# Proof: High-protein diets above 1.6 g/kg body weight damage kidneys in healthy people.

- **Generated:** 2026-03-31
- **Verdict:** DISPROVED
- **Audit trail:** [proof_audit.md](proof_audit.md) | [proof.py](proof.py)

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## Key Findings

- Three independent systematic reviews and meta-analyses — covering 28 RCTs with 1,358 participants plus a 148,051-person cohort meta-analysis — consistently find **no kidney damage** from high-protein diets in healthy adults (B1, B2, B3).
- A 2018 meta-analysis of 28 randomized controlled trials (the highest evidence level) concluded that higher-protein intakes **"do not adversely influence kidney function on GFR in healthy adults"** (B1).
- A 2024 meta-analysis of 148,051 participants found that higher protein intake is actually **associated with lower CKD risk**, not higher (B3).
- The 1.6 g/kg threshold in the claim is a sports-nutrition figure for muscle protein synthesis, not a clinically established kidney-safety limit; no nephrology guideline identifies it as a kidney-damage threshold for healthy people.

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## Claim Interpretation

**Natural language claim:** High-protein diets above 1.6 g/kg body weight damage kidneys in healthy people.

**Formal interpretation:** The claim is evaluated as: does high-protein intake (≥1.5–1.6 g/kg/day) cause measurable kidney damage — defined as adverse change in kidney function markers (GFR decline, increased proteinuria, or elevated creatinine) — in adults without pre-existing kidney disease?

**Proof direction:** Disproof. The sources in this proof **reject** the claim. Sources arguing in favor of the claim are documented in Counter-Evidence Search.

**Operator note:** The claim is DISPROVED if ≥3 independent systematic reviews or meta-analyses confirm that high-protein intake does NOT damage kidneys in healthy adults. The 1.6 g/kg threshold is not a clinically established kidney-safety boundary — it appears in sports nutrition literature (Morton et al. 2018) as an approximate upper limit for muscle protein synthesis optimization. The meta-analyses here study protein intakes ≥1.5 g/kg or "above the US RDA (0.8 g/kg)," both of which encompass the >1.6 g/kg range in the claim.

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## Evidence Summary

| ID | Fact | Verified |
|----|------|----------|
| B1 | Devries et al. (2018) Journal of Nutrition — meta-analysis of 28 RCTs, 1358 healthy adults: HP intakes do not adversely influence GFR | Yes |
| B2 | Van Elswyk et al. (2018) Advances in Nutrition — systematic review of RCTs and observational studies: higher protein consistent with normal kidney function | Yes |
| B3 | Cheng et al. (2024) Frontiers in Nutrition — meta-analysis of 6 cohort studies, 148,051 participants: higher protein associated with lower CKD risk | Yes |
| A1 | Verified source count (sources rejecting the claim) | Computed: 3 verified sources ≥ threshold of 3 |

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## Proof Logic

The claim asserts that protein intake above 1.6 g/kg/day causes kidney damage in otherwise healthy individuals. To disprove this, the proof requires ≥3 independently sourced systematic reviews or meta-analyses whose verified quotes confirm the claim is false.

**B1 — Devries et al. (2018), Journal of Nutrition.** This is the most direct evidence: a pre-registered systematic review and meta-analysis of 28 randomized controlled trials with 1,358 participants, explicitly restricted to adults without kidney disease. The RCTs compared high-protein intake (≥1.5 g/kg body weight, or ≥20% of energy, or ≥100 g/day) against normal- or lower-protein intake. The result: "Our analysis indicates that HP intakes do not adversely influence kidney function on GFR in healthy adults." While post-intervention GFR was slightly higher in the HP group (consistent with adaptive hyperfiltration), the *change* in GFR did not differ between groups — indicating no progressive kidney function loss.

**B2 — Van Elswyk et al. (2018), Advances in Nutrition.** An independent systematic review covering both RCTs and observational studies in healthy individuals consuming protein above the US RDA (0.8 g/kg). Conclusion: "These data further indicate that, at least in the short term, higher protein intake within the range of recommended intakes for protein is consistent with normal kidney function in healthy individuals." This review is independent of Devries et al. — different author team, different journal, different search protocol — providing a second line of evidence.

**B3 — Cheng et al. (2024), Frontiers in Nutrition.** The most recent meta-analysis: 6 prospective cohort studies totaling 148,051 participants with 8,746 CKD cases. Rather than finding harm, higher total, plant, and animal protein intake were each associated with *reduced* CKD incidence (total protein RR = 0.82, 95% CI 0.71–0.94). Conclusion: "The data showed a lower CKD risk significantly associated higher-level dietary total, plant or animal protein (especially for fish and seafood) intake." This further undermines the claim.

**A1 — Source count.** All three citations were verified live on their source pages (full quote match). Confirmed count: 3 ≥ threshold of 3. Claim holds (in the disproof direction), yielding verdict: **DISPROVED**.

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## Counter-Evidence Search

**1. Is there evidence that high-protein diets cause rapid kidney function decline in healthy adults?**

A search for "high protein diet rapid GFR decline healthy adults" identified Jhee et al. (2019, *Nephrology Dialysis Transplantation*), a Korean community-based prospective cohort of 9,226 healthy adults. The study reported that the highest protein intake quartile had 1.32× higher odds of rapid eGFR decline versus the lowest quartile. This is observational data, not a controlled experiment. Observational associations cannot establish causation — high animal protein consumption co-occurs with high sodium, red meat, and other dietary factors that independently affect kidney function. Crucially, the RCT meta-analysis (B1) — the highest level of evidence — found no adverse GFR change when protein was experimentally controlled. The observational association does not override the controlled trial evidence. Does not break the proof.

**2. Does glomerular hyperfiltration from high protein intake cause long-term kidney damage in healthy people?**

A search for "glomerular hyperfiltration high protein long-term damage healthy kidneys" identified Ko et al. (2020, *JASN*) and Kalantar-Zadeh et al. (2020, *Nephrology Dialysis Transplantation*). Ko et al. acknowledge the hyperfiltration mechanism and note "It is possible that long-term high protein intake may lead to de novo CKD" — but they also note that "long-term trials have not observed an increase in proteinuria" in those without kidney disease. Kalantar-Zadeh et al. argue for protein caution in vulnerable groups but explicitly state "persons with healthy intact kidneys may not be affected by this harmful impact." Adaptive hyperfiltration (transiently elevated GFR) is a normal physiological response to protein loading, not the same as kidney damage. No RCT has demonstrated histological damage or irreversible GFR decline in healthy adults from protein intake. Does not break the proof.

**3. Is 1.6 g/kg body weight a clinically established kidney safety limit?**

Searches for "1.6 g/kg protein kidney safety limit" and National Kidney Foundation/KDIGO guidelines found no support for this specific threshold as a nephrology safety cutoff. The 1.6 g/kg figure originates in Morton et al. (2018, *British Journal of Sports Medicine*) as an approximate upper bound for muscle protein synthesis optimization, not a kidney-safety boundary. Clinical nephrology guidelines address protein restriction for people *with* CKD; they set no upper-limit threshold for healthy adults. Does not break the proof.

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## Conclusion

**Verdict: DISPROVED**

Three independently verified systematic reviews and meta-analyses (B1, B2, B3) — totaling randomized controlled trial data from 1,358 healthy participants and prospective cohort data from 148,051 participants — consistently find that high-protein diets do not damage kidneys in healthy individuals. The most direct evidence (B1) comes from 28 RCTs specifically measuring GFR changes in adults without kidney disease; GFR changes did not differ between high-protein and normal-protein groups.

The claim confuses two distinct populations: people *with pre-existing kidney disease* (for whom protein restriction is clinically indicated) and people *with healthy kidneys* (for whom high protein is not shown to cause damage). The 1.6 g/kg threshold in the claim is not a nephrology safety limit; it is a sports-nutrition figure. No clinical guideline identifies it as a kidney-damage threshold for healthy adults.

All three citations were fully verified on their source pages. No adversarial check broke the proof.

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*Generated by [proof-engine](https://github.com/yaniv-golan/proof-engine) v1.3.1 on 2026-03-31.*
