In April 2018 researchers from Italy published the results of their review of the scientific literature to assess the preventative role of Vitamins C and D, zinc and Echinacea in the common cold. A total of 82 studies were identified. Results showed that regular vitamin C supplementation (1 to 2 g/day) reduced the duration (adults by 8%, children by 14%) and severity of the common cold. Zinc supplementation appeared to reduce the duration of colds by approximately 33% leading to the suggestion that individuals should try zinc within 24 hours of onset of cold symptoms. As for vitamin D, supplementation provided some protection against the common cold. However those individuals with vitamin D deficiency and those not receiving vitamin D supplements experienced the most benefit when starting supplementation. In addition, Echinacea supplementation (2400 mg/day) for longer than 4 months appeared to be beneficial for preventing/treating the common cold.
Rondanelli M et al. Self-Care for Common Colds: The Pivotal Role of Vitamin D, Vitamin C, Zinc, and Echinacea in Three Main Immune Interactive Clusters (Physical Barriers, Innate and Adaptive Immunity) Involved during an Episode of Common Colds-Practical Advice on Dosages and on the Time to Take These Nutrients/Botanicals in order to Prevent or Treat Common Colds. Evid Based Complement Alternat Med. 2018 Apr 29; [Epub ahead of print]