A new review1 of 82 existing studies on vitamins C and D, zinc, and echinacea (Echinacea purpurea) adds further support to those nutrients’ ability to help maintain immune health and reduce the severity and duration of cold symptoms. The review, which was published in the journal Evidence-Based Complementary and Alternative Medicine, found that vitamin C, vitamin D, zinc, and echinacea can help boost immune-system barriers often involved in fighting the common cold, including physical barriers, innate immunity, and adaptive immunity. The review also provides advice on the best dosage amounts and the ideal time and duration to supplement with vitamin C, vitamin D, zinc, and echinacea in order to reduce cold symptoms.
The study authors wrote that maintaining a healthy immune defense system lowers the severity of common cold symptoms, as well as the duration of a cold episode. In this review, the researchers sought specifically to determine the efficacy of supplementation with vitamins C and D, zinc, and echinacea on three main immune-health interactive clusters: physical barriers, innate immunity, and adaptive immunity. Physical barriers, they wrote, include a low pH caused by various fatty acids and enzymes, which can limit bacteria growth; mucus secretion; and the acidity of the stomach. Innate immunity refers to the immune system cells, such as NK cells, cytokines, macrophages, and neutrophil granulocytes. The third barrier, adaptive immunity, is acquired later in life—for example, after an immunization—and involves lymphocytes T and B.
Upon reviewing the existing data, the researchers found that regular vitamin C supplementation (1 g to 2 g/day) reduces the duration and severity of common cold symptoms by 8% in adults and by 14% in children. Zinc was found to shorter the duration of colds by roughly 33%, but the authors also point out that subjects may be instructed to consume zinc within 24 hours after the onset of cold symptoms. Vitamin D, meanwhile, protected against the common cold. In the studies analyzed in the current review, patients with a deficiency in vitamin D experienced the most significant immune-health benefits from vitamin D supplementation. Subjects who supplemented with echinacea (2400 mg/day for prevention and 4000 mg/day during acute stages of colds) over a period of four months appeared to have fewer occurrences of cold symptoms.
All of the nutrients included in this review, “have pivotal roles of three main immunoreactive clusters (physical barriers, innate, and adaptive immunity) in terms of prevention and treatment (shortening the duration and/or lessening the severity of symptoms) of common colds,” wrote the study authors. They concluded that the current review adequately demonstrated that vitamin C, vitamin D, zinc, and echinacea can be effective way to attenuate symptoms of the common cold, and to boost immune health.
1. 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,” Evidence-Based Complementary and Alternative Medicine. Published online April 29, 2018.