The advice sounds reasonable: eat more plants, get your protein from legumes and grains, reduce your environmental footprint. I understand the appeal. I also understand what happens to a 40-year-old grappler who trains twice a day and tries to hit their protein target through lentils and pea protein. They lose muscle. They recover slowly. They get injured. Not because they're lazy — because the biology doesn't support the premise.
Not all protein is the same. The distinction isn't quantity — it's quality, measured through bioavailability, amino acid completeness, and leucine content. These three factors determine whether the protein you consume actually drives muscle protein synthesis and tissue repair — or passes through.
This post covers the specific mechanisms that make animal protein superior for midlife athletes under high training load — and the nutrient gaps that no plant-based diet addresses without serious supplementation.
Bioavailability: The Absorption Problem
Plant foods contain anti-nutritional factors — phytates, oxalates, lectins, and tannins — that bind to protein and minerals, reducing what the gut actually absorbs. The bioavailability of protein from legumes is approximately 50–70% versus 95%+ for animal protein. You're not absorbing what you think you're eating.
Phytates bind to zinc, iron, calcium, and magnesium in the gut — forming insoluble complexes that are excreted rather than absorbed. A diet centred on legumes and grains as protein sources is simultaneously a diet that impairs mineral absorption — creating deficiencies in the very micronutrients required for protein synthesis, testosterone production, and immune function.
Leucine is the rate-limiting amino acid for muscle protein synthesis. It acts as a molecular switch — triggering mTOR activation, which initiates the anabolic signalling cascade. Plant proteins are leucine-poor. To hit the leucine threshold (approximately 2.5–3g per meal) from lentils requires consuming roughly 500 calories of lentils. From beef: approximately 150 calories.
Muscle protein synthesis becomes less sensitive to dietary protein with age — a phenomenon called anabolic resistance. Overcoming it requires both higher total protein intake AND higher leucine concentration per meal. Plant protein fails on both counts relative to animal sources.
van Vliet S et al. (2015) — The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption. Journal of Nutrition.
The Missing Nutrients No Plant Food Provides
Vitamin B12 is found exclusively in animal foods. There is no plant source. Heme iron — the most bioavailable form — is found only in animal tissue. Retinol (true Vitamin A, not beta-carotene) is found only in animal liver and eggs. DHA (the omega-3 essential for brain function and inflammation management) is found pre-formed only in fatty fish and seafood.
The conversion efficiency of plant-based ALA to DHA is approximately 3–5% in healthy adults — lower in those under stress, with inflammation, or on restrictive diets. A plant-based athlete supplementing with flaxseed oil is not adequately replacing the DHA from salmon or sardines. The deficiency accumulates silently over years.
What Animal Protein Actually Provides
Beef, eggs, fish, and organ meats provide complete amino acid profiles, high leucine content, heme iron, zinc, B12, retinol, DHA, creatine, and carnosine — the full spectrum of nutrients required for high-frequency training adaptation in a single, bioavailable package.
- Minimum 1.6–2.2g protein per kg bodyweight daily for high-frequency grappling
- Prioritise leucine-dense sources: beef, eggs, fish, poultry per meal
- At least 3 meals per day exceeding the leucine threshold (approximately 30–40g animal protein per meal)
- Organ meats once per week minimum for micronutrient density
- Fatty fish 3–4x per week for DHA and EPA
After 40, anabolic resistance means you need more protein AND better protein. Plant sources fail on both counts.
— Josh Button · @thatjiujiteiroThe Bottom Line
This didn't come from a textbook or a coach handing me a protocol. It came from years of training hard, getting injured, burning out, and rebuilding — smarter every time. Everything in this post is something I do, have done, or have researched deeply enough to stake my performance on.
Start with one thing. Implement it fully. Then add the next. The compounding effect of doing the basics with precision beats any biohack or supplement stack.
Hard to Kill isn't a slogan. It's the standard.
Stay Dangerous. Stay on the Mats. Hard to Kill in Midlife.
