Zinc is a critical player for optimum functioning of the immune system. In particular, zinc has long been hailed for its ability to speed recovery from the common cold. This belief came from a study in the mid-80s in which zinc gluconate lozenges were tested. Since then, numerous studies have been conducted, with results showing either moderate or no effectiveness in reducing the severity and duration of colds.

However, in a recent study using zinc acetate, lozenges were shown to taste "identical" to placebo and produce a significant reduction in the duration and severity of colds. The average daily dose was 80 mg of zinc for four to five days. Because zinc lozenges can produce side effects (nausea, metallic aftertaste and diarrhea) use of an intranasal zinc (Zicam) homeopathic gel has also been studied. In the first study, subjects with naturally acquired colds who used Zicam showed a marked reduction in the severity and duration of cold symptoms and effects.

In a more rigorous recent study, subjects were "challenged" with a specific cold virus (rhinovirus) and no improvement in symptom scores was found. Any effect of zinc on colds was not connected to food but was connected to supplements.

Nutrition and exercise biochemist Anthony Almada, MS, has collaborated on more than 45 university-based studies. He is cofounder of Experimental and Applied Sciences (EAS) and founder and chief scientific officer of IMAGINutrition.