The FAO Committee on World Food Security defines healthy diets as “those that include an appropriate balance of the foods necessary to achieve the optimal growth and development of all individuals and to meet their physiological needs and support their physical, mental and social wellbeing at all life stages. Healthy diets are safe, diverse, balanced and based on nutritious foods. They help to protect against malnutrition in all its forms, including undernutrition, micronutrient deficiencies, overweight and obesity, and lower the risk of diet-related non-communicable diseases”.  FAO

Nutrient deficiencies refer to more than just total nutrients supplied by a diet. Deficiencies occur because the balance of essential nutrients required for health has not been adequate, and shortchanging the body on just one nutrient can impact health, even if there is an over-abundance of others.

Diets lacking balance or nutritional adequacy can lead to stunting, emaciation and starvation at one extreme or to obesity at the other, and both ends of the spectrum result in extreme health problems.

A healthy diet is of particular importance to pregnant and lactating women, children and the elderly, all of whom are most at risk of severe and lasting consequences from poor nutrition

High quality diets reflect human evolution, with a broad mix of complementary foods of both animal and plant origin.

Proteins, carbohydrates and fats are macronutrients that can be obtained from all diet types, however their form, bioavailability and relative proportions impact health outcomes. Proteins are of particular importance and are composed of amino acids, all of which can be found in animal-source foods. However, few plant-based foods provide the full complement of amino acids required for human health. While supplementation can be used to balance some vegan and vegetarian diets, it is extremely difficult to achieve a well-balanced diet for the most at-risk population groups.

Animal-sourced foods are high quality nutrient dense foods that contain all the essential amino acids, a high proportion of protein relative to calories, and are substantial sources of vital micronutrients including iron, zinc, calcium and vitamins including vitamin B12, in highly bioavailable and bio-accessible natural forms.

The Food and Agriculture Organization of the United Nations estimates that 843 million people worldwide are hungry, and a greater number suffer from nutrient deficiencies. Approximately one billion people have inadequate protein intake.

Researchers and nutrition experts can assess global trends in dietary quality by estimating the micronutrient density of the food supply in a region or country, including the prevalence of inadequate intake of 14 micronutrients. This kind of analysis shows that animal-source foods are essential components of balanced healthy diets and of extreme importance for the health and wellbeing of at-risk groups including children and pregnant and lactating women.
Plant-based vegan or vegetarian  diets require supplementation to meet nutritional needs, which is difficult enough in high income societies and often impossible in lower income developing countries.

Beyond protein, meat offers a variety of nutrients that are difficult to replace with plant-based alternatives. These include long-chain omega 3 fatty acids, retinol (vitamin A), and minerals like iron and zinc in bioavailable forms. Global diets already suffer from deficiencies in some of these nutrients, making it crucial to consider physiological needs when adopting meat-free diets.

Though meat makes up less than 10% of global food mass and energy intake, its nutritional impact is profound. It provides the majority of the world's vitamin B12, along with other key vitamins and bioactive compounds like taurine, creatine, and carnosine, which contribute to overall health.

Meat is also more than the sum of its parts—it plays a unique role within the broader food system, particularly in regions where diets are dominated by cereals. Reducing meat intake too drastically, especially for populations already at risk of undernutrition, could have serious consequences. This is not only an issue in developing countries but also in certain high-income regions where meat consumption is already low, potentially affecting physical and cognitive development and economic progress.