Protein, Kidneys, and Longevity: Should You Really Worry About Eating Too Much?

Protein Restriction and Longevity: What the Research Really Says

Protein and Bone Health

We already know there’s a generally positive association between protein intake and bone mineral density (BMD); the more protein you eat, the better your BMD tends to be, especially when calcium intake is adequate. That’s clear from several large population studies and systematic reviews.

But the conversation gets messy when people start worrying about cancer, kidney health, or IGF-1. Influencers like Brian Johnson and David Sinclair often argue for keeping protein low to reduce IGF-1. It’s confusing, especially for those with osteoporosis or declining bone density.

So let’s cut through the noise and look at what the research actually shows about protein, kidneys, and longevity.

The Nurses’ Health Study: Protein and Healthy Aging

A 2024 study using data from the long-running Nurses’ Health Study followed nearly 49,000 women (mean age <60 in 1984) for about 30 years.

Definition of healthy aging: free from 11 major chronic diseases (including kidney disease), no cognitive or physical impairment, and good mental health.

‍

Findings:

• Higher total protein intake was significantly associated with better odds of healthy aging.
  
  
• Plant protein showed the strongest association—but, as researchers noted, this may partly reflect healthy-user bias, since plant-focused eaters often engage in other health-promoting habits.
  
  
• Most importantly, there was no link between higher protein intake and kidney disease in this large cohort.

‍

Protein and Kidney Disease Risk

A 2024 meta-analysis involving over 150,000 participants found something surprising:

• Higher total, animal, and plant protein intake was associated with a lower risk of developing chronic kidney disease (CKD).
  
  
• Differences seen across subgroups likely reflected overall diet quality, not the protein itself.
  
  

Takeaway: In healthy individuals, protein does not cause CKD, and higher intake may actually be protective. The only time restrictionthat  matters is in those with existing, advanced kidney disease.

Protein Intake and Mortality

You’ve probably heard that high-protein diets shorten lifespan. But a 2022 analysis of the NHANES database challenges that idea.

• Low protein diets (<0.8 g/kg) were not protective against death.
  
  
• Kidney function, not protein intake, predicted mortality.
  
  
• In healthy adults, protein intake wasn’t associated with a higher risk of death from cancer, kidney disease, or any other cause.
  
  

Meta-analyses of RCTs back this up: in healthy adults, higher-protein diets do not harm kidney function or shorten lifespan.

‍

When Protein Restriction Might Matter

Protein restriction guidelines mainly apply to advanced CKD, not healthy people.

• KDOQI Guidelines (2020, U.S.): 0.55–0.60 g/kg for CKD stages 3–5.
  
  
• UK Guidelines: more liberal, 0.8–1.0 g/kg even in later CKD stages.
  
  

Evidence is limited, and strict restriction often worsens nutrition quality or leads to excessive carbohydrate intake. Some studies show mild benefit in stage 4–5 CKD, but results are mixed and highly individual.

As Dr. Doug says: “If you have healthy kidneys, we don’t need to worry about protein intake. Restriction really only comes into play in severe kidney disease.”

Understanding Kidney Function Tests

Many people believe they have kidney disease when they don’t. Here’s why:

• eGFR (estimated glomerular filtration rate) is just a screening tool, not a definitive diagnosis.
  
  
• A CKD diagnosis requires both:
  
  
  
  • Evidence of kidney damage in the urine (e.g., protein or albumin)
    
    
  • Persistently low eGFR (<60) for at least 3 months
    
    

A single low eGFR reading does not mean you have CKD.

‍

The Big Picture: Protein, Longevity, and Bone Health

For people with normal kidney function, the data show:

• Higher protein intake supports healthier aging and muscle preservation.
  
  
• Protein does not cause kidney disease.
  
  
• Protein does not shorten lifespan.
  
  
• Protein is essential for maintaining both muscle and bone mass.
  
  

For people with advanced CKD, protein restriction may still have a role—but this is highly individualized and should always be guided by a nephrologist.

Why This Matters for Osteoporosis

If you have osteoporosis or osteopenia, protein isn’t optional.

• Low protein intake leads to muscle loss (sarcopenia) and worsens bone density decline.
  
  
• Without adequate protein, your body lacks the building blocks to rebuild bone.
  
  
• Protein restriction may actually reduce healthspan by raising fracture risk and functional decline.
  
  

As Dr. Doug says, “You won’t live longer if you avoid protein, you’ll lose muscle, develop osteoporosis, and increase fracture risk. That has a real impact on both lifespan and healthspan.”

Final Thoughts

High-protein (or “optimal-protein”) diets are not harmful for healthy kidneys. They’re actually protective for bone, muscle, and long-term vitality.

If you have CKD, work closely with your doctor to set the right protein target. However, if your kidneys are healthy, stop worrying; adequate protein supports both health span and lifespan.

👉 If you’re still unsure how much protein is right for you, or how to balance bone health with longevity, join me in our free OsteoCollective masterclass. I’ll walk you through the myths and misconceptions, and you’ll have a chance to ask your questions live during the Q&A.