Vegetarian Diets May Improve Cardiometabolic Outcomes in High-Risk Patients

Tian Wang, APD, RD

Credit: ResearchGate

Consumption of a vegetarian diet may have modest, but significant improvements in cardiometabolic outcomes beyond standard therapy in individuals with or at high risk of cardiovascular diseases (CVDs), according to new research.¹

The systematic review and meta-analysis of 20 randomized controlled trials (RCTs) suggested a vegetarian diet in these high-risk patients was associated with significant improvements in low-denisty lipoprotein cholesterol (LDL-C), hemoglobin A1c (HbA1c), and body weight.

“Vegetarian diets were most effective in glycemic control among people with type 2 diabetes (T2D), and led to favorable changes in weight in people at high risk of CVD and in those with T2D, suggesting that vegetarian diets might have a synergistic (or at least nonantagonistic) use in potentiating the effects of optimal drug therapy in the prevention and treatment of a range of cardiometabolic diseases,” wrote the investigative team, led by Tian Wang, APD, RD, from the Charles Perkins Centre, faculty of medicine and health, at the University of Sydney.

Poor diet has been linked to an elevated risk of CVD morbidity and mortality. Dietary guidelines released by the American Heart Association in 2021 indicated the importance of dietary patterns rich in minimally processed plant foods, fish, and seafood, and low-fat dairy products. On the other hand, diabetes organizations have recommended the consumption of a well-balanced vegetarian diet in line with evidence suggesting their effect at preventing T2D and its metabolic complications.

There are accumulating data from meta-analyses of RCTs showing a role of vegetarian diet in the primary prevention of CVDs in the general population. However, little is known regarding their effectiveness on those with or at high of CVDs. The objective of the current meta-analysis was to assess the association of vegetarian diets with major cardiometabolic risk factors, with eligible RCTs measuring LDL-C, HbA1c, or systolic blood pressure (SBP).

A systematic search was performed in Embase, MEDLINE, CINAHL, and CENTRAL from inception until July 2021. Of 7871 records screened, 29 (0.4%; 20 studies) met inclusion criteria. In the investigative team, 2 reviewers independently extracted data including demographics, study design, sample size, and diet description, and performed risk of bias assessment.

The analysis used a random-effects model to assess mean changes in LDL-C, HbA1c, SBP, and body weight between preintervention and postintervention for the primary outcomes. Secondary outcomes included change in body weight and energy intake.

The 20 studies were conducted across the US, Asia, Europe, or New Zealand, involving 1878 participants, and the mean duration of intervention was 25.4 weeks. Of the included trials, 4 targeted people with CVDs, 7 focused on diabetes, and 9 included individiauls with ≥2 CVD risk factors.

Upon analysis of 19 studies, the consumption of a vegetarian diet was found to be associated with a significantly decreased LDL-C by 6.6 mg/dL (95% CI, -10.1 to -3.1 mg/dL) over a mean of 6 months beyond that achieved with standard therapy. The most consistent reduction was observed among people at high risk of CVDs (-9.1 mg/dL; 95% CI, -12.7 to -5.5 mg/dL).

An analysis of 10 studies investigating HbA1c found that consuming vegetarian diets was associated with decreased HbA1c by 0.24% (95% CI, -0.40 to -0.07) in a mean 6 months of intervention. Results from 16 trials included in a meta-analysis of body weight showed weight decreased by 3.4 kg in a mean 6 months of intervention in individuals randomized to vegetarian diets (95% CI, -4.9 to -2.0 kg).

However, a meta-analysis of 14 studies revealed the pooled effect size of vegetarian diets on SBP was not statistically significant (-0.1 mmHg; 95% CI, -2.8 to 2.6 mmHg). In the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) assessment, investigators found the level of evidence was rated moderate for LDL-C and HbA1c reduction and low for SBP and weight reduction.

“Well-designed nutrition clinical trials with comprehensive dietary information are warranted to investigate the full effect of high-quality vegetarian diets in combination with optimal pharmacological therapy in people with CVDs,” the team wrote.

References

1. Wang T, Kroeger CM, Cassidy S, et al. Vegetarian Dietary Patterns and Cardiometabolic Risk in People With or at High Risk of Cardiovascular Disease: A Systematic Review and Meta-analysis. JAMA Netw Open. 2023;6(7):e2325658. doi:10.1001/jamanetworkopen.2023.25658
2. Lichtenstein AH, Appel LJ, Vadiveloo M, etal. 2021 dietary guidance to improve cardiovascular health: a scientific statement from the American Heart Association. Circulation. 2021;144(23):e472-e487. doi:10.1161/CIR. 0000000000001031