Vegetarian/vegan diets associated with lower cancer, cardiovascular risk
While an umbrella review found numerous improvements in biomarkers with diets that exclude meat or all animal products, the strength of evidence for these diets was limited, the review's authors concluded.
Plant-based diets appeared to reduce cardiometabolic risk factors and diseases, cancers, and overall mortality, but the strength of evidence was significantly limited by study heterogeneity, an umbrella review found.
To assess the impact of animal-free and animal product-free diets on the risk factors for morbidity and mortality, researchers conducted an umbrella analysis of reviews, systematic reviews, and meta-analyses published from January 2000 to June 2023. Papers focused strictly on vegans, lacto-vegetarians, ovo-vegetarians, or lacto-ovo-vegetarians. Results were published by PLOS One on May 15.
Overall, vegetarian and vegan diets were significantly associated with improved total and low-density lipoprotein cholesterol levels, glycemic control, body weight/mass, inflammation (as measured by C-reactive protein levels), and risk of ischemic heart disease and cancer. Vegetarian diets were also associated with lower mortality from cardiovascular diseases. No difference in the risk of gestational diabetes and hypertension were reported in pregnant women following vegetarian diets. The diets' effects on levels of high-density lipoprotein cholesterol and triglycerides and systolic and diastolic blood pressure remain debatable, the authors noted.
"It should be remarked that, in the majority of the cases, people adopting plant-based diets are more prone to engage in healthy lifestyles that include regular physical activity, reduction/avoidance of sugar-sweetened beverages, alcohol and tobacco, that, in association with previously mentioned modification of diet, lead to the reduction of the risk of ischemic heart disease and related mortality, and, to a lesser extent, of other [cardiovascular diseases]," the study authors wrote.
They judged the quality of the included studies as average. However, the authors noted a high heterogeneity of the study populations by sample size, demography, geographical origin, dietary patterns, and other lifestyle confounders.
The review found that eating red processed meats was associated with gastrointestinal cancers and noted that vegetarians might have also received protection from increased consumption of fruits and vegetables. Vegetarians also ate less refined grains, added fats, sweets and snacks, and caloric beverages, which may have reduced hyperinsulinemia, one of the possible factors for colorectal cancer risk.
"This dietary pattern should not be regarded as a universal principle, as varying tendencies have been observed among vegetarians and vegans in different studies," said the study authors, cautioning that "potential risks associated with insufficient intake of vitamin and other elements due to unbalanced and/or extremely restricted dietary regimens, together with specific patient needs should be considered."