The 5 most important protein questions answered with the latest science | Dr Matthew Nagra

What It Covers

Dr. Matthew Nagra and Simon Hill examine protein science, revealing optimal intake ranges of 1.2-1.6 grams per kilogram for muscle building, no superiority of animal over plant protein for strength gains, and significant chronic disease risk reduction when swapping animal for plant protein sources.

Key Questions Answered

• •Optimal Protein Intake: Research shows 1.6 grams per kilogram represents the plateau for muscle and strength gains when paired with resistance training. Most benefits occur at 1.2 grams per kilogram, with minimal additional gains beyond this. Recommendations of 2+ grams per kilogram lack scientific support even in energy-restricted states or elderly populations.
• •Plant vs Animal Protein for Muscle: Clinical trials from Brazil and UK show no significant differences in muscle mass or strength gains between vegan and omnivorous diets when protein intake matches at 1.6-1.8 grams per kilogram. Daily muscle protein synthesis studies in 72-year-olds at 1.2 grams per kilogram confirm equal anabolic effects regardless of protein source.
• •Chronic Disease Risk Reduction: Substituting just 3% of calories from animal protein to plant protein (approximately 15 grams daily) associates with 38% greater odds of healthy aging, 41% reduced physical function limitations, and 28% lower cardiovascular disease risk in high-protein diets. Plant protein outperforms all other macronutrients in substitution analyses across multiple health outcomes.
• •IGF-1 Concerns Overstated: Protein interventions increase IGF-1 by only 0.4 nanograms per milliliter on average, while Mendelian randomization studies show cancer risk increases require 44 nanograms per milliliter elevation. Even milk protein, which produces the highest spike at 13.8 nanograms per milliliter, remains well below concerning thresholds for cancer promotion.
• •Planetary Health Alignment: Plant protein production requires 50-100 times less land and produces approximately 30 times fewer greenhouse gas emissions per gram of protein compared to beef. The EAT-Lancet planetary health diet achieves 1.2-1.3 grams protein per kilogram while meeting all micronutrient needs and reducing environmental impact by 75% in land use.