From the Guidelines
For individuals with a history of kidney stone formation, taking 15 mg of vitamin C daily is considered safe, as it is well below the doses associated with increased risk of calcium oxalate stone formation. This recommendation is based on the understanding that higher vitamin C intake, typically above 1000 mg per day, can increase the risk of stone formation due to its metabolism to oxalate, as noted in a study published in Kidney International 1. The dose of 15 mg daily is significantly lower than the recommended dietary allowance and the upper limit of vitamin C intake, suggesting that the amount of additional oxalate produced would be minimal and unlikely to significantly increase stone risk. Key considerations for kidney stone formers include:
- Maintaining adequate hydration, such as drinking at least 2-3 liters of water daily
- Moderating intake of oxalate-rich foods
- Discussing specific situations with a healthcare provider, especially for those with recurrent kidney stones or rare metabolic conditions. According to 1, dietary vitamin C restriction is not recommended due to its presence in foods high in inhibitory factors like potassium, but supplemental vitamin C should be discontinued in calcium stone formers with hyperoxaluria.
From the Research
Safety of 15 mg Daily Vitamin C Intake for Kidney Stone Formers
- The daily intake of 15 mg of vitamin C is significantly lower than the amounts discussed in the studies 2, 3, 4 that investigated the relationship between vitamin C intake and kidney stone formation.
- A study from 1997 2 suggested that high doses of vitamin C do not increase the risk of calcium oxalate kidney stones due to physiological regulatory factors, but recommended that recurrent stone formers and patients with renal failure restrict daily vitamin C intakes to approximately 100 mg.
- Another study from 2023 3 found that higher vitamin C intake was inversely associated with stone formation, particularly at daily intake levels between 60 and 110 mg, and above 110 mg.
- There is no direct evidence from the provided studies that specifically addresses the safety of a 15 mg daily vitamin C intake for kidney stone formers, but the available data suggest that moderate to high vitamin C intake may not be harmful and could be beneficial for stone prevention 3.
- It is essential to consider individual factors, such as renal function and stone composition, when evaluating the safety of vitamin C supplementation for kidney stone formers, as some studies suggest that high vitamin C intake may be associated with an increased risk of kidney stones in certain populations 4.