Plant-Based Diets: Good for You and the Climate

An in-depth evaluation of random trials conducted since 1982 has revealed that both vegan and vegetarian diets lead to a decline in cholesterol and fat concentrations in the bloodstream. 

The research, published in the European Heart Journal, posits that adherence to plant-based diets plays a significant role in minimizing arterial obstructions, thereby reducing the likelihood of cardiovascular diseases like strokes and heart attacks.

The study, which analyzed 30 randomized trials involving 2,372 participants from 1982 to 2022, compared the impact of vegetarian or vegan diets against omnivorous diets on various cholesterol levels: total cholesterol, low-density lipoprotein cholesterol (LDL or 'bad' cholesterol), triglycerides (a type of blood fat), and apolipoprotein B (apoB – a protein essential for transporting fat and cholesterol in the blood, and a reliable measure of harmful fats and cholesterol in the body). This research fills a gap in prior meta-analyses that did not factor in variables such as continent, age, body mass index, and health status, or focus specifically on diet's influence on apoB concentrations.

The study, led by Professor Ruth Frikke-Schmidt, Chief Physician at Rigshospitalet in Copenhagen, Denmark, in collaboration with medical student Caroline Amalie Koch and Dr. Emilie Westerlin Kjeldsen, discovered that vegetarian and vegan diets corresponded with a 14% reduction in all lipoproteins that cause arterial blockages, as indicated by apoB levels. This reduction is comparable to a third of the effect of cholesterol-lowering medications like statins, and could result in a 7% decrease in cardiovascular disease risk for someone who maintains a plant-based diet for five years. Statin treatment surpasses plant-based diets in reducing fats and cholesterol, but combining both methods can yield an even greater beneficial outcome.

The team also stressed the significantly reduced risk of cardiovascular disease from blocked arteries for those who adopt vegetarian or vegan diets early in life, irrespective of location, age, body mass index range, or health status.

The 30 studies assigned participants to either a plant-based diet or an omnivorous diet for periods ranging from ten days to five years, averaging 29 weeks. Compared to those on an omnivorous diet, individuals on a plant-based diet experienced an average 7% reduction in total cholesterol, a 10% decrease in LDL cholesterol, and a 14% reduction in apoB levels from levels documented at the start of the studies.

Prof. Frikke-Schmidt reveals, "Significant health benefits were witnessed among individuals of various body sizes, following both vegetarian and vegan diets." Cardiovascular disease (CVD) is a global concern, causing over 18 million deaths worldwide annually. As per the UN's Sustainable Development Agenda, the aim is to decrease premature deaths from diseases like CVD by one-third by 2030, with dietary habits playing a crucial role.

"Recent surveys indicate that if affluent nations adopt plant-based diets, this could potentially decrease greenhouse gas emissions by 35%-49%. Our studies present strong evidence that plant-based diets are beneficial for people of different sizes, ages, and health conditions," Prof. Frikke-Schmidt adds. "With populations aging worldwide, the expense of treating age-related diseases like atherosclerotic cardiovascular disease is on the rise. Plant-based diets offer a solution for sustainable food production while simultaneously reducing the burden of cardiovascular diseases. A diverse, plant-heavy diet, consumed in moderation and paired with water, is ideal."

Despite the lack of studies comparing fish-based diets to omnivorous ones in their meta-analysis, Prof. Frikke-Schmidt and her team acknowledge the well-established benefits of the Mediterranean diet, which is rich in both plant-based foods and fish.

In an independent editorial, Professors Kevin Maki and Carol Kirkpatrick, who were not part of the research, stated, "The findings by Koch and team contribute to the growing evidence that healthy vegan and vegetarian diets have positive effects on LDL cholesterol and atherogenic lipoproteins, which could reduce the risk of atherosclerotic CVD. While it's not mandatory to completely eliminate foods like meat, poultry, and fish, reducing consumption of these is a viable option for those who prefer it."

The strength of this study lies in it being the most extensive systematic review of the topic, and the first to encompass apoB. However, it does have limitations, such as the relatively small size of the individual randomized controlled trials, the short duration of the diets, and the lack of participant blinding, which could potentially influence other behaviors that affect cholesterol and fat levels.

Reference: “Vegetarian or vegan diets and blood lipids: a meta-analysis of randomized trials” by Caroline A Koch, Emilie W Kjeldsen and Ruth Frikke-Schmidt, 24 May 2023, European Heart Journal.