nonrandomized clinical trials that measured a component of CMD, including metabolic syndrome (MetSyn), type 2 diabetes (T2D), nonalcoholic fatty liver disease (NAFLD), and cardiovascular disease (CVD).


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A total of 21 studies were included, and all had a high risk for bias. The researchers pooled all randomized studies with an intervention group and control group and performed meta-analyses on the cardiometabolic outcomes, which included 6 studies with 8 intervention groups. Dietary intervention was defined as a change in dietary macronutrient composition and/or dietary pattern.

The meta-analysis showed that only diastolic BP decreased after the dietary interventions, with a mean difference of -3.63 mm Hg (95% CI, -7.09 to -0.17; I2=0%; P =.04), compared with the control group.

A trend was observed toward lower triglyceride levels (mean difference [95% CI], -0.26 mmol/L [-0.58 to 0.06]; I2=59%; P =.11) and lower fasting plasma glucose levels (-0.18 mmol/L [-0.39 to 0.04]; I2=0%, P =.11), after dietary interventions.

The study authors also conducted meta-analyses stratified to pre-specified CMD conditions. In studies that only assessed participants with MetSyn, none of the outcomes was significantly different between the intervention and control groups. In 2 studies involving patients with NAFLD, dietary interventions appeared to trend toward higher HDL vs the control group (mean difference [95% CI], 0.10 [0.00 to 0.20]; I2=0%; P =.06). Studies that included patients with T2D did not show any differences between the groups.

The researchers also assessed the effect of specific dietary interventions on CMD. In the 2 studies that used a high-fiber dietary intervention, the mean triglyceride decrease was -0.69 mmol/L (95% CI, -1.36 to -0.02; I2=59%; P =.04) compared with the control group.

The researchers noted that the included studies were heterogeneous in medication use, disease progression, antibiotic use, and dietary interventions, which limits the generalizability of their results. In addition, the duration of interventions was also different among the studies, which may confound gut microbiota findings.

“This study shows that dietary microbiome interventions can be effective to improve cardiometabolic disease parameters,” the study authors noted. “However, the observed high risk of methodological bias calls for new standards in the microbiome field.”

Disclosure: One of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

Reference

Attaye I, Warmbrunn MV, Boot ANAF, et al. A systematic review and meta-analysis of dietary interventions modulating gut microbiota and cardiometabolic diseases—striving for new standards in microbiome studies. Gastroenterology. Published online February 10, 2022. doi:10.1053/j.gastro.2022.02.011