Umbrella review captures impact of plant-based diets on cancer, cardiometabolic diseases

Key takeaways:

• Plant-based diets were tied to reductions in several health measures, like body weight and cholesterol.
• However, researchers urged caution when recommending these diets due to study limitations.

An umbrella review of 2 decades of research showed that vegan and vegetarian diets were associated with a greater lipid profile and reduced risk for cancer and death.

Healthy plant-based diets have previously been tied to lower risks for cancer and other chronic conditions. However, these analyses were limited by study heterogeneity, and other research has highlighted potential consequences of vitamin deficiencies linked to these diets, “especially more restrictive ones and in critical periods of life, like pregnancy and early childhood,” Angelo Capodici, a PhD student at the Sant'Anna School of Advanced Studies, in Italy, and colleagues wrote in PLOS ONE.

The umbrella review included 48 average-quality reviews and meta-analyses published from 2000 to June 2023.

Capodici and colleagues found that vegetarian and vegan diets were associated with better markers of health, including a better lipid profile, glycemic control, inflammation, body weight and BMI, as well as a lower risk for ischemic heart disease and cancer. Additionally, the vegetarian diet was associated with a lower risk for mortality from CVD.

For example, one study found that vegetarians had a significantly lower risk for ischemic heart disease (RR = 0.71; 95% CI, 0.56-0.87) vs. nonvegetarians, and another found a lower incidence for total stroke among vegetarians (HR = 0.66; 95% CI, 0.45-0.95).

When looking at cancer, one analysis found a significantly lower overall and total cancer incidence in vegetarians vs. omnivores (RR = 0.82; 95% CI, 0.67-0.97), whereas another reported lower incidence for prostate cancer (HR = 0.57; 95% CI, 0.43-0.76) and colorectal cancer (HR = 0.73; 95% CI, 0.54-0.99).

The researchers also highlighted a study that showed reductions in HbA1c (mean difference [MD] = 0.29%; 95% CI, 0.45 to 0.12) and blood fasting glucose (MD = 0.56 mmol/L; 95% CI, 0.99 to 0.13) among vegetarians compared with nonvegetarians.

A review and meta-analysis of 19 studies additionally found greater total cholesterol (weighted MD = 1.72 mmol/L; 95% CI, 1.93 to 1.51) reduction among vegans vs. omnivores.

“A much more limited body of literature suggested vegetarian, but not vegan diets also reduce [apolipoprotein B] levels further improving the lipid profile,” Capodicil and colleagues wrote.

They added that plant-based diets did not influence the risk for pregnancy-induced hypertension or gestational diabetes mellitus.

However, the researchers pointed out the review was limited by the original studies’ sample sizes, demographic features and dietary patterns.

Because of that, along with “potential risks associated with insufficient intake of vitamin and other elements due to unbalanced and/or extremely restricted dietary regimens,” they suggested caution when promoting plant-based diets on a larger scale.