Regularly consuming a vegetarian diet was associated with modest, yet significant improvements in cardiometabolic risk factors beyond standard pharmacologic treatment in individuals with or at high risk of cardiovascular disease (CVD), according to findings from a newly published systematic literature review and meta-analysis.
The findings, based on analysis of data from 20 randomized controlled clinical trials (RCTs), demonstrated that a vegetarian diet consumed for at least 6 months was associated with significant reductions in LDL-C, HbA1c, and body weight in a vulnerable, high-risk population.
“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 men n n n n n n n n n n n n n dicine and health, at the University of Sydney, in Sydney, Australia.
Vegetarian diets of varying forms, excluding meat and sometimes eggs and dairy as well, continue to gain attention and popularity for both their health and environmental benefits, the authors wrote in JAMA Network Open. Wang and colleagues point out that several diabetes organizations recommend vegetarian diets based on accumulating evidence of their preventive effects against type 2 diabetes (T2D) as well as its metabolic complications.
While there is growing evidence of the benefits of vegetarian eating in primary CVD prevention in the general population, Wang et al say there is much less known about how effective the dietary pattern might be in individuals with or at high risk of CVD.
The objective of their meta-analysis was to assess the association of vegetarian diets with major cardiometabolic risk factors, examining RCTs measuring LDL-C, HbA1c, or systolic blood pressure (SBP).
The investigators performed systematic searches in Embase, MEDLINE, CINAHL, and CENTRAL from inception until July 2021. Of 7871 records screened, 29 (0.4%; 20 studies) met inclusion criteria. Two members of the investigative team independently extracted data including demographics, study design, sample size, and diet description, and performed risk of bias assessment.
For their analysis, the researchers 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.
According to the findings, the 20 studies included in the analysis were all published between 1990 and 2021 and comprised 1878 participants. Sample size ranged from 13 to 291 participants who had a mean age of 28 to 64 years. The mean duration of the vegetarian dietary intervention was 25.4 weeks. Of the included trials, 4 targeted people with CVDs, 7 focused on diabetes, and 9 included individuals with ≥2 CVD risk factors.
Energy restrictions were prescribed in several studies to support weight loss. The researchers reported that the most commonly prescribed diets were vegan, followed by lacto-ovo vegetarian diets and lacto-vegetarian diets.
The meta-analysis of LDL-C included 19 studies and found that compared with control diets, consumption of a vegetarian diet over a mean of 6 months was associated with a significant decrease in LDL-C of 6.6 mg/dL (95% CI, -10.1 to -3.1 mg/dL) 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).
Investigators analyzed 10 studies investigating HbA1c and found that consuming vegetarian diets for a mean duration of 6 months was associated with a decrease in HbA1c of 0.24% (95% CI, -0.40 to -0.07). Results of the meta-analysis of 16 trials evaluating the effect of a vegetarian diet consumed for 6 months on body weight showed weight decreased by 3.4 kg (95% CI, -4.9 to -2.0 kg).
The pooled effect size of a vegetarian diet on SPB based on a meta-analysis of 14 studies, however, 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.
Source: 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