A vast new study connects plant-based diets with various health benefits, including in cardiovascular diseases and cancer [1].
What exactly is healthy eating?
Diet is one of the most powerful anti-aging interventions available today, but nutrition is also an extremely hard topic to analyze. Food we ingest contains tens of thousands of nutrients, and numerous confounding factors are at play. Most knowledge on this topic comes from populational studies, although many randomized controlled trials have been conducted as well. A new umbrella review seeks to add to our understanding of the effects of plant-based diets on cardiovascular diseases and cancer – two primary causes of death and disability worldwide.
At the beginning of their paper, the researchers note that the deleterious effects of “suboptimal diets”, which are rich in processed foods, salt, refined grains, and sugar, are well-known [2]. Avoiding those is a low bar, but then there is another choice: is it better to eat a plant-based diet, a well-balanced Mediterranean diet, or a ketogenic diet?
Numerous studies have suggested that plant-based diets may be superior to carnivorous or omnivorous ones [3]. On the other hand, concerns exist about nutrient and vitamin deficiencies. While this vast review does not give a definitive answer, it certainly brings together a lot of evidence.
Lipid profiles
This review starts with total cholesterol, an important metric of cardiovascular health. In general, the included studies and reviews found substantial decreases in total cholesterol in people on plant-based diets (both vegan and vegetarian) compared to a variety of other diets. One study found that the effect was even larger for people with high BMI.
Results for high-density lipoprotein cholesterol (HDL-C, which is usually considered beneficial) were less definitive. Several reviews found no difference between vegetarians and omnivores, both in normal weight and overweight people. However, another one, based on 51 studies, reported a slight advantage for plant-based diets.
Low-density lipoprotein cholesterol (LDL-C, which is usually considered harmful) is often considered more important for cardiovascular health than HDL-C. Seven out of ten relevant reviews found that vegetarian diets were associated with significantly lower levels of LDL-C, both in the general population and in diabetic patients. Four other reviews confirmed this for vegan diets compared to omnivores.
Most studies found that vegetarians had significantly reduced triglycerides compared to omnivores. However, one review did not find noticeable differences, and another one’s results were the opposite, that triglyceride levels in vegetarians were higher compared to meat eaters. One of the two reviews that dealt specifically with vegans reported a significant decrease in triglycerides versus omnivores, but the other one did not.
Three reviews among those analyzed had dealt with full lipid profiles rather than singular metrics such as triglycerides or LDL-C. This approach reduced the measurement and reporting differences between studies. All of them found significantly lower levels of total cholesterol, HDL-C, and LDL-C in subjects who followed plant-based diets.
Glucose metabolism and inflammation
Practically all relevant studies agreed on the benefits of plan-based diets for glucose metabolism. The researchers cited lower fasting blood glucose, lower glycated hemoglobin (HbA1c), which is a long-term metric of glucose control, and lower incidence of diabetes.
C-reactive protein (CRP) is the most popular marker of inflammation. Here, too, the results were almost unanimous, with all but one review showing significant CRP reductions in vegans and vegetarians compared to omnivores. Even in that remaining review, lower CRP was recorded for people who were on a vegetarian diet for more than two years.
Cardiovascular disease and cancer
In terms of blood pressure, vegans and vegetarians were again on top, with most studies reporting considerably less both systolic and diastolic blood pressure compared to the general population. One study also found a 33% decrease in the prevalence of hypertension. However, some studies failed to detect a significant difference.
Many studies considered the prevalence of cardiovascular and cerebrovascular events, with most finding diminished risks for plant-based diets. Generally, the effect was more pronounced for heart disease and less so for cerebrovascular outcomes. One study suggested that plant-based diets were advantageous for secondary prevention of cardiovascular diseases, and another one reported that the positive effects were greater in participants who had picked plant-based diets earlier in life.
The researchers also delved into cancer incidence. One review found an 8% reduction in overall cancer risk for vegetarians and 15% for vegans, compared to omnivores. Across all studies, the results were heterogeneous, with some reporting no significant associations, but overall, the risk of colorectal cancer seems to be the one most attenuated by plant-based diets.
Analyzing vast umbrella reviews can be difficult due to the heterogeneity in the design and quality of the included studies. However, this review did include many studies of relatively high quality. Importantly, while some of the studies found no significant correlations between health benefits and plant-based diets, virtually none reported negative associations.
Literature
[1] Capodici, A., Mocciaro, G., Gori, D., Landry, M. J., Masini, A., Sanmarchi, F., … & Guaraldi, F. (2024). Cardiovascular health and cancer risk associated with plant based diets: An umbrella review. PloS one, 19(5), e0300711.
[2] Afshin, A., Sur, P. J., Fay, K. A., Cornaby, L., Ferrara, G., Salama, J. S., … & Murray, C. J. (2019). Health effects of dietary risks in 195 countries, 1990–2017: a systematic analysis for the Global Burden of Disease Study 2017. The lancet, 393(10184), 1958-1972.
[3] Babalola, F., Adesuyi, A., David, F., Kolajo, B. B. A., Urhi, A., Akinade, O., … & Anugwom, G. O. (2022). A comprehensive review on the effects of vegetarian diets on coronary heart disease. Cureus, 14(10).