Without preventive treatment, 30 to 50 percent of people who have had a kidney stone will form another within five years. Prevention works by increasing urine volume or changing the concentration of key risk factors in the urine — calcium, oxalate, uric acid, and citrate. The question the trial tackled is how to choose the targets: use the same general advice for everyone (the empiric approach), or use a 24-hour urine collection to find each person's specific abnormalities (the targeted approach).
In the trial, adults with recurrent stone disease completed a 24-hour urine test and were then randomized. The empiric group received standard, guideline-based diet and medication advice. The targeted group's plan was built around their three most severe urine abnormalities. Researchers measured changes in diet and urine parameters from baseline to eight weeks.
The differences appeared quickly and in the direction the personalized approach predicted. In the empiric group, dietary oxalate intake fell by 33 percent, but water, sodium, animal protein, and fruit and vegetable intake did not change significantly — and neither did urine volume or sodium excretion. In the targeted group, daily water intake rose by 17 percent, fruit and vegetable intake doubled, and both oxalate and sodium intake dropped. In the urine, the targeted group reduced calcium-oxalate supersaturation by 38 percent, versus 30 percent in the empiric group.
Two limits belong in the reading. This is an eight-week study of diet and urine markers — it does not follow patients long enough to count actual stone recurrences. And the sample was adults with recurrent disease, so the results do not necessarily transfer to a first-stone patient. What the trial does establish is a mechanism: a plan built on your own urine numbers changes more of the right variables than a one-size-fits-all plan.
For most people, the targeted idea does not require waiting for a study. It requires asking your care team for the test: a 24-hour urine collection after a stone episode is the standard way to find out whether your problem is oxalate, calcium, uric acid, low citrate, or low volume. The stone plan that follows is then built on that column — the oxalate-avoider and the uric-acid-controller eat different plates, and both eat better than the person following generic advice.
Until the test is done, the empiric baseline is still useful: normal dietary calcium at meals, lower added salt, moderate animal protein, plenty of fluid, and citrus for citrate. The trial's message is that the baseline is a floor, not the finished plan — the targeted version of the plate is where the bigger changes happened.
The table below shows the measured oxalate values of the foods the two approaches adjust differently.
| Food | Oxalate (mg) | Serving | Rating |
|---|---|---|---|
| Spinach, cooked | 493 | 1/2 cup | Avoid |
| Beets, boiled or pickled | 48 | 1/2 cup | Caution |
| Sweet potato, baked | 20 | 1/2 cup | Safe |
| Potato, boiled | 7 | 1/2 cup | Safe |
| Broccoli, boiled | 4 | 1/2 cup | Safe |
| Carrots, cooked | 9 | 1/2 cup | Safe |
| Apple, fresh | 2 | 1 medium | Safe |
| Banana | 6 | 1 medium | Safe |
| Lentils, cooked | 8 | 1/2 cup | Safe |
| Brown rice, cooked | 4 | 1/2 cup | Safe |
The trial's bottom line is a single practical question you can take to your clinician: "Can I do a 24-hour urine test to target my stone prevention?" For people with recurrent stones, the answer should usually be yes — the test is the standard tool for turning generic advice into a personal plan. The eight-week data in this trial suggest that the personal plan is also the one that changes more of the diet and urine variables that matter.
You collect all urine for 24 hours, and the lab measures calcium, oxalate, uric acid, citrate, sodium, and volume. The results show which risk factors are elevated for you specifically, which lets a clinician target your diet and medication plan.
In this eight-week trial, the targeted group made bigger diet changes — more water, double the fruit and vegetables, less oxalate and sodium — and lowered calcium-oxalate supersaturation further than the empiric group. Longer follow-up is still needed to confirm the effect on actual recurrences.
Yes. The evidence-based baseline — dietary calcium at meals, lower salt, moderate protein, plenty of fluids, citrus for citrate — is a safe starting point. The 24-hour test then refines it into the targeted version.
See how oxalate values are measured and verified on our data methodology page.