Vitamin C Won’t Prevent Colds, But May Lightly Ease Severe Symptoms in Some People
Regular vitamin C does not reduce the risk of catching a cold, but meta-analyses suggest a modest benefit for those who take it consistently: about 8–14% less severe symptoms in children and adults, and roughly a 15% reduction in days with severe symptoms among groups like athletes and military personnel. Starting vitamin C after symptoms begin provides no benefit. High daily doses (>1,000 mg) can cause GI problems, kidney stones, and drug interactions; upper limits vary by country (US ~2,000 mg; Australia ~1,000 mg), while typical daily needs are far lower (Australia ~45 mg). Since deficiency is rare, most people don’t need supplements—consult a GP if considering it.
