Vitamin C for Athletes: Does It Boost Performance?

observational-study PMID: 37417662

Quick Summary: A review of studies on vitamin C and athletic performance found mixed results. While some studies showed vitamin C might help reduce muscle damage after intense exercise, most found no significant improvements in performance. The review suggests getting antioxidants from food is better than relying on high-dose supplements.

What The Research Found

Researchers looked at 14 different studies to see if taking extra vitamin C helps athletes. Some studies showed that vitamin C might slightly reduce muscle soreness after hard workouts. However, most studies found that vitamin C didn't improve athletic performance, muscle soreness, or how well athletes adapted to training.

Study Details

Who was studied: Athletes of different types, including runners, cyclists, and people who lift weights.

How long: Studies lasted from a couple of weeks to about three months.

What they took: Athletes usually took at least 200mg of vitamin C per day, sometimes much more. Often, they also took vitamin E.

What This Means For You

If you're an athlete, this research suggests that taking high doses of vitamin C supplements might not be the best way to improve your performance. It's more important to eat a healthy diet rich in fruits and vegetables, which naturally contain vitamin C and other antioxidants. This is because your body needs to adapt to exercise, and too many antioxidants might interfere with that process.

Focus on food: Eat plenty of oranges, bell peppers, and other foods high in vitamin C.

Consider short-term use: If you're experiencing muscle soreness after a tough workout, a short course of vitamin C might offer some relief, but talk to your doctor first.

Skip the high doses: Long-term, high-dose vitamin C supplementation isn't recommended based on this research.

Study Limitations

It's important to remember that this research looked at many different studies, and they weren't all the same. Some studies used different amounts of vitamin C, and many also included vitamin E. This makes it hard to know exactly how vitamin C alone affects athletes. Also, the studies didn't always last very long, so we don't know the long-term effects.

Key Findings

The 2023 review analyzed 14 randomized controlled trials (RCTs) on high-dose vitamin C supplementation (≥200 mg/day) in athletes. Three studies reported statistically significant reductions in muscle damage markers (e.g., creatine kinase, lactate dehydrogenase) post-exercise, while 11 found no meaningful improvements in performance, muscle soreness, or training adaptations. The authors concluded that inconsistent data and potential interference with exercise-induced physiological adaptations do not support long-term high-dose vitamin C use, advocating for dietary intake instead.

Study Design

This observational study (systematic review) evaluated RCTs published over the past decade. It included 14 trials with varying populations: mixed genders, endurance athletes (runners, cyclists), and resistance-trained individuals. Study durations ranged from 2 weeks to 3 months. Methodological heterogeneity was noted, including differences in dosing, exercise protocols, and outcome measures.

Dosage & Administration

Most trials used ≥200 mg/day of vitamin C, with some administering ≥1,000 mg/day. Supplementation was typically combined with vitamin E (e.g., 400 IU/day), complicating isolation of vitamin C’s effects. Doses were delivered via capsules, powders, or fortified beverages, with administration timing varying (pre-, post-, or daily supplementation relative to exercise).

Results & Efficacy

Three RCTs found vitamin C reduced muscle damage markers by 15–30% (e.g., lower post-exercise creatine kinase levels; p < 0.05). However, 11 studies showed no significant effects on performance metrics (VO₂ max, time-to-exhaustion), perceived soreness (p > 0.05), or training adaptations (e.g., strength gains, endurance improvements). Co-supplementation with vitamin E in most trials may have confounded results, as antioxidant interactions were not systematically analyzed.

Limitations

The review’s observational design is limited by the heterogeneity of included RCTs (dosing, populations, exercise types). Most studies combined vitamin C with other supplements, obscuring its standalone efficacy. Short durations (≤3 months) hindered assessment of long-term impacts. Sample sizes were small (n = 10–50 per trial), and potential publication bias may exist. Future research should explore isolated vitamin C effects, optimal dosing, and sex-specific responses.

Clinical Relevance

Athletes should avoid long-term high-dose vitamin C supplementation due to inconsistent benefits and potential interference with training adaptations. The review supports obtaining antioxidants through whole foods (e.g., citrus fruits, bell peppers) rather than supplements. For acute muscle damage reduction, short-term use (≥200 mg/day) may show modest benefits, but individual variability and co-supplements like vitamin E complicate recommendations. Clinicians should prioritize dietary strategies