The common cold is often caused by the rhinovirus. It is one of the most widespread illnesses and is a leading cause of visits to the doctor and absence from school and work. Complications of the common cold include ear infection, sinusitis and exacerbations of reactive airway diseases. There is no proven treatment for the common cold. Zinc appears to interfere with the replication of rhinoviruses.
Zinc inhibits replication of the virus and has been tested in trials for treatment of the common cold. In 18 randomised controlled trials with 1781 participants of all age groups, zinc was compared with placebo (no zinc). Zinc (lozenges or syrup) reduces the average duration of the common cold in healthy people, when taken within 24 hours of onset of symptoms.
Zinc is a nutritionally essential mineral needed for catalytic, structural, and regulatory functions in the body.
The RDA (recommended daily allowance) for adult women and men is 8 mg a day and 11 mg a day of zinc, respectively.
Severe zinc deficiency is a rare, genetic or acquired condition. Dietary zinc deficiency, often called marginal zinc deficiency, is quite common in the developing world, affecting an estimated 2 billion people. Zinc deficiency can cause impaired growth and development in children, pregnancy complications, immune dysfunction, and increased susceptibility to infections. Long-term consumption of zinc in excess of the tolerable upper intake level of 40 mg a day for adults can result in copper deficiency.
Zinc bioavailability is relatively high in meat, eggs, and seafood. Zinc is less bioavailable from whole grains and legumes due to the inhibitory effects of phytic acid on absorption of the mineral.