Vitamin C's Impact on Kidney Stones

Overseen By Demond Wiley

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: University of Alabama at Birmingham

Must be taking: Thiazides, Citrate supplementation

Disqualifiers: Diabetes, Hypertension, Gout, others

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

Compensation: Varies

Number of Visits: 6

Duration: 4 days

136 Participants Needed

Trial Summary

What is the purpose of this trial?

The purpose of this basic research study is to determine the contribution of endogenous ascorbic acid (AA) turnover to urinary oxalate excretion in both normal BMI and obese adult non-stone formers and calcium oxalate stone formers. The studies proposed will use diets of known nutrient composition, a stable isotope of ascorbic acid (13C6-AA) and mass spectrometric techniques to quantify ascorbic acid turnover to oxalate.

Will I have to stop taking my current medications?

The trial requires participants to stop taking supplements like vitamins, calcium, and other minerals for 2 weeks before and during the study. If you are on medications for stone prevention, you must have been on a stable dose for at least 8 weeks before the study, and if you take allopurinol, you need to stop it 2 weeks before the study.

What data supports the effectiveness of the treatment Carbon-13 Ascorbic Acid Oral Load for kidney stones?

Some studies suggest that high doses of vitamin C do not increase the risk of kidney stones due to the body's ability to regulate vitamin C absorption and conversion to oxalate. In fact, a large study found that people with high vitamin C intake had a lower risk of kidney stones. ^{1 2 3 4 5}

Is Vitamin C safe for people with kidney stones?

Vitamin C is generally safe for healthy people, but high doses may increase the risk of kidney stones in those with existing kidney issues or a history of stones. People with kidney problems should limit their intake to about 100 mg per day. ^{2 3 6 7 8}

How does the drug Carbon-13 Ascorbic Acid Oral Load differ from other treatments for kidney stones?

Carbon-13 Ascorbic Acid Oral Load is unique because it uses a labeled form of vitamin C to study its impact on kidney stones, focusing on how the body processes vitamin C and its potential role in stone formation. Unlike other treatments, this approach helps researchers understand the metabolic pathways and risks associated with vitamin C intake, which is still debated in the context of kidney stones. ^{2 3 4 5 6}

Research Team

John Knight

Principal Investigator

University of Alabama at Birmingham

Eligibility Criteria

This trial is for adults with normal BMI or obese, non-stone formers and calcium oxalate stone formers who haven't had certain health conditions like diabetes, hypertension, or severe kidney issues. Participants must not be on specific medications that could affect the study results and should agree to follow a controlled diet without supplements or vigorous exercise during the study.

Inclusion Criteria

Able to provide informed consent

Your fasting blood test results are normal for a comprehensive metabolic panel (CMP).

Willingness to not undertake vigorous exercise during the study

Exclusion Criteria

Your kidney function is too low (eGFR less than 60ml/min/1.73m2).

I have been diagnosed with primary hyperoxaluria.

I have high blood pressure.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

1-2 weeks

1 visit (in-person)

Dietary Equilibration

Participants consume a controlled diet low in oxalate and ascorbic acid for two days to equilibrate

2 days

1 visit (in-person)

Treatment

Participants ingest an oral load of carbon-13 ascorbic acid and undergo serial blood and urine collections

4 days

4 visits (in-person)

Follow-up

Participants are monitored for safety and effectiveness after treatment

1-2 weeks

Treatment Details

Interventions

• Carbon-13 Ascorbic Acid Oral Load
• Low Oxalate Diet

Trial Overview The study aims to understand how much vitamin C (ascorbic acid) from our diet turns into oxalate in the urine, which can contribute to kidney stones. It involves following a special low-oxalate diet and taking a stable isotope of ascorbic acid orally while researchers measure its turnover using advanced techniques.

Participant Groups

Group I: Controlled Dietary Study Experimental Treatment 2 Interventions

Subjects will consume a controlled diet (low in oxalate and ascorbic acid) for six days. After two days of equilibration, subjects will provide a blood sample and ingest an oral load of ascorbic acid (1 mg/kg) with breakfast on Day 3. The following day (Day 4), serial blood and urine collections will occur. On Days 5 through 7, subjects will complete a 24-hr urine collection and blood draw.

Who Is Running the Clinical Trial?

University of Alabama at Birmingham

Lead Sponsor

Trials

1,677

Recruited

2,458,000+

Findings from Research

Ascorbic acid (AA) supplementation significantly lowered urinary pH in stone-forming patients, from 7.6 to 6.9, which may influence the formation of certain types of kidney stones.

Despite the reduction in urinary pH, 33.3% of patients developed new kidney stones, indicating that while AA may alter urine acidity, it does not necessarily prevent stone formation and could lead to complications like hyperoxaluria in some cases.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Is it safe to prescribe ascorbic acid for urinary acidification in stone-forming patients with alkaline urine? Noureldin, YA., da Silva, A., Fahmy, N., et al.[2020]

A male subject who consumed large doses of vitamin C for 8 days experienced a 350% increase in oxalate excretion, leading to calcium oxalate crystalluria and haematuria, indicating a significant risk associated with high vitamin C intake.

The study highlights that high doses of vitamin C can lead to increased calcium oxalate supersaturation in urine, suggesting that clinicians should be cautious about recommending large doses of vitamin C due to the potential for kidney stone formation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Relative hyperoxaluria, crystalluria and haematuria after megadose ingestion of vitamin C. Auer, BL., Auer, D., Rodgers, AL.[2019]

High doses of vitamin C do not increase the risk of calcium oxalate kidney stones due to the body's ability to regulate absorption and metabolism of ascorbic acid, which limits oxalate production.

In a large study, individuals consuming more than 1,500 mg of vitamin C daily actually had a lower risk of developing kidney stones compared to those with lower intakes, suggesting a protective effect in the general population.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

No contribution of ascorbic acid to renal calcium oxalate stones. Gerster, H.[2022]

In a study involving 156,735 women and 40,536 men over a median follow-up of 11.3 to 11.7 years, high total and supplemental vitamin C intake was linked to an increased risk of kidney stones in men, particularly at doses of 1,000 mg/day or more.

Conversely, no significant association was found between vitamin C intake and kidney stones in women, suggesting that the effects of vitamin C on kidney stone risk may differ by sex.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. Ferraro, PM., Curhan, GC., Gambaro, G., et al.[2018]

In a study involving 47 calcium stone-forming patients and 20 healthy subjects, vitamin C supplementation (1 g or 2 g) significantly increased urinary oxalate levels, suggesting a potential risk for calcium oxalate stone formation.

Despite the increase in urinary oxalate, urinary pH remained unchanged after vitamin C supplementation, indicating that the mechanism of increased oxalate excretion does not involve changes in urine acidity.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of vitamin C supplements on urinary oxalate and pH in calcium stone-forming patients. Baxmann, AC., De O G Mendonça, C., Heilberg, IP.[2016]

Ascorbic acid (AA) supplements are associated with a significantly higher risk of kidney stones in men, with an odds ratio of 1.62, indicating that men taking AA supplements may be more likely to develop kidney stones compared to women.

In contrast, AA supplements do not show a significant correlation with kidney stone risk in women, suggesting that the effects of AA may differ by gender and highlighting the need for further research to confirm these findings.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Ascorbic Acid Supplements and Kidney Stones Incidence Among Men and Women: A systematic review and meta-analysis. Jiang, K., Tang, K., Liu, H., et al.[2020]

In a study involving guinea pigs, ascorbic acid supplementation at doses of 10, 40, and 60 mg per 100g body weight per day for 105 days did not lead to crystalluria, calcification, or stone formation, confirming its safety in the doses typically used by clinicians.

However, when ascorbic acid was given to animals with induced hypercalciuria and hyperoxaluria for 45 days, it worsened calcification in renal and bladder tissues, suggesting caution in its use under certain conditions.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Ascorbic acid is an abettor in calcium urolithiasis: an experimental study. Singh, PP., Kiran, R., Pendse, AK., et al.[2013]

Ingesting large doses of vitamin C (ascorbic acid) does not appear to cause significant adverse health effects in healthy individuals, despite concerns about issues like kidney stones and vitamin B12 destruction.

However, high doses of ascorbic acid should be avoided in people with certain health conditions, such as renal insufficiency or those prone to kidney stones, indicating the need for caution in specific populations.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Safety of high-level vitamin C ingestion. Rivers, JM.[2013]

References

1. Turkey pubmed.ncbi.nlm.nih.gov

Is it safe to prescribe ascorbic acid for urinary acidification in stone-forming patients with alkaline urine? [2020]

2. England pubmed.ncbi.nlm.nih.gov

Relative hyperoxaluria, crystalluria and haematuria after megadose ingestion of vitamin C. [2019]

3. Switzerland pubmed.ncbi.nlm.nih.gov

No contribution of ascorbic acid to renal calcium oxalate stones. [2022]

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

Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. [2018]

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

Effect of vitamin C supplements on urinary oxalate and pH in calcium stone-forming patients. [2016]

6. Iran pubmed.ncbi.nlm.nih.gov

Ascorbic Acid Supplements and Kidney Stones Incidence Among Men and Women: A systematic review and meta-analysis. [2020]

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

Ascorbic acid is an abettor in calcium urolithiasis: an experimental study. [2013]

8. Canada pubmed.ncbi.nlm.nih.gov

Safety of high-level vitamin C ingestion. [2013]