Can extra vitamin C help treat a cold?<\/p>\n
Vitamin C has been sold as a cold remedy for decades, but a review of 29 studies<\/a> found no convincing evidence that taking vitamin C supplements regularly prevents colds.<\/p>\n There is some evidence that it might slightly reduce the duration of a cold, but only by around 8%. So for a cold that lasts a week, that\u2019s around half a day.<\/p>\n People who seemed to benefit more from supplements were those under extreme physical stress, like marathon runners or those training in cold temperatures. In these cases, taking a vitamin C supplement two to three weeks before the intense training exercise reduced the risk of developing a cold by half.<\/p>\n Taking more than 1,000mg (one gram) a day of vitamin C has been linked with diarrhoea and stomach cramps. At doses above one gram, absorption also falls to less than 50%, and anything your body doesn\u2019t absorb is flushed out in urine, so mega doses offer little benefit.<\/p>\n Originally published October 2025<\/p>\n Laura Tilt is a registered dietitian with a master\u2019s in public health nutrition and a postgraduate diploma in dietetics. Since qualifying in 2012, she has specialised in gastroenterology at London\u2019s UCLH before moving into freelance practice. With over 10 years of experience translating nutrition science into accessible, meaningful advice, Laura\u2019s specialist interests include digestive health, disordered eating, and sports nutrition.<\/p>\n Want more? Visit BBC Food on Instagram<\/a>, Facebook<\/a> and Pinterest<\/a> or watch the latest Food TV programmes on BBC iPlayer<\/a>.<\/p>\n