Oxalate-Controlled Diets for Kidney Stones

Overseen By Tanecia Mitchell, PhD

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: University of Alabama at Birmingham

Must be taking: Thiazides, Citrate supplementation

Must not be taking: Antibiotics, Allopurinol

Disqualifiers: Tobacco use, Pregnancy, Active illness, others

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

Compensation: Varies

Number of Visits: 14

88 Participants Needed

Trial Summary

What is the purpose of this trial?

This study is looking to understand the role of oxalate on kidney stone development and immunity. This study will enroll healthy participants and participants with calcium oxalate kidney stones (CaOx KS). Participants will be in this study for about 3 weeks, consume controlled diets, and provide blood and urine specimens.

Do I have to stop taking my current medications for the trial?

The trial requires that if you are on medications for kidney stone prevention, you must be on a stable dose for at least 8 weeks before and during the study. You should not take allopurinol for 2 weeks before the study. Other medications are not specifically mentioned, so it's best to discuss with the study team.

What data supports the effectiveness of oxalate-controlled diets for kidney stones?

Research shows that a low oxalate diet can significantly reduce the amount of oxalate in urine, which is a key factor in forming calcium oxalate kidney stones. Studies found that patients on a low oxalate diet had a greater reduction in urinary oxalate compared to those taking supplements, suggesting that dietary changes are effective in managing kidney stone risk. ^{1 2 3 4 5}

Is an oxalate-controlled diet safe for humans?

Oxalate-controlled diets, which involve adjusting the intake of foods high in oxalate, are generally safe for humans. However, it's important to balance calcium intake, as restricting calcium can increase oxalate absorption, potentially leading to kidney stones. Always consult with a healthcare provider before making significant dietary changes. ^{4 6 7 8 9}

How does an oxalate-controlled diet differ from other treatments for kidney stones?

An oxalate-controlled diet is unique because it focuses on managing the intake of oxalate-rich foods to reduce the risk of calcium oxalate kidney stones, unlike other treatments that may not address dietary factors. Increasing dietary calcium can help bind oxalate in the gut, reducing its absorption and excretion, which is a different approach compared to medications or surgical interventions. ^{1 2 6 8 10}

Research Team

Tanecia Mitchell, PhD

Principal Investigator

University of Alabama at Birmingham

Eligibility Criteria

This trial is for adults aged 18-60 with a BMI of 20-30, not using tobacco or pregnant. It includes healthy individuals and those with calcium oxalate kidney stones who are willing to follow specific diets provided by the study and avoid vigorous exercise. Participants must be able to give informed consent, have normal blood tests, and collect accurate urine samples.

Inclusion Criteria

Willing to consume diets provided only by the UAB CCTS Bionutrition Core

I am between 18 and 60 years old.

You need to have normal results for certain blood and urine tests taken after fasting.

Exclusion Criteria

I have taken medications or supplements recently and do not have conditions affecting oxalate processing.

I have not had any infections like COVID-19 or the flu in the last 14 days.

I do not meet all the required conditions or my doctor advised against it.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

1 week

Dietary Intervention

Participants receive either a high or low oxalate diet for 4 days, followed by a 6-day washout period, and then crossover to the opposite diet for another 4 days

14 days

Daily monitoring for dietary adherence

Follow-up

Participants are monitored for changes in urinary oxalate, nanocrystalluria, and monocyte subtypes

1 week

Final assessment on Day 14

Treatment Details

Interventions

• High Oxalate Diet
• Low Oxalate Diet

Trial Overview The study aims to understand how dietary oxalate affects kidney stone formation and immune responses. For about three weeks, participants will consume either a low or high oxalate diet while providing blood and urine samples for analysis.

Participant Groups

Group I: Healthy Participants Experimental Treatment 2 Interventions

Healthy participants will randomly receive either high (250mg) or low (40mg) oxalate diet for for four days, a ten day "washout" period on a self-selected diet, and finally the opposite diet from the first for the last four days.

Group II: Calcium Oxalate Kidney Stone Experimental Treatment 2 Interventions

Calcium oxalate kidney stone participants will randomly receive either high (250mg) or low (40mg) oxalate diet for for four days, a ten day "washout" period on a self-selected diet, and finally the opposite diet from the first for the last four days.

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+

National Institutes of Health (NIH)

Collaborator

Trials

2,896

Recruited

8,053,000+

Findings from Research

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]

A low-oxalate diet significantly reduced urinary oxalate levels more effectively than supplementation with vitamin B6 and magnesium in patients with idiopathic hyperoxaluria, with a median reduction of 31.1% compared to 16.0% for supplementation alone.

Combination therapy of a low-oxalate diet and supplementation did not provide additional benefits over the diet alone, indicating that dietary modification is the preferred approach for managing urinary oxalate levels in stone formers.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Prospective Randomized Evaluation of Idiopathic Hyperoxaluria Treatments. Gupta, M., Gallante, B., Bamberger, JN., et al.[2022]

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]

Recent studies indicate that increasing calcium intake may actually lower the risk of forming calcium oxalate stones, contrary to previous beliefs that recommended limiting calcium.

A large randomized trial found that individuals with normal calcium intake, along with lower protein and salt consumption, experienced significantly fewer recurrences of calcium oxalate stones, suggesting that dietary changes can effectively reduce stone risk.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Calcium oxalate kidney stones: another reason to encourage moderate calcium intakes and other dietary changes. Moyad, MA.[2013]

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]

Dietary counseling is crucial for preventing kidney stones, particularly calcium oxalate stones, which are the most common type, and should focus on modifiable dietary factors.

Individuals with a history of calcium-containing kidney stones should maintain adequate fluid intake (at least 2 liters of urine per day) and not restrict calcium intake, as a minimum of 800 mg/day is recommended to prevent negative health effects.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dietary factors and kidney stone formation. Curhan, GC., Curhan, SG.[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]

Dietary factors such as high intake of animal proteins, oxalate, and sodium, along with low fluid and potassium intake, contribute to the formation of calcium oxalate stones, highlighting the importance of dietary modification in prevention.

For patients with severe metabolic issues or ineffective dietary changes, pharmacologic treatments like thiazide or indapamide with potassium citrate are recommended for those with high calcium levels in urine, while potassium citrate alone is suggested for others.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Medical management of urinary stone disease. Pak, CY.[2022]

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]

References

1. United States pubmed.ncbi.nlm.nih.gov

Effect of high and low calcium diets on stone forming risk during liberal oxalate intake. [2013]

2. United States pubmed.ncbi.nlm.nih.gov

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

3. United States pubmed.ncbi.nlm.nih.gov

Prospective Randomized Evaluation of Idiopathic Hyperoxaluria Treatments. [2022]

4. United States pubmed.ncbi.nlm.nih.gov

Dietary oxalate and calcium oxalate nephrolithiasis. [2013]

5. United States pubmed.ncbi.nlm.nih.gov

Calcium oxalate kidney stones: another reason to encourage moderate calcium intakes and other dietary changes. [2013]

6. United States pubmed.ncbi.nlm.nih.gov

Effect of dietary oxalate and calcium on urinary oxalate and risk of formation of calcium oxalate kidney stones. [2022]

7. United States pubmed.ncbi.nlm.nih.gov

Dietary factors and kidney stone formation. [2013]

8. Germany pubmed.ncbi.nlm.nih.gov

Influence of a high-oxalate diet on intestinal oxalate absorption. [2018]

9. Switzerland pubmed.ncbi.nlm.nih.gov

Medical management of urinary stone disease. [2022]

10. United States pubmed.ncbi.nlm.nih.gov

Diet to reduce mild hyperoxaluria in patients with idiopathic calcium oxalate stone formation: a pilot study. [2022]