🥩🌱 Does Protein Cause Cancer? Not So Fast — What the Latest Research Really Says

September 2025

In the age of viral headlines and fear-based nutrition advice, one common myth just won’t die: “High protein diets, especially animal protein, cause cancer.” 

Often, this claim is linked to mTOR activation — a cellular growth pathway said to promote aging and cancer if overstimulated. But is that really what the science shows?

A new 2025 study published in Applied Physiology, Nutrition, and Metabolism says otherwise — and it’s not alone.

📊 The Study: What They Did and Why It Matters

🧪 Study Design & Methods

Researchers Yanni Papanikolaou, Stuart Phillips, and Victor Fulgoni analyzed data from NHANES III, a large, nationally representative U.S. health survey conducted between 1988 and 1994, with follow-up mortality data extending up to 2015.

• Participants: 10,721 adults (age ≥19 years)

• Dietary Assessment: Single 24-hour dietary recall to estimate usual intake of:

  • Total protein

  • Animal protein

  • Plant protein

• Outcome Measures:

  • All-cause mortality

  • Cardiovascular disease mortality

  • Cancer-related mortality

• Statistical Adjustment: Controlled for age, BMI, smoking, alcohol, energy intake, physical activity, and more.

🧬 Findings

🟢 No increased mortality risk was observed for any type of protein—animal, plant, or total.

🟢 Even individuals in the highest quartile of animal protein intake did not show a higher risk of dying from cancer, heart disease, or any cause.

These findings directly challenge the notion that typical protein intake levels — including from animal sources — pose a danger to longevity or increase cancer risk.

🔍 Where This Fits in the Big Picture

This new paper isn’t a lone voice — it joins a growing body of research showing protein adequacy, not avoidance, is key to healthy aging:

• Morton et al. (2018): Protein supplementation improves muscle mass and strength with resistance training in adults.

• Ten Haaf et al. (2022): Even in non-frail older adults, protein improves lean body mass and function.

• Layman et al.: Emphasize the importance of protein quality and leucine threshold for muscle maintenance, especially with age.

🧠 Let’s Talk About mTOR: Growth ≠ Cancer

Much of the fear around protein and cancer stems from a misunderstanding of mTOR (mechanistic Target of Rapamycin) — a nutrient-sensing pathway that regulates growth, repair, and metabolism.

Yes, overactivation of mTOR in the wrong context (e.g. cancer cells) can contribute to disease progression.

But in healthy individuals, periodic activation of mTOR — especially in muscle tissue following protein intake or resistance training — is essential for maintenance, repair, and healthy aging. Shutting it down indiscriminately may actually worsen sarcopenia, frailty, and immune decline.

🧬 The key lies not in “avoiding mTOR,” but balancing activation with recovery — much like exercise itself.

🛡️ Bottom Line: Protein Doesn’t Deserve the Blame

Here’s what this 2025 study (and many before it) make clear:

• Eating adequate protein, even from animal sources, is not associated with higher risk of dying from cancer or heart disease.

• Protein helps preserve muscle mass, immune function, and metabolic resilience — especially critical in aging.

• mTOR activation is not inherently dangerous — it’s a normal, adaptive, and necessary physiological process.

🥦🥩 Final Thoughts: Flexibility Over Fear

Instead of demonizing protein, we should be asking:

• Are we getting enough high-quality protein, especially as we age?

• Are we pairing it with strength training to maintain function?

• Are we spreading protein across meals to support anabolism throughout the day?

Whether you're an omnivore, vegetarian, or flexitarian, the science supports protein adequacy and diversity — not restriction based on myths.

🔗 Full citation:

Papanikolaou, Y., Phillips, S. M., & Fulgoni, V. L. III. (2025). Animal and plant protein usual intakes are not adversely associated with all-cause, cardiovascular disease–, or cancer-related mortality risk: An NHANES III analysis. Applied Physiology, Nutrition, and Metabolism. https://doi.org/10.1139/apnm-2023-0594

#Protein Intake, #Cancer Risk, #mTOR Pathway, #Healthy Aging, #Nutrition Myths