Zinc (Zn) is a catalyst necessary for activating about 100 enzymes involved in metabolic reactions within the cells. This mineral is necessary for the immune system, and zinc deficiency affects multiple aspects of innate and adaptive immunity. Zinc is very important for normal development and function of cells mediating nonspecific immunity such as neutrophils and NK (natural killer) cells.
Symptoms of Zinc Deficiency
The Symptoms of a moderate deficiency of zinc include growth retardation and male hypogonadism in adolescents, cell-mediated immune dysfunctions, delayed wound healing, poor appetite, rough skin and mental lethargy. The Symptoms of severe Zn deficiency in humans include alopecia, bullous pustular dermatitis, intercurrent infections due to cell-mediated immune dysfunctions, weight loss, hypogonadism in males, emotional disorder, neurosensory disorders, and problems with healing of ulcers. Clinical symptoms of Zn deficiency may occur when plasma zinc concentrations drop below 65 mcg/dL. Values less than 33 mcg/dL are especially associated with loss of the senses of taste and smell, diarrhea, abdominal pain, loss of appetite and skin rash.
Zinc and Immune Health
Zinc is known to play a critical role in the immune system, and zinc deficient individuals experience increased susceptibility to a variety of pathogens. Enough zinc intake is essential in maintaining the integrity of the immune system, specifically for normal development and function of cells that mediate both innate and adaptive immune responses. People with low Zn levels have shown reduced lymphocyte proliferation response to mitogens and other adverse alterations in immunity that can be corrected by zinc supplement. Zn deficiency in humans reduces the activity of serum thymulin, which is required for maturation of T-helper cells. Thymulin (a thymic hormone) is a thymus-specific hormone and it requires the presence of zinc for its biological activity to be expressed.
The found Zn has a important role in preventing too much inflammation, which could retard the body’s ability to fight infection. Professor Daren Knoell, lead researcher on the study, which is reported in the journal Cell Reports, said: “If you are deficient in zinc you are at a disadvantage because your defence system is amplified, and inappropriately so. “The effect to health is explicit; zinc is useful because it stops the action of a protein, ultimately preventing excess inflammation.” Certain aspects of immune function in the elderly have been found to improve with zinc. In a study in men and women over 65 years of age found that a zinc supplementation of 25 mg/day for 3 months increased levels of some circulating immune cells compared to placebo. In another study in 49 older participants (aged 55-87 years), 35% of which were considered zinc deficient, found that zinc supplement of 45 mg/day for twelve months reduced the incidence of infection and ex vivo markers of inflammation and oxidative stress.
Zinc and Common Cold Treatment
Clinical study findings support the value of zinc in reducing the duration and severity of symptoms of the common cold when administered within 24 hours of the onset of common cold symptoms. Zn has been shown, in some studies, to inhibit the reproduction of viruses and may promote the production of the virus-fighter interferon. Most colds are caused by a type of virus called rhinovirus, which thrives and multiplies in the nasal passages and throat. Rhinoviruses belong to the same virus family as the more widely feared poliovirus. Human rhinoviruses, by attaching to the nasal epithelium via the intracellular adhesion molecule-1 receptor, cause most colds. Rhinovirus is very effective at producing infections. It has been shown that 95% of individuals exposed to a rhinovirus strain they have not previously encountered become infected, and 75% of those infected become ill. Laboratory study has shown that the zinc is known to help block replication of rhinoviruses and other viruses which affect the respiratory system.
According to a study, reported in the Oct 2004 edition Journal of American Pharmacist Association, zinc helps decrease the duration and severity of symptoms of the common cold. Researchers think that zinc lozenges or nasal sprays may avoid the virus that causes the common cold from attaching to the nasal cavities, windpipe, and lungs. In lab experiments, this mineral interacts with the virus’ “coat” and changes its ability to assemble into mature virus particles. In a clinical study, 50 participants took a zinc acetate lozenge (13.3 mg zinc) or placebo every 2–3 wakeful hours. Compared with placebo, the zinc lozenges significantly reduces the duration of cold symptoms. In another study involving 273 subjects with experimentally induced colds, zinc gluconate lozenges (13.3 mg zinc) significantly reduced the duration of illness compared with placebo. In a study looked at the ability of zinc lozenges to treat the common cold in adults. Within 24 hours of experiencing cold symptoms, 99 participants took zinc or placebo lozenges every 2 hours. At the end of the study, participants taking zinc lozenges had their cold symptoms for just 4.4 days, on average, while participants taking the placebo had theirs for an average of 7.6 days.
Depending on the total dosage of zinc and the composition of lozenges, zinc lozenges may shorten the duration of common cold episodes by up to 40%, according to a study reported in the “Open Respiratory Medicine Journal“. A review of the available scientific findings show taking zinc within a day of the onset of cold symptoms speeds recovery. Furthermore, it may help ward off colds, explain the authors of the Cochrane Systematic Review that included data from 15 trials involving 1360 people. According to the Cochrane Review, when taken within 24 hours of the first symptoms of a cold zinc lozenges, syrups or capsules, can cut colds short by several days and sharply reduce the severity of symptoms.