From the Guidelines
Taking too much vitamin C can lead to an increased risk of kidney stone formation, particularly in individuals with hyperoxaluria, as it can be metabolized to oxalate, increasing urinary oxalate excretion by 22% with doses of 1000 mg twice daily 1.
Key Points to Consider
- The recommended dietary allowance for vitamin C is 75-90 mg per day for healthy adults, and excessive intake beyond 2000 mg per day can cause mild digestive issues like diarrhea, nausea, stomach cramps, and heartburn 1.
- High doses of vitamin C, over 3000 mg daily, may increase the risk of kidney stones in some individuals, especially those with a history of kidney problems.
- People with conditions like hemochromatosis should be cautious with high vitamin C intake as it can increase iron absorption.
- The body absorbs vitamin C more efficiently at lower doses, making high doses unnecessary and potentially harmful.
Recommendations
- Healthy adults should aim to get their daily vitamin C from fruits and vegetables rather than supplements to avoid excessive intake.
- Individuals with a history of kidney stones or hyperoxaluria should limit their vitamin C intake and avoid supplements, as suggested by a metabolic trial that demonstrated increased urinary oxalate excretion with high vitamin C doses 1.
- If experiencing digestive discomfort from vitamin C supplements, reduce the dosage or take it with food to minimize side effects.