Optimal Protein Sources
Protein is an essential macronutrient that plays a crucial role in building and repairing tissues, making enzymes and hormones, and supporting overall health. With a wide variety of protein sources available from both animal and plant-based foods, it’s important to understand which options are the most optimal for meeting your daily protein needs while promoting long-term health and well-being.
Comparing Animal and Plant-Based Protein Quality
Animal proteins are considered complete proteins as they contain all nine essential amino acids, while plant proteins are often incomplete, lacking one or more essential amino acids. However, consuming a variety of plant proteins can provide all essential amino acids. Animal proteins generally have higher digestibility and bioavailability compared to plant proteins, with higher Protein Digestibility Corrected Amino Acid (PDCAA) scores. For example, milk, whey, egg, casein and beef have the highest PDCAA score of 1.0, while soy scores 0.91, pea 0.67, oat 0.57, and whole wheat 0.45.Meta-analyses have shown that animal protein tends to support greater gains in lean mass and percent lean mass compared to plant protein, especially in younger adults under 50 years old. However, protein source did not significantly affect changes in muscle strength. While animal proteins are often superior in terms of amino acid profile and digestibility, plant proteins can still support muscle growth when consumed in sufficient amounts and variety.
The Role of Protein in Muscle Preservation
Protein plays a vital role in preserving lean muscle mass, especially as we age. Consuming adequate protein stimulates muscle protein synthesis, helping to repair and rebuild muscle tissue. Among the essential amino acids, leucine is particularly important for activating the mTORC1 pathway, which initiates protein synthesis and promotes muscle growth. Studies have shown that consuming protein rich in essential amino acids, particularly leucine, can enhance muscle protein synthesis and lead to greater gains in lean mass, even in older adults.Distributing protein intake evenly throughout the day may further optimize muscle preservation. During weight loss, a higher protein intake of 1.5 g/kg/day can help prevent the loss of lean mass when combined with resistance exercise. Both animal and plant proteins can contribute to muscle preservation, although animal proteins tend to be more easily digestible and have a more complete amino acid profile. Ultimately, consuming sufficient protein from a variety of sources, in combination with regular physical activity, is key for maintaining healthy muscle mass and strength throughout life.
Increased Protein Needs with Aging
As we age, our protein requirements increase to help maintain muscle mass, strength, and function. Older adults are less responsive to the anabolic stimulus of low doses of amino acid intake compared to younger individuals, a phenomenon known as anabolic resistance. However, this lack of responsiveness can be overcome with higher levels of protein consumption, particularly from high-quality sources rich in essential amino acids.Experts recommend a protein intake between 1.2 and 2.0 g/kg/day or higher for elderly adults, which is well above the current RDA of 0.8 g/kg/day. Consuming protein at the upper end of the Acceptable Macronutrient Distribution Range (AMDR), as much as 30-35% of total caloric intake, may prove beneficial for maintaining muscle health in older adults. Spreading protein intake evenly throughout the day, with 25-30 grams of high-quality protein per meal, can help optimize muscle protein synthesis and counteract age-related muscle loss.