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🧬 Protein flipped twice this year.
US guidance rose to 1.2–1.6 g/kg — close to double. Then on 31 July, a Cell Press Blue review of 350+ papers concluded most people already eat more than they need. My patients spent the week asking the same question: more, or less? 🤔
My answer: both are right. What’s wrong is expecting one number to fit everyone.
⚠️ Age 65 is a hinge — the mortality association reverses direction across it
🩺 CKD ceiling is 1.3 — the entire new US band clears it
🔁 Dialysis runs the other way — these patients need more protein, not less
🏋️ Without resistance training, arguing about grams is beside the point
The line I’d most want to survive the piece: 🔍 test first, then talk about eating.
Taiwan’s CKD prevalence sits near 11.9% with awareness around 3.5%. For every hundred people with impaired kidney function, three or four know it. The rest are adjusting their diets on guesswork — in whichever direction.
Full piece 👇
Longevity Nutrition · Evidence Review
Protein Flipped Twice This Year — So Who Should You Listen To?
US guidance nearly doubled. Then a 350-paper review said most of us already eat too much. As a nephrologist, I’d argue the conflict isn’t in the data — it’s in expecting one number to fit everyone.
- The new review is about sedentary populations eating above their needs — not a blanket instruction to eat less.
- Age 65 is a hinge. The mortality association reverses direction across it.
- For chronic kidney disease, the ceiling is 1.3 g/kg — the entire new US band clears it.
- Dialysis patients run the opposite way: they need more protein, not less.
- Without resistance training, arguing about grams is beside the point.
Earlier this year, US dietary guidance raised the daily protein target to 1.2–1.6 grams per kilogram of body weight — close to double the previous figure. Then on 31 July, Cell Press Blue published a review drawing on more than 350 papers, concluding that most people already consume more protein than they actually need.
Two signals, opposite directions, same year. My clinic patients have been asking me the same question all week: so do I eat more, or less?
What the review actually says
Pulling together decades of work, the review argues that restricting protein may slow aging through several converging routes: better metabolic control, altered nutrient-sensing responses inside cells, less cellular damage, and better maintenance of cellular function.
The central player is a hormone called FGF21. When protein intake falls, FGF21 rises — increasing energy expenditure, improving glucose control, and reducing inflammation. Animal work shows mice with higher FGF21 live longer, and the effect is more pronounced in males than females.
The review also singles out three amino acids — methionine, isoleucine and valine — as the drivers behind these effects. Consumed in excess, they can switch on growth-promoting signalling associated with obesity, inflammation and other age-related disease.
But the part worth reading twice is what the author adds himself.
He is explicit that protein’s benefits for muscle growth and exercise response in physically active people are not in doubt. The problem, as he frames it, is that most people are relatively sedentary. He also notes that athletes consume large amounts of protein without developing metabolic disease, and suspects regular exercise is what protects them. And he flags that pregnant women and some older adults need more protein, not less.
His conclusion isn’t “everyone should eat less.”
It’s “recommendations need to be personalised — by age, and by activity level.”
That sentence is the first casualty of every headline written about this paper, and it’s the most important one in it.
The line at 65
Large cohort studies have found higher mortality among people aged 50–65 with high animal-protein intake — but in the over-65 group, the association reverses entirely.
Physiologically this makes complete sense. The older you are, the more protein it takes to switch on muscle protein synthesis at all. The phenomenon is called anabolic resistance: a response a young adult can trigger with 20 grams in a meal may take an older adult 30 to 40.
Which is why the international consensus positions (PROT-AGE, ESPEN) recommend 1.0–1.2 g/kg for healthy older adults, rising to 1.2–1.5 g/kg during illness or hospitalisation.
Two opposite mistakes, same clinic
In recent years I’ve seen two kinds of patient walk into the same consulting room, doing exactly opposite things, and both in trouble.
The first: afraid of dialysis, fractured a hip instead
A routine screen shows reduced kidney function. A neighbour says protein causes dialysis. From that day: no meat, no soy milk, eventually no eggs. Three years on, kidney function genuinely hasn’t worsened much — but the weight is down, the walking is slower, the stairs need a handrail, and eventually there’s a fall in the bathroom. On admission, grip strength and gait speed both meet the criteria for sarcopenia.
She got half of it right. She shouldn’t have been eating in excess. But she turned “moderate” into “almost none,” and the price was her ability to walk unaided.
The second: loading up on protein, unaware he was already stage 3
Mid-fifties, started lifting two years ago, one or two whey shakes a day. A workplace screen turns up proteinuria and an eGFR already in stage 3 — diabetic kidney disease. His first question to me was whether the protein powder had done it.
In people with normal kidney function, there is no clear evidence that high protein intake causes kidney disease. His problem was different: he already had diabetes, he already had kidney damage, and he’d spent two years well above the recommended ceiling without knowing it. The protein powder wasn’t the problem. Never having checked his kidney function was.
Where kidney patients fall through the gap
The KDIGO 2024 guideline recommends that adults with CKD stages 3–5 maintain 0.8 g/kg per day, and avoid exceeding 1.3 g/kg.
Put that number on the same axis as the new US band of 1.2–1.6, and the gap is hard to miss.
| Group | Per kg body weight, per day |
|---|---|
| Adults, sedentary | 1.0 – 1.2 g |
| Adults, resistance-trained | 1.2 – 1.6 g |
| Age 65+, healthy | 1.0 – 1.2 g, paired with training |
| Age 65+, ill or hospitalised | 1.2 – 1.5 g |
| CKD stages 3–5 | 0.8 g; avoid exceeding 1.3 |
| On dialysis | 1.0 – 1.2 g |
Patients already on dialysis are advised to take 1.0–1.2 g/kg — more than the average adult, to guard against protein-energy wasting, which is among the strongest predictors of mortality in this population. Change the stage and you change the answer: after dialysis starts, the danger isn’t eating too much. It’s not eating enough.
Taiwan is a useful place to watch this play out. Our dialysis incidence and prevalence have sat near the top of the global rankings for years, with more than 90,000 people on dialysis. The average age at initiation is around 68, and over 60% of new patients are 65 or older.
Which means the population that most needs kidney protection and the population that most needs adequate protein are, to a large degree, the same people. Any population-average recommendation needs recalibrating before it touches that group.
Without training, the grams barely matter
The review notes that athletes take in large amounts of protein without developing metabolic disease, and proposes that regular exercise is doing the protecting. That matches what I see clinically.
Resistance training is currently the only intervention with consistent randomised-trial evidence for improving strength, physical function and fall risk in older adults. And the gains from protein supplementation on muscle mass and strength are clearest when it’s paired with resistance training.
Muscle mass isn’t muscle function.
But muscle function is independence.
The patient who fell didn’t lose weight. She lost the ability to walk into her own bathroom. That, not the number on a scale, is the endpoint geriatric medicine actually cares about.
Pregnant and breastfeeding women; children and adolescents; anyone post-surgery, healing a wound, or in acute infection; anyone with existing sarcopenia, frailty or unintentional weight loss; patients undergoing cancer treatment; dialysis patients; anyone with metabolically unstable CKD; and older adults whose intake is already low.
In these groups, protein restriction isn’t a cautious longevity strategy. It’s clear clinical harm.
Test first, then talk about eating
If only one line survives this piece, I’d like it to be this one.
Taiwan’s CKD prevalence has been estimated at roughly 11.9%, with awareness among those screened at just 3.5%. For every hundred people whose kidney function is already impaired, three or four know it. The other ninety-odd are adjusting their diets based on whatever they read online — and whichever direction they adjust, they’re guessing.
Ask for two things at your next check-up: serum creatinine (for estimated GFR) and a urine albumin-to-creatinine ratio (UACR). Especially if you have diabetes, hypertension, a family history of kidney disease, or a long habit of painkillers or supplements.
Whatever number the US settles on, whatever the next review concludes, every one of these conversations rests on a single precondition: that you know your own kidney function.
Test first, then talk about eating. Do it the other way round and you’re guessing.
References
- Knopf BA, Lamming DW. The Hallmarks of Protein and Amino Acid Restriction in Aging and Longevity. Cell Press Blue. 2026. DOI: 10.1016/j.cpblue.2026.100079
- Levine ME, et al. Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population. Cell Metab. 2014;19(3):407-417.
- Green CL, et al. Dietary restriction of isoleucine increases healthspan and lifespan of genetically heterogeneous mice. Cell Metab. 2023;35(11):1976-1995.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117-S314.
- KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update. Am J Kidney Dis. 2020;76(3 Suppl 1):S1-S107.
- Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people (PROT-AGE). J Am Med Dir Assoc. 2013;14(8):542-559.
- Morton RW, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. Br J Sports Med. 2018;52(6):376-384.
- Wen CP, et al. All-cause mortality attributable to chronic kidney disease. Lancet. 2008;371(9631):2173-2182.
This article is general health information and not individual medical advice. The patient accounts are composites drawn from multiple cases and do not describe any specific individual. Any dietary change — particularly for people with chronic kidney disease or diabetes, or for older adults — should be discussed with your own physician or dietitian.