The important role of animal-sourced foods in a healthy diet across the lifespan

Among many nutrient-dense foods, animal-sourced foods (ASF) stand out for their nutrient density, from high-quality protein content to many key vitamins and minerals, thus offering a convenient and efficient way to obtain a wide range of essential nutrients.

To further explore the importance of ASFs and protein quality within a healthy diet, a 2024 study examined their role across different population groups including children, adults, and older adults.¹ They also address how ongoing research challenges the common beliefs about the health risks associated with ASFs, alongside supporting evidence from the 2020-2025 Dietary Guidelines for Americans.

Understanding Protein Quality

Animal-sourced proteins are considered high-quality as they contain the right proportions of essential (indispensable) amino acids, which the body cannot synthesize. In contrast, plant-sourced proteins often fall short in one or more of these amino acid building blocks, limiting protein synthesis.

Additionally, protein digestibility impacts the biological availability of amino acids, often measured by the Digestible Indispensable Amino Acid Score (DIAAS). This score reflects the concentration of indispensable amino acids per gram of protein, adjusted for digestibility at the end of the small intestine, and is determined by the most limiting essential amino acid.

The Nutrient Contributions of ASFs

While being a source of high-quality protein, ASFs are also important contributors of essential nutrients including zinc, iron, vitamin B12, selenium and phosphorus, which are often lacking or absent in plant-sourced foods. Moreover, the bioavailability of iron, zinc, vitamin A, and vitamin D is notably higher in ASFs compared to many plant-sourced foods. ASFs also have an enhancing effect on iron and zinc absorption from plant-sourced foods, further contributing to meeting daily nutrient needs.

The high nutrient density of ASFs enhances their caloric efficiency, allowing them to provide essential nutrients effectively without adding excessive calories. For example the study highlights that, assuming a 2,000kcal diet, 3 cups of low-fat milk a day, as recommended by the 2020-2025 Dietary Guidelines for Americans (DGA), contributes 100% of calcium and phosphorus, 50% of protein, and a significant portion of potassium, magnesium, riboflavin needs for adults, alongside other micronutrients. Similarly, to match the zinc content in 100g of cooked lean beef, which also contributes protein, niacin, selenium, and vitamin B12, one would have to consume 15 tbsp of peanut butter, which contributes 7.5 times more calories.

The Role of ASFs Across Different Age Groups

Infants and Children

Infants and children face the challenge of adequately meeting nutritional needs to support optimal growth, while having a decreased ability to consume foods in large quantities. Thus, the nutrient density of ASFs make them key in the prevention of nutrient deficiencies and the promotion of optimal growth and development. As stated by the World Health Organization (WHO), “ASFs are the best source of high-quality nutrients to reduce stunting in toddlers and young children.”²

Increasing research supports the role of ASFs in the prevention of childhood obesity, with one study demonstrating that the consumption of cow’s milk is associated with increased lean mass, decreased body fat, and increased overall protein balance, in conjunction with increased childhood height. Given that childhood obesity is a strong predictor of adult obesity and increases the risk of developing chronic diseases such as cardiovascular diseases, diabetes, osteoarthritis, and cancer later in life, early intervention is important. Additionally, seeing as malnutrition is a pervasive health issue worldwide with about 21% (144 million) of children under 5 years old being stunted and 7% (47 million) being wasted, ASFs can play an important role in improving nutrient deficiencies and mitigating adverse consequences. These include improved cognitive development and function and greater length-for-age.

Adults

Since 1990, there has been an eminent surge in obesity rates worldwide, having doubled over the years. Protein-rich foods can play a role in weight management. In fact, a meta-analysis found that increasing protein intake from 15% to 30% of total calories - by replacing carbohydrates - promoted weight loss while preserving lean body mass. ASFs also promote satiety, which can support higher diet quality. Additionally, ASFs have been shown to provide beneficial effects on muscle anabolism when coupled with resistance exercise. Additionally, this review notes that the timing of protein intake is also important; consuming 30g of high-quality proteins 3 times a day may stimulate muscle protein synthesis more compared to a skewed protein consumption pattern.

Older Adults

With increasing age, protein requirements also increase to support muscle mass preservation, disease recovery, maintenance of physical autonomy, and protection against inflammatory and catabolic conditions, frailty, and falls. This increase in protein needs is primarily due to age-related anabolic resistance, which ultimately hinders muscle protein synthesis and leads to muscle loss. A prospective cohort study has found that increased consumption of ASFs over a 20-year period was associated with preservation of muscle mass and functional performance among older adults.

Challenging Health Assumptions Associated with ASFs

The saturated fat in ASFs, particularly red meats, has often been criticized for its presumed negative health effects. However, emerging research suggests the need for re-evaluation, in the scope of the whole food matrix, especially with unprocessed meats and whole-fat dairy.

The 2020-2025 Dietary Guidelines for Americans

The United States Department of Human and Health Services (HHS) and the United States Department of Agriculture (USDA) published the 2020-2025 Dietary Guidelines for Americans (DGA) to promote healthy eating with key recommendations to “make every bite count”.

In recognition of the nutrient-dense nature of ASFs, the DGA recommends the daily consumption of 3 cups of dairy and 150g of lean meats, poultry, eggs, or seafood within a 2,000kcal diet.

For infants and toddlers, the DGA recommends incorporating animal-source proteins, along with nuts, seeds, and soy products, as complementary foods, given their rich protein, iron, zinc, choline, and long-chain polyunsaturated fatty acids contents. By age 2, dairy and fortified soy products are recommended, for their calcium contribution, along with vitamin D fortified cow’s milk or soy beverages. Plant-based products (except soy products) are significantly lower in protein and do not naturally contain calcium.