Plant-based diets have become more than a trend; they are now a cornerstone of many health recommendations. Suboptimal diets, rich in processed meats and sugars, are known culprits behind the soaring rates of several illnesses. In contrast, diets abundant in vegetables, fruits, legumes, and whole grains offer a protective shield against these diseases. The shift towards vegetarian and vegan diets, driven by health, ethical, and environmental concerns, is gaining momentum globally.

But how much of that is based on actual science? According to a new study — a lot of it. An umbrella review looked at 48 studies published from 2000 to 2023 and concluded that plant-based diets really are better for you.

Disease and diet

Cardiovascular diseases (CVDs) and cancer are two of the biggest challenges in global health. These conditions not only steal lives but also diminish the quality of life for millions worldwide. While genetics and other factors play a role, our diet is a powerful weapon we can wield to combat these diseases. A growing body of evidence suggests that plant-based diets, particularly vegetarian and vegan options, could be the key to unlocking a healthier future.

Several studies have suggested this. However, individual studies usually look at the impact of diet on one condition or a small set of conditions.

Angelo Capodici and colleagues from University of Bologna, Italy, wanted to quantify how much plant diets help on a more general level. They conducted an “umbrella review,” where they evaluated other reviews and meta-analyses to determine how plant-based diets affect the risk factors for cardiometabolic diseases and cancer. The study excluded interventional trials and focused on observational data to provide a clearer picture of diet-related health outcomes.

Key Findings: Cardiovascular Benefits

The new study analyzed several different health markers.

1. Cholesterol and Lipid Profiles: The review confirms that plant-based diets significantly improve lipid profiles. Individuals adhering to vegetarian and vegan diets exhibit lower levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) — “bad cholesterol”. The reductions in TC and LDL-C, both critical markers for heart disease, are profound and consistent across numerous studies.
2. Inflammation and Body Weight: Plant-based diets are also associated with lower levels of inflammation and reduced body weight, which are both crucial factors in mitigating the risk of cardiovascular diseases. Lower C-reactive protein (CRP) levels among vegetarians and vegans indicate reduced inflammation. And their typically lower body mass index (BMI) suggests a healthier body weight profile.
3. Blood Pressure: While the impact on blood pressure is mixed, some studies within the review highlight significant reductions in both systolic and diastolic blood pressure among those following plant-based diets. This reduction is vital for cardiovascular health, given the strong link between high blood pressure and heart disease.
4. Glycemic Control: Plant-based diets also contribute to better glycemic control, evidenced by lower fasting glucose and glycosylated hemoglobin (HbA1c) levels. These improvements suggest a reduced risk of developing type 2 diabetes, which is a significant risk factor for cardiovascular disease.

Perhaps most excitingly, the review hints at a potential link between plant-based diets and longevity. Vegetarians seem to have a lower risk of dying from ischemic heart disease and other circulatory diseases. While more research is needed to fully understand this connection, it’s a tantalizing prospect.

Cancer Risk Reduction

The review also sheds light on the protective effects of plant-based diets against cancer. High intake of fiber, antioxidants, and phytonutrients found in plants contributes to a lower risk of various cancers. This connection was notable with those affecting the digestive system.

1. Colorectal Cancer: Plant-based diets are notably effective in reducing the risk of colorectal cancer, with evidence suggesting an 8-15% lower risk compared to omnivorous diets. This reduction is attributed to the high fiber content in plant foods, which promotes a healthy gut environment.
2. Other Cancers: While the evidence is strongest for colorectal cancer, there are indications that plant-based diets may also reduce the risk of other cancers, such as prostate and pancreatic cancers. These benefits are likely due to the overall healthier dietary patterns of vegetarians and vegans, which include lower consumption of processed meats and higher intake of protective nutrients.

Not everything is necessarily rosy for plant-based diets

Some groups benefitted from plant-based diets more than others. Factors such as geographic differences, dietary adherence, and lifestyle habits can influence the outcomes. For instance, among pregnant women specifically, vegetarian diets showed no difference in risk of gestational diabetes and hypertension compared to non-plant-based diets.

Also, despite the clear benefits, the review also highlights potential risks associated with plant-based diets — particularly if they are not well-planned. Nutritional deficiencies, such as vitamin B12, iron, and omega-3 fatty acids, can occur in more restrictive diets. Pregnant women, children, and other vulnerable groups need to ensure they are getting adequate nutrition to avoid health complications.

The bottom line

Isolating the effect of diet from all other lifestyle and genetic factors is always challenging. However, the analysis consistently found that that vegetarian and vegan diets are linked to a healthier profile across various risk factors for CVDs and cancer, including blood pressure, blood sugar control, and body mass index. These diets are associated with a reduced risk of ischemic heart disease, gastrointestinal and prostate cancers, and cardiovascular disease mortality.

More research is needed to explore the impact of plant-based diets on specific health markers and to address potential nutrient deficiencies. However, the evidence seems to strongly indicate that plant-based diets have a positive health impact.

Importantly, you don’t need to adopt an entirely plant-based diet to reap these benefits. Even reducing meat consumption and increasing the intake of plant-based foods can significantly improve health, demonstrating that small, manageable dietary changes can make a substantial difference.

Journal Reference: Capodici A, Mocciaro G, Gori D, Landry MJ, Masini A, Sanmarchi F, et al. (2024) Cardiovascular health and cancer risk associated with plant based diets: An umbrella review. PLoS ONE 19(5): e0300711. https://doi.org/10.1371/journal.pone.0300711