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Understanding Protein Intake: Recommendations, Sources, and Health Implications
Recommended Dietary Allowance (RDA) for Protein
The Recommended Dietary Allowance (RDA) for protein is a critical guideline for ensuring adequate protein intake. For healthy adults with minimal physical activity, the RDA is set at 0.8 grams of protein per kilogram of body weight per day . This recommendation is based on nitrogen balance studies, which assess the amount of protein needed to maintain a balance between nitrogen intake and loss. For older adults (65+ years), the recommended intake is slightly higher at 1.0 grams per kilogram of body weight per day to support metabolic and functional health.
Protein Intake Across Different Age Groups
Protein intake varies significantly across different age groups. In the United States, young children consume an average of 56 grams per day, while adults aged 19-30 years consume about 91 grams per day. This intake decreases to approximately 66 grams per day in the elderly. Despite these variations, the percentage of the population consuming less than the estimated average requirement is relatively low, with only 7.7% of adolescent females and 7.2-8.6% of older adult women falling below the recommended levels.
Health Benefits of Adequate Protein Intake
Adequate protein intake is essential for various physiological functions, including muscle protein synthesis, immune function, and overall physical health. Protein undernutrition can lead to severe health issues such as stunting, anemia, physical weakness, edema, vascular dysfunction, and impaired immunity. For individuals with varying levels of physical activity, higher protein intakes are recommended: 1.0 grams per kilogram for minimal activity, 1.3 grams for moderate activity, and 1.6 grams for intense physical activity.
Sources of Dietary Protein
Animal-Based Protein
Animal-based proteins, such as lean meat, milk, and fish, are considered high-quality proteins due to their complete amino acid profiles. These sources not only provide essential amino acids but also contribute significantly to the intake of other vital nutrients like calcium, vitamin D, and iron. However, excessive consumption of certain animal proteins, particularly processed meats, has been associated with higher risks of cardiovascular disease and all-cause mortality. Substituting these with healthier options like nuts, whole grains, legumes, and fish can lower these risks.
Plant-Based Protein
Plant proteins contribute approximately 32% of the protein intake in North America and are a significant part of the global diet. While plant proteins may have a different amino acid profile compared to animal proteins, mixtures of plant proteins can provide a complete and well-balanced source of amino acids. This makes them a viable option for meeting human physiological requirements.
Protein Supplementation and Health Outcomes
Protein supplementation, particularly in older adults, has shown promising results in improving lean tissue mass and overall nutritional status. For instance, a study found that protein supplementation at breakfast and lunch over 24 weeks led to a significant increase in lean tissue mass in healthy older adults. Similarly, protein-based nutritional supplements have been shown to decrease mortality and improve nutritional status in malnourished elderly patients during hospitalization and post-discharge.
Conclusion
Ensuring adequate protein intake is crucial for maintaining overall health and preventing various deficiencies and health issues. Both animal and plant-based proteins play essential roles in a balanced diet, and careful consideration of protein sources can help mitigate health risks associated with certain types of protein. By adhering to recommended dietary allowances and incorporating a variety of protein sources, individuals can support their physiological needs and promote long-term health.
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