Protein

Why protein matters more than most people think

Protein is the most underrated macronutrient in the average diet. It isn't just for bodybuilders. Every enzyme, hormone, antibody, and structural tissue in your body is built from protein. Your immune system runs on it. Your bones depend on it. And as you age, getting enough becomes one of the single most effective things you can do to stay functional and independent. A 2022 meta-analysis found that protein intake below 0.8 g/kg/day significantly increases sarcopenia risk, the progressive loss of muscle mass and strength that accelerates after 50 ^[1].

The official RDA of 0.8 g/kg body weight was designed to prevent deficiency in sedentary adults. It was never meant to optimize health. Current evidence from exercise science and gerontology supports considerably higher intakes, particularly for anyone who exercises regularly or is over 65 ^[2].

The leucine threshold: why protein quality matters

Not all protein is equal when it comes to triggering muscle repair. Muscle protein synthesis (MPS) is switched on primarily by two things: resistance training and the amino acid leucine. You need roughly 2.5-3 grams of leucine per meal to activate the mTOR pathway, which is the master switch for building new muscle tissue ^[3]. That translates to about 25-30 grams of high-quality protein per sitting.

This is where source matters. Whey protein contains about 11% leucine, eggs about 8.5%, and chicken about 7.5%. Most plant proteins fall below 7%, which means you need a larger serving to hit the threshold. Older adults face an additional challenge: anabolic resistance, a blunted MPS response that means they may need close to double the protein per meal compared to someone in their twenties to get the same muscle-building signal ^[4]. That's why researchers now recommend at least 30-40 grams of protein per meal for people over 65.

How much protein do you actually need?

For physically active adults, the evidence points to 1.6-2.2 g/kg of body weight per day, distributed across 3-4 meals ^[2]. For older adults with moderate activity, 1.2-1.6 g/kg is a reasonable minimum. A 2024 study on older women with sarcopenia found that 1.2 g/kg/day led to measurable improvements in muscle strength and body composition compared to the standard 0.8 g/kg recommendation ^[5].

Distribution matters nearly as much as total intake. Research shows that 24-hour muscle protein synthesis is about 25% higher when protein is spread evenly across meals rather than loaded into dinner ^[6]. The practical target: 30-50 grams of quality protein at breakfast, lunch, and dinner, with an optional pre-sleep serving of casein-rich food like Greek yogurt to sustain overnight MPS.

Plant protein vs. animal protein

A 2025 systematic review comparing plant and animal proteins found that 75% of direct comparison studies showed no significant difference in muscle protein synthesis when total protein and leucine were matched ^[7]. So plant-based diets can absolutely support muscle maintenance, but they require more planning. The DIAAS (Digestible Indispensable Amino Acid Score) ranks whole eggs, milk proteins, and beef highest, with most isolated plant proteins scoring below 75 ^[8]. Combining rice and pea protein, for example, creates a complete amino acid profile comparable to whey.

Interestingly, the picture shifts when we look at longevity rather than just muscle. The Nurses' Health Study, following 48,762 women from midlife, found that plant protein was associated with 46% higher odds of healthy aging (defined as freedom from chronic disease, good cognition, and intact physical function), while animal protein was associated with 6% lower odds ^[9]. This doesn't mean animal protein is harmful, but it suggests that a mix of sources, with generous plant protein intake, may be the best strategy for long-term health.

Protein and kidney health: the myth that won't die

The idea that high protein intake damages healthy kidneys has been repeated for decades, but the data doesn't support it. A 2024 meta-analysis of 148,051 participants found that higher protein intake from both plant and animal sources was actually associated with decreased chronic kidney disease incidence in healthy people ^[10]. Intakes of 1.6-2.2 g/kg show no adverse kidney effects in people without pre-existing renal disease. If you do have kidney disease, that's a different conversation, but healthy adults don't need to worry.

Practical protein strategies

• Aim for 1.6-2.2 g/kg body weight daily if you train regularly, spread across 3-4 meals of at least 30g each
• Prioritize leucine-rich sources: whey, eggs, chicken, fish, beef, Greek yogurt, cottage cheese
• Eat 30-50g protein within 2 hours after resistance training
• Consider a pre-sleep casein source (Greek yogurt, casein shake) for overnight muscle repair
• For plant-based diets, combine complementary proteins and consider adding 3g leucine per meal
• Track your intake for a week or two. Most people overestimate how much protein they eat