Vitamin C has long been linked to the prevention of colds, a belief popularized over 50 years ago by Linus Pauling, a Nobel Prize-winning chemist and peace activist. Pauling recommended high daily doses of vitamin C—between 1,000 and 2,000 milligrams—based on early studies, including one conducted in a ski camp in the Swiss Alps. However, his conclusions have since been criticized for relying on low-quality research and flawed data analysis. While vitamin C does not prevent most people from catching a cold, recent studies suggest it may slightly reduce the severity and duration of symptoms for some individuals. A 2023 meta-analysis, which combined data from ten placebo-controlled trials involving 2,736 healthy adults, children, and athletes, found that people who regularly took at least 1,000mg of vitamin C daily experienced a 15% reduction in severe cold symptoms. This was measured by the number of days they were "confined indoors," though the researchers noted this metric as a limitation. The study also found no effect on the duration of mild symptoms. However, the benefits were not consistent across all groups, and the results should be interpreted cautiously. Earlier research, including a 2013 meta-analysis, found that taking lower doses of vitamin C (around 200mg a day) did not reduce the number of colds in the general population. However, it did show a decrease in cold frequency among athletes and military personnel. Regular vitamin C supplementation was linked to a reduction in symptom severity by 8–14% in both children and adults. However, taking vitamin C only when a cold has already started had no effect on symptoms. Linus Pauling’s original advice is now considered overstated, as there is no solid evidence that vitamin C reduces the risk of catching a cold. There is some evidence it may reduce the duration of severe symptoms by about 10% on average. However, any benefit is only seen when vitamin C is taken regularly, even before symptoms appear. Pauling’s recommended dose of 1,000–2,000mg a day is near the upper limit of what is currently considered safe. In the United States, the recommended maximum intake is 2,000mg per day, while in Australia, the daily requirement for adults over 19 is just 45mg. High doses of vitamin C can cause side effects such as gastrointestinal discomfort, increased oxalate excretion (which may lead to kidney stones), and excessive iron absorption, which can be harmful to people with undiagnosed hemochromatosis. It can also interact with certain medications, including chemotherapy, radiation therapy, and statins. Before taking vitamin C supplements, it is advised to consult a general practitioner and keep the dose below 1,000mg per day. In Australia, less than 4% of the population is deficient in vitamin C.