The trial studied people with type 2 diabetes who already had advanced chronic kidney disease (stages 3b-4), randomizing them to a low-protein diet of 0.6 g/kg per day combined with ketoacid supplements — a formulation that provides the amino acid skeletons without the full nitrogen load. Over one year, the low-protein-plus-ketoacids group saw their kidney-function decline nearly halve compared with the comparison group, along with a significant drop in urine protein. Critically, the researchers reported no signs of malnutrition, which is the usual worry whenever protein is restricted.
Two limits belong in the reading. This is a study of people with diabetes and advanced CKD — a different population from a healthy person with a single kidney stone. And the protein target of 0.6 g/kg per day is a clinically supervised, disease-specific level, not a general recommendation. What transfers to the stone table is the underlying principle: excess protein — especially animal protein — is a measured kidney stressor, and moderation is the evidence-based position.
Protein matters for stones in a specific way: excess animal protein raises urinary calcium and uric acid and lowers urine pH and citrate, all of which favor stone formation. The stone plan's working number is moderation — roughly 0.8 to 1.4 g per kg per day, with animal protein kept to modest portions and plant protein favored. The low-protein CKD trial sits below that range and is for a different population, but it reinforces the direction: the protein column is worth watching, and the answer is portion, not pile-on.
The table below shows the measured oxalate values of the common protein sources — the animal proteins measure zero, and the plant proteins carry the low-oxalate check.
| Food | Oxalate (mg) | Serving | Rating |
|---|---|---|---|
| Eggs, whole | 0 | 2 large | Safe |
| Chicken breast, roasted | 0 | 3 oz | Safe |
| Salmon, baked | 0 | 4 oz | Safe |
| Tuna, canned in water | 0 | 3 oz | Safe |
| Greek yogurt, plain | 0 | 1 cup | Safe |
| Tofu, calcium-set | 10 | 1/2 cup | Safe |
| Lentils, cooked | 8 | 1/2 cup | Safe |
| Chickpeas, cooked | 4 | 1/2 cup | Safe |
| Peanut butter | 36 | 2 Tbsp | Caution |
| Almonds | 20 | 1 oz | Safe |
The stone patient does not need the trial's 0.6 g/kg target — that is a supervised CKD number. The transferable lesson is simpler: keep protein moderate, favor the zero-oxalate animal sources and the low-oxalate plant sources, and portion the handful that carry oxalate. The person who reads "low protein helps the kidney" as a reason to cut protein hard has over-corrected; the person who reads it as "moderate the protein and watch the oxalate column" has landed on the stone plan. The measured plate is the same plate: a palm of protein, the grain, the produce, and the dairy at the meal.
Moderate, don't eliminate. Excess animal protein raises urinary calcium and uric acid, but the stone plan's target is moderation (roughly 0.8-1.4 g/kg/day), not the very-low levels used under supervision in advanced CKD. Favor plant protein and keep animal portions modest.
Not directly — it studied people with type 2 diabetes and advanced CKD (stage 3b-4) at a supervised 0.6 g/kg/day target. If you have both diabetes and reduced kidney function, discuss protein targets with your clinician; a single stone history alone does not call for that level.
Eggs, chicken, fish, and Greek yogurt measure zero oxalate. The plant proteins — tofu, lentils, chickpeas — measure low oxalate and are the favored plant options. Portion the peanut butter and almonds.
See how oxalate values are measured and verified on our data methodology page.