Vitamin C for Runners: When it Helps, When it Hurts

# What this brief covers This summarizes research and practical guidance on vitamin C for runners: immune protection after heavy efforts, effects on recovery and soreness, the risk of blunting training adaptations, and sensible dosing and timing.

# The clear benefit: cut your post-race cold risk

Who benefits: runners undergoing heavy training or racing. Trials show no consistent benefit for the general population.

# What it does for recovery and soreness

Practical implication: prioritize sleep, whole foods, easy days, and time for recovery rather than relying on an antioxidant pill to make you feel better faster.

# The downside: high daily doses can blunt training gains Oxidative stress after a hard run is partly the signal your body uses to build more mitochondria—the cellular engines of endurance. Human trials show that taking about 1,000 mg of vitamin C daily (often paired with vitamin E in studies) can reduce the rise in mitochondrial proteins and cancel some endurance improvements across multiweek training blocks.

This is a trade-off: constant, large antioxidant doses can soften the very stimulus that produces aerobic adaptations. Over a full training block, that effect can quietly reduce the endurance you would otherwise gain.

# How much you actually need Most runners need only about 200 mg of vitamin C per day. A diet that includes five servings of fruit and vegetables easily provides that amount. Your body cannot make vitamin C, so you need a consistent dietary supply for collagen production and vascular health, but routine eating usually covers it.

# Practical recommendations

• Around big races or multi-hour efforts: consider a short course of higher-dose vitamin C (studies used 600 mg/day) in the days or week before to reduce post-race cold risk.

# Bottom line Vitamin C can cut post-race cold risk for runners undergoing heavy physical stress. It changes lab markers of stress but not how your muscles feel. Daily high doses can blunt mitochondrial adaptations and reduce endurance gains, so favor food-based intake during training and reserve short, targeted supplementation around key races if you struggle with post-race illness.