A critical finding in vitamin C research has implications for public health messaging: saturation of plasma vitamin C concentration and neutrophil accumulation occurs at approximately 200 mg per day in healthy individuals. Beyond this threshold, additional supplementation provides no measurable increase in immune cell function. Research by Carr and Maggini demonstrates that 100 mg daily achieves 68 percent saturation, while 50 mg achieves 42 percent. Most individuals consuming a varied diet containing citrus fruits, leafy greens, and other vitamin C-rich foods meet or exceed this saturation point without supplementation. This evidence-based saturation point undermines the widespread marketing of high-dose vitamin C supplements as immunity enhancers. For healthy populations, the biological ceiling at 200 mg daily suggests that excess supplementation represents wasted expense rather than enhanced protection. Read the full article on GMJ Newsroom.
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