Zinc may reduce the severity and length of a cold. Fifty subjects received either zinc lozenges (containing 13.3 mg of zinc acetate) or a placebo at the onset of a cold, according to research published in the Journal of Infectious Disease (2008 March 15;197(6):795-802). The group receiving the supplement had cold symptoms for less time than the placebo group; with the placebo group being symptomatic for over seven days and the supplement group having symptoms for only four days. The zinc supplementation also reduced serum biomarkers indicating inflammation from the cold.

Research appearing in the American Journal of Medicine (1999;106:138-143) looked at the effect Echinacea purpurea had on the common cold. The 109 subjects of the study were given either 4 ml of Echinacea extract or a placebo twice each day for eight weeks. Fewer of the group receiving the Echinacea had a cold or respiratory infection during the course of the study (65% in the Echinacea group vs 75% in the placebo group). The duration of the respiratory infections were less in the group receiving the herb, lasting 4.5 days, compared to 6.5 days for the placebo group.

There is some evidence that vitamin C can help to prevent or alleviate colds. In research appearing in the Journal of Manipulative and Physiologic Therapeutics (1999;22(8):530-533), 463 students with colds were treated with either 1,000 mg of vitamin C (hourly for the first six hours, then three times per day thereafter) or decongestants and pain medication. The group receiving the vitamin C had an 85% reduction in symptoms compared to the control group. Other research appearing in the European Journal of Clinical Nutrition (2006; 60(1): 9-17) found that supplementation with vitamin C over a period of five years reduced the frequency of the common cold. The 244 subjects were given 50 mg of vitamin C per day or 500 mg of vitamin C per day. The group receiving the 50 mg dose had a total number of 21.3 common colds (per 1000 person-months). The group receiving the higher dose had 17.1 common colds per 1000 person-months.