Why Protein Matters More Than Ever After 70

This is called anabolic resistance, and understanding it is critical to maintaining muscle, strength, and independence in advanced age.

Anabolic resistance is real

Anabolic resistance is the decreased ability of muscle tissue to respond to the anabolic signal of dietary amino acids and resistance exercise.¹ It's not that your muscles can't build protein. It's that they're less responsive to the signals that trigger protein synthesis.

This happens for several reasons. Mitochondrial function declines with age. Cellular signalling becomes less efficient. Insulin sensitivity decreases. The hormonal environment becomes less anabolic. All of these factors combine to create muscle tissue that's resistant to growth signals.

The consequence is that an older adult needs considerably more protein stimulation to achieve the same degree of muscle protein synthesis as a younger adult. What this means practically is that you can't eat the way you did at 40 and expect the same result.

A younger person might build muscle on 20 grams of protein at a meal. By your 70s, you might need 40 to 50 grams to trigger a similar response. The threshold has literally doubled or more.

Anabolic resistance means your muscles have become less responsive to protein. This isn't optional to address. It's the primary driver of sarcopenia. Feed the resistance.

Why elderly need more protein

This is where recommendations diverge from reality. Official dietary recommendations are still based on earlier science that didn't account for anabolic resistance. They suggest 0.8 grams of protein per kilogramme of body weight daily.

For someone over 70 trying to maintain muscle, this is woefully inadequate. Research shows that older adults maintaining muscle require between 1.2 and 2 grams per kilogramme daily, depending on activity level and how much muscle loss they're already experiencing.²

This isn't to pack on muscle. This is just to maintain what you have. Muscle is metabolically expensive to maintain. Your body would prefer to lose it and reduce the energy cost. Without adequate protein and stimulus to keep it, muscle is shed.

The higher protein intake serves multiple purposes. First, it provides the amino acids your muscles need to maintain protein synthesis despite anabolic resistance. Second, it provides amino acids for other functions including immune function, neurotransmitter synthesis, and hormonal balance. Third, higher protein intake is associated with improved satiety, so you eat more healthily overall.

Leucine is the critical trigger

Not all amino acids are equal. Leucine is the critical amino acid for triggering muscle protein synthesis. It's the one that signals the mTOR pathway, the primary driver of muscle protein synthesis.³

In younger people, roughly 20 to 25 grams of mixed protein provides enough leucine to trigger muscle protein synthesis.³ In older people, particularly those with significant anabolic resistance, 40 to 50 grams might be needed to get the same leucine threshold and the same protein synthesis response.

This is why spreading protein throughout the day matters. Three meals of 40 to 50 grams of protein each provides multiple opportunities to trigger muscle protein synthesis. A pattern of low protein at breakfast, low at lunch, and high at dinner doesn't work. You miss multiple opportunities throughout the day.

Leucine is found in all animal proteins. Beef, fish, eggs, and dairy all contain it. Plant proteins have less leucine per unit of protein, which is one reason why plant-based protein is less effective for maintaining muscle in older adults.

This doesn't mean you need to eat only animal protein. It means that animal proteins should be the foundation, with complementary plant foods providing fibre and other nutrients.

Complete amino acids matter

Complete amino acids means all nine essential amino acids in adequate ratios. Animal proteins are complete. Plant proteins are almost all incomplete, lacking one or more essential amino acids.

This matters for muscle protein synthesis. If the amino acid profile is incomplete, your body can't synthesise muscle protein at full efficiency. It's like trying to build a wall when you're missing certain types of bricks. Some amino acids are abundant, others are limiting.

Combining plant proteins to create a complete amino acid profile is possible (rice and beans, for example), but it requires knowledge and planning. Eating animal proteins provides complete amino acids automatically, with no planning required.

This is why, for people over 70 focused on muscle maintenance, animal proteins should form the foundation. They're complete, they're high in leucine, they're more bioavailable, and they provide multiple nutrients beyond just amino acids.