How Much Vitamin C Is Enough? Landmark Study Reveals Blood Levels, Dosing, and Urinary Loss
Dr. Kumar’s Take:
This landmark NIH study shows that plasma vitamin C levels rise steeply with low-to-moderate doses, then plateau at higher intakes. Most people reach near-maximal blood levels with just 200 mg daily, and above 400 mg/day, your body starts dumping the extra in urine. For optimal absorption and benefit, aim for 200 mg daily from food or supplements.
Key Takeaways:
✔ Plasma vitamin C increases quickly with doses up to 100 mg/day, then plateaus at higher intakes.
✔ Maximal white blood cell (immune cell) saturation occurs at 100 mg/day; plasma is near-maximal at 200 mg/day.
✔ No vitamin C is lost in urine until about 100 mg/day; after 400 mg/day, most extra is excreted.
✔ High doses above 1000 mg/day may increase urine oxalate and uric acid, with no added benefit.