Diet and Oxalate Absorption for Kidney Stones

Recruiting at 1 trial location

Overseen By Sonia Fargue, PhD

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: University of Alabama at Birmingham

Must not be taking: Immunosuppressants, NSAIDs

Disqualifiers: Chronic kidney disease, Diabetes, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 5

80 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to determine if individuals with calcium oxalate kidney stones absorb more oxalate from their diet, potentially increasing oxalate levels in their urine. Participants will follow specific diets, one low and one moderately high in oxalate, to observe their body's response. The trial is open to adults with a history of calcium oxalate kidney stones and healthy individuals without such a history. As an unphased trial, it offers participants an opportunity to contribute to understanding how diet affects kidney stone formation.

Will I have to stop taking my current medications?

The trial requires participants to stop taking supplements like vitamins, calcium, and herbal supplements for 2 weeks before and during the study. The protocol does not specify if you need to stop other medications, so it's best to discuss with the study team.

What prior data suggests that these dietary interventions and tests are safe for participants?

Research has shown that consuming many foods high in oxalates can affect kidney health. Some studies suggest that excessive dietary oxalate may lead to kidney problems and injuries. High oxalate levels could also worsen chronic kidney disease. However, these studies primarily examine long-term effects, not short-term risks.

Conversely, a low-oxalate diet appears beneficial for kidney health. Research indicates it can aid those with kidney stones and may reduce the risk of developing more stones.

Overall, both high and low oxalate diets are generally safe for short-term use in studies like this one. Participants in similar studies have not reported major safety issues with either diet. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about this trial because it explores how different diets affect oxalate absorption in people with idiopathic calcium oxalate kidney stones. Unlike current treatments that often focus on medications or surgical options, this trial investigates dietary adjustments as a potential method to manage kidney stone formation. By comparing high-oxalate and low-oxalate diets, researchers aim to uncover how dietary oxalate impacts stone formation, potentially offering a natural and non-invasive strategy for prevention. The study could lead to personalized dietary recommendations that empower individuals to manage their kidney stone risk through simple changes in their eating habits.

What evidence suggests that this trial's diets and tests could be effective for studying oxalate absorption in kidney stone patients?

This trial will compare the effects of high-oxalate and low-oxalate diets on oxalate absorption in individuals with and without a history of kidney stones. Research has shown that consuming many high-oxalate foods, such as spinach and nuts, can increase urinary oxalate levels, potentially leading to kidney stones. Conversely, studies suggest that reducing high-oxalate foods can lower this risk. Individuals on a low-oxalate diet often have less oxalate in their urine, reducing the likelihood of kidney stones. Additionally, adequate dietary calcium can decrease oxalate absorption and support kidney health. ^{1 3 6 7 8}

Who Is on the Research Team?

Sonia Fargue, M.D., Ph.D.

Principal Investigator

University of Alabama at Birmingham

Are You a Good Fit for This Trial?

This trial is for adults who've had calcium oxalate kidney stones and healthy volunteers without a history of these stones. Participants will follow specific diets and undergo tests to study how their bodies handle oxalate.

Inclusion Criteria

Body Mass Index > 18.5 kg/m2

Normal fasting serum electrolytes on comprehensive metabolic profile

Willing to ingest fixed diets

Exclusion Criteria

My blood pressure or diabetes is not well-controlled.

My kidney function is severely reduced.

I have type 1 diabetes.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

1 visit (in-person)

Low-oxalate diet and initial tests

Participants ingest a controlled low-oxalate diet for 5 days and collect urine samples for analysis

5 days

2 visits (in-person)

13C2-Oxalate gut absorption test

Participants undergo the 13C2-oxalate absorption test with hourly blood and urine collections

1 day

1 visit (in-person)

Wash-out period

Participants have a wash-out period where they eat freely before the next phase

1 week

High-oxalate diet

Participants consume a high-oxalate diet for 4 days and collect urine samples for analysis

4 days

1 visit (in-person)

Follow-up

Participants are monitored for safety and effectiveness after the dietary interventions

2 weeks

What Are the Treatments Tested in This Trial?

Interventions

• High-oxalate diet
• Low-oxalate diet
• soluble oxalate gut absorption test

Trial Overview

The trial involves participants eating low and high-oxalate diets for five days each, taking an oxalate absorption test with sugar solutions, and providing urine, blood, stool, and breath samples to measure the effects.

How Is the Trial Designed?

Group I: Idiopathic Calcium Oxalate Kidney Stone Patients Experimental Treatment 3 Interventions

Low and High oxalate fixed diets. Soluble oxalate absorption test.

Group II: Healthy non-kidney stone forming individuals Active Control 3 Interventions

Low and High oxalate fixed diets. Soluble oxalate absorption test.

Who Is Running the Clinical Trial?

University of Alabama at Birmingham

Lead Sponsor

Trials

1,677

Recruited

2,458,000+

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Collaborator

Trials

2,513

Recruited

4,366,000+

University of Texas Southwestern Medical Center

Collaborator

Trials

1,102

Recruited

1,077,000+

Published Research Related to This Trial

In an animal study with male Sprague-Dawley rats, a diet high in hydroxy-L-proline, a precursor of oxalate, led to increased urinary oxalate levels and the formation of calcium oxalate crystals in the kidneys, indicating a direct link between dietary oxalate and kidney stone formation.

When the dietary oxalate was reduced, there was a significant decrease in urinary oxalate and associated kidney crystal deposits, suggesting that cutting back on oxalate can improve kidney function and reduce the risk of stone recurrence.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dietary oxalate and calcium oxalate nephrolithiasis. Khan, SR., Glenton, PA., Byer, KJ.[2013]

A high-oxalate diet significantly increases oxalate absorption in healthy individuals, with absorption rates nearly doubling from 7.9% on a low-oxalate diet to 13.7% on a high-oxalate diet, based on a study of 25 volunteers.

After 6 weeks on a high-oxalate diet, oxalate absorption decreased, suggesting that prolonged exposure may lead to adaptation, but absorption rates returned to high levels after a wash-out period, indicating the potential for dietary management in hyperoxaluria.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Influence of a high-oxalate diet on intestinal oxalate absorption. Zimmermann, DJ., Hesse, A., von Unruh, GE.[2018]

In a study of 60 calcium renal-stone formers, higher dietary intake of carbohydrates and fats was positively correlated with increased urinary oxalate excretion, suggesting these nutrients may influence stone formation.

Conversely, calcium intake was found to be inversely correlated with urinary oxalate excretion, indicating that higher calcium consumption may help reduce oxalate levels in urine, while protein intake showed minimal impact.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of dietary intake on urinary oxalate excretion in calcium renal stone formers. Masai, M., Ito, H., Kotake, T.[2019]

Restricting dietary oxalate intake can help reduce the risk of calcium oxalate kidney stones, especially in individuals who absorb oxalate at high rates; only a few specific foods like spinach and chocolate significantly increase urinary oxalate excretion.

Increasing calcium intake may help lower urinary oxalate levels by binding oxalate in the gut, suggesting that a balanced approach to calcium and oxalate consumption is important for effective dietary management of kidney stone risk.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of dietary oxalate and calcium on urinary oxalate and risk of formation of calcium oxalate kidney stones. Massey, LK., Roman-Smith, H., Sutton, RA.[2022]

In a study involving 108 pediatric patients, those with idiopathic calcium oxalate urolithiasis showed significantly higher intestinal oxalate absorption compared to healthy controls and patients with primary hyperoxaluria, indicating that increased absorption is a key risk factor for this condition.

The research found that while idiopathic stone formers had a correlation between intestinal oxalate absorption and urinary excretion, patients with primary hyperoxaluria did not, suggesting that dietary restrictions should focus on high-oxalate foods for those with primary hyperoxaluria instead.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[13C2]oxalate absorption in children with idiopathic calcium oxalate urolithiasis or primary hyperoxaluria. Sikora, P., von Unruh, GE., Beck, B., et al.[2013]

The review highlights that the primary difference between individuals who form calcium oxalate kidney stones and those who do not is in how their intestines absorb oxalate from food.

Future research is expected to focus on dietary oxalate intake and kidney excretion of oxalate, which could provide clearer insights into the role of dietary oxalate in kidney stone formation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The impact of dietary oxalate on kidney stone formation. Holmes, RP., Assimos, DG.[2018]

A normal-calcium, low-animal protein, low-salt diet significantly reduced oxalate excretion in patients with idiopathic calcium oxalate nephrolithiasis, decreasing mean oxaluria from 50.2 to 35.5 mg/d over 3 months.

In comparison, a traditional low-oxalate diet only reduced oxaluria from 45.9 to 40.2 mg/d, indicating that the new diet may be more effective in managing hyperoxaluria.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Diet to reduce mild hyperoxaluria in patients with idiopathic calcium oxalate stone formation: a pilot study. Nouvenne, A., Meschi, T., Guerra, A., et al.[2022]

In a study involving 240 participants (120 healthy volunteers and 120 patients with calcium oxalate stones), it was found that patients absorbed significantly more oxalate (10.2%) compared to healthy individuals (8.0%), indicating a potential link between oxalate absorption and stone formation.

The research suggests that high oxalate absorption is associated with increased oxalate excretion, which may elevate the risk of developing calcium oxalate stones, highlighting the importance of dietary oxalate management in susceptible individuals.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Intestinal oxalate absorption is higher in idiopathic calcium oxalate stone formers than in healthy controls: measurements with the [(13)C2]oxalate absorption test. Voss, S., Hesse, A., Zimmermann, DJ., et al.[2022]

A study involving 10 healthy participants found that a high calcium diet (1,000 mg daily) led to higher urinary calcium levels and lower urinary oxalate levels compared to a low calcium diet (400 mg daily) while consuming a liberal oxalate diet.

Despite lower oxalate levels, the overall urinary saturation of calcium oxalate was significantly higher on the high calcium diet, suggesting that such a diet may increase the risk of calcium oxalate stone formation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of high and low calcium diets on stone forming risk during liberal oxalate intake. Matsumoto, ED., Heller, HJ., Adams-Huet, B., et al.[2013]

In a study of 22 patients with hyperoxaluria, both dietary changes and calcium citrate supplementation significantly reduced urinary oxalate excretion, indicating effective management of this condition.

Importantly, urinary calcium excretion remained unchanged in both groups, suggesting that dietary calcium modifications can help lower oxalate levels without increasing the risk of calcium-related issues.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of dietary changes on urinary oxalate excretion and calcium oxalate supersaturation in patients with hyperoxaluric stone formation. Penniston, KL., Nakada, SY.[2022]

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