Introduction

Diets based primarily on plants have long been shown to improve environmental and physical health. The degree of restriction placed on foods derived from animals is one reason for these benefits. Compared to diets high in meat, plant-based diets furthermore and usually lower the lifetime risk of developing several chronic diseases.¹

Vegetarian diets are plant-based diets that focus mostly on a variety of plant foods and exclude any form of animal flesh, including meat, poultry, seafood, and their derivatives. The distinction between vegan diets and lacto-ovo-vegetarian diets is the inclusion of milk, eggs, and their derivatives. A vegetarian diet consists of grains, legumes, fruits, vegetables, nuts, and seeds, among other plant foods. This decision was made for ethical, health, and environmental reasons.²

Vegetarian diets and health

Compared to omnivorous diets, vegetarians have been shown to have superior cardiovascular outcomes. These outcomes include a lower risk of ischemic heart disease-related morbidity and mortality, a lower incidence of cancer, a lower risk of type 2 diabetes, a lower risk of developing Metabolic Syndrome (MetS), and a lower risk of all-cause mortality.¹ Lower Body Mass Index (BMI), blood sugar levels, systolic and diastolic blood pressure, levels of total and low-density lipoprotein cholesterol,  levels of triglycerides, levels of uric acid, and high-sensitivity C-reactive protein, and higher levels of plasma ascorbic acid observed in vegetarians are likely associated with these positive health outcomes.^1,2 

Dietary interventions involving vegetarian diets have shown improvements in participants' lipid profiles, including reductions in Triglycerides (TG), Low-Density Lipoprotein Cholesterol (LDL-C), and Total Cholesterol (TC). Patients with diabetes have been found to have decreased visceral fat, improved oxidative stress markers, and improved insulin sensitivity. While vegan diet-based interventions are uncommon, one experimental study found that a 3-week vegan dietary intervention reduced the level of inflammatory marker C-reactive protein (CRP). Participants in a further 4-week vegan dietary intervention used significantly less medication overall because their lipid levels and systolic and diastolic blood pressure were lower.¹

Despite these evaluations of protein quality, current guidelines for dietary protein intake do not specifically address protein quality. The Recommended Dietary Allowance (RDA) for protein is 0.80 g of “good quality protein” per kg of body weight per day (g/kg/day).¹ 

The acceptable macronutrient distribution range 

Developed by the Food and Nutrition Board of the Institute of Medicine (now the Health and Medicine division of the National Academies of Science), the Acceptable Macronutrient Distribution Range (AMDR) suggests a range of protein intake providing between 10–35% of daily calories in the diet.¹ The initial development of these recommendations was predicated on the minimum protein requirement, as established by nitrogen balance studies, for attaining body nitrogen equilibrium, or zero balance, in healthy adults. 

Higher protein intakes (1.2–1.6 g/kg/day) are suggested to optimize health above and beyond merely meeting the minimum requirements for the general population by implementing improved methodologies, such as the indicator amino acid oxidation technique.¹

Importance of adequate energy intake in plant-based diets

Energy intake is the most critical component of a diet, directly influencing overall health and performance. Insufficient energy intake can impair physical and cognitive performance, increasing the risk of illness and other health problems. Various factors affect energy needs, including age, gender, and body composition.²

For instance, children and adolescents require higher energy intakes to support growth and development, while adults need sufficient energy to maintain bodily functions and support daily activities. Additionally, energy requirements vary between people due to differences in muscle mass and metabolic rates. This means that your body composition also plays a significant role: individuals with higher muscle mass typically have higher energy needs than those with higher fat mass.^1,3 Energy intake must also be balanced with expenditure to maintain a healthy weight. This balance can be influenced by lifestyle factors such as physical activity levels, dietary habits, and metabolic health.² Athletes and those with active lifestyles need more energy to fuel their activities and support recovery, while sedentary individuals require less energy.

Plant-based diets can significantly influence energy supply due to their nutrient density and fibre content. Plant-based foods, such as fruits, vegetables, whole grains, legumes, nuts, and seeds, are typically lower in calories than animal products, making it easier to maintain a healthy weight. These foods provide essential nutrients and energy without the added saturated fats and cholesterol found in many animal products.³ Furthermore, plant-based diets can enhance energy levels by providing a steady release of glucose into the bloodstream, avoiding the energy spikes and crashes associated with high-sugar and high-fat diets. The high fibre content in plant-based foods also promotes satiety, helping to regulate appetite and prevent overeating.^2,3

The benefits of plant-based diets for health and the environment

Diets based mostly on plants have been linked to decreased mortality from ischemic heart disease and overall heart disease, which supports long-term weight management. This is why food intake must be balanced with expenditure to maintain a healthy weight. This balance can be influenced by lifestyle factors such as physical activity levels, dietary habits, and metabolic health. Athletes and those with active lifestyles need more energy to fuel their activities and support recovery, while sedentary individuals require less energy.² 

Dietary reforms at the population level are therefore essential for addressing the interconnected issues of diet, environmental sustainability, and public health. Vegetarian diets are often considered healthy choices. Producing animal-based foods, especially meat and dairy from ruminants, requires more resources and has a greater environmental impact compared to most plant-based foods.⁴ Plant-based diets have been associated with lower mortality rates from ischemic heart disease and overall heart disease. They support long-term weight management, reduce the need for medication, and decrease the risk of many chronic illnesses. These diets lower the prevalence and severity of high-risk conditions such as hypertension, obesity, hyperlipidemia, and hyperglycemia. Additionally, they have the potential to reverse advanced coronary artery disease and type 2 diabetes.^1,5

What should I eat?

Adopting a plant-based diet involves incorporating a variety of food groups to ensure balanced nutrition. Here are the recommended servings per day for each food group:⁵

Eliminating harmful ingredients in animal products

Adopting a plant-based diet offers the added benefit of eliminating or reducing the intake of harmful ingredients commonly found in animal products. This shift can lead to significant health improvements by reducing the presence of substances linked to various diseases. Key components to consider include:⁵

Saturated fats

The group of fatty acids known as saturated fats is mostly found in animal products but is also present in plants (mainly in tropical oils like coconut and palm) and has a well-established reputation in the literature for being linked to cardiovascular disease.¹ The American Heart Association reduced the amount of saturated fat that should be included in a heart-healthy diet to no more than 5% to 6% of total calories, which is the amount that is naturally present in a vegan diet.

Dietary cholesterol

The human body produces sufficient cholesterol for proper functioning. While dietary cholesterol's role in elevated serum cholesterol levels is debated, high intakes are linked to an increased risk of low-density lipoprotein oxidation, which promotes cardiovascular disease.

Antibiotics

A significant majority (70% to 80%) of antibiotics used in the US are administered to healthy livestock to prevent infections in the environments where these animals are housed. This practice is a leading cause of antibiotic-resistant infections, which resulted in 2 million illnesses and 23,000 deaths in Americans in 2013.

Insulin-like growth factor-1 (IGF-1)

Animals, including humans, naturally produce a hormone called insulin-like growth factor-1 (IGF-1), which promotes growth. Consuming animal proteins increases endogenous production of IGF-1, and an additional exogenous dose is absorbed. Promoting growth post-adulthood can enhance cancer proliferation.⁵

Summary

A plant-based diet offers a compelling approach to improving both personal health and environmental sustainability. This dietary choice emphasizes consuming predominantly plant-derived foods while minimizing or completely excluding animal products like meat, dairy, and eggs. Plant-based diets are rich in essential nutrients like fibre, vitamins, and minerals, crucial for overall well-being. By eliminating or reducing harmful components found in animal products, such as saturated fats, dietary cholesterol, antibiotics, and growth factors like insulin-like growth factor-1 (IGF-1), plant-based diets promote cardiovascular health and reduce the risk of antibiotic-resistant infections. Avoiding animal products furthermore improves lipid profiles, lowers blood pressure, enhances insulin sensitivity, and has potential weight management benefits. Beyond personal health benefits, adopting a plant-based diet contributes positively to environmental sustainability by reducing the environmental footprint associated with animal agriculture. Overall, transitioning to a plant-based diet supports your health and aligns with efforts to foster sustainable dietary practices for individuals and the planet.