The onset of cold and flu season serves as a reminder of the critical importance of maintaining adequate stores of the mineral zinc.
While best known for its role in fighting colds and flus, zinc has far-ranging effects on human health, from strengthening the body’s immune defenses to promoting optimal growth and development.1 The tenth most common element in the human body, zinc is vital to the functioning of more than 300 hormones and enzymes.2 One of the most important of these is copper/zinc superoxide dismutase, an antioxidant enzyme associated with longevity and protection against oxidative stress.3-5
Zinc deficiency is associated with numerous disease states and even with DNA damage, which may contribute to cancer.6 With a preponderance of scientific evidence suggesting that zinc deficiency is common in the United States and throughout the world, it is all the more important that health-conscious adults take steps to ensure optimal zinc status.
Boosting the Body’s Antioxidant Defenses
Zinc is an essential component of one of the body’s most important natural antioxidants, the enzyme known as copper/zinc superoxide dismutase (Cu/Zn SOD).3,4 Cu/Zn SOD is one of a family of antioxidant enzymes that disarm dangerous superoxide radicals, which can wreak havoc on cellular compounds such as lipids, proteins, and DNA.5,7 Cu/Zn SOD rapidly breaks these compounds down into hydrogen peroxide, which is quickly converted to harmless water and ordinary oxygen.8
Research suggests that maintaining adequate levels of zinc and SOD is especially important to increasing longevity. Cumulative oxidative damage caused by reactive oxygen species is correlated with aging. In the laboratory, organisms that were manipulated to produce higher levels of SOD demonstrated extended life spans.5 Conversely, mutations in the gene that encodes Cu/Zn SOD have been associated with familial amyotrophic lateral sclerosis (Lou Gehrig’s disease), a fatal neurodegenerative disorder.7 Oxidative damage to the enzyme itself has recently been implicated in a variety of pathologies, including Alzheimer’s and Parkinson’s diseases.9
Oral supplementation with a bioavailable SOD preparation provides a way to greatly augment the protective benefits conferred by the body’s own supply of superoxide dismutase.10
A Cornerstone of Healthy Immune Function
In addition to bolstering the body’s antioxidant defenses, zinc plays a crucial role in supporting proper immune system function.11-15 T-lymphocytes are white blood cells that help fight infection and depend on zinc for their development and activation. In humans, zinc deficiency can result in a decreased number of T-lymphocytes and a diminished ability to fight infection and heal wounds.16-18 Because supplemental zinc may help fight infection and heal wounds,17 zinc status is especially important for patients with conditions such as HIV infection.18
Maintaining adequate levels of zinc is equally important to aging adults. As people grow older, their immune function declines, partly due to the decreasing size and function of the thymus gland. New evidence suggests that zinc may help to maintain healthy function of the thymus gland in elderly people.19 Scientists have also found evidence that a zinc deficiency in elderly adults may contribute to impaired immune function with aging, or immunosenescence.20 These findings suggest that zinc plays a critical role in supporting healthy immune function with age.
Zinc Fights Symptoms of the Common Cold
One of zinc’s most important uses in recent years is reducing the severity and duration of colds. The common cold is caused by any one of more than 200 distinct viruses that target the respiratory tract.23 Zinc interferes with the viruses’ ability to attach to the surface of respiratory tract cells and reproduce, which may help prevent infections from taking hold and causing symptoms.24
Numerous clinical trials, involving hundreds of child and adult patients, support the effectiveness of zinc lozenges in mitigating cold symptoms.23-29 One study concluded that lozenge use within 24 hours of the first onset of cold symptoms reduces the severity of symptoms, the duration of the illness, subsequent use of antibiotics to treat secondary symptoms, and overall incidence of colds per year.29
Colds can also lead to even more serious secondary conditions, such as sinusitis in adults and middle ear infections in children. Indeed, acute upper-respiratory infection is the single most common reason people seek medical treatment in the United States.25 Vanderbilt University scientists discovered that zinc inhibits the activity of a common respiratory virus that routinely threatens children’s health. The doctors added zinc salts, such as zinc sulfate and zinc lactate, to cell cultures infected with a common pediatric respiratory disease known as respiratory syncytial virus. Zinc salts prevented the harmful virus from replicating freely.30
To be most effective, zinc lozenges should be taken within 24 hours of the appearance of initial cold symptoms, and should be taken continuously throughout the course of the illness. Although generally well tolerated, some patients have reported mild nausea when taking zinc lozenges, and temporary alterations in taste sensation are not uncommon. Taking zinc with food may help to alleviate these effects.
Supporting Human Growth and Maturation
Zinc is vital to human growth and maturation. Studies have shown that zinc deficiency results in cognitive deficits and growth retardation, including delays in sexual maturation, among both males and females.36-39 Scientists in California report that even moderate zinc deficiency results in disruptions in normal growth and maturation among rhesus monkeys, and behavioral changes, including lethargy, may precede physical manifestations of deficiency.40,41 The same appears to hold true for humans. Zinc deficiency is linked to deficits in healthy bone mineralization, and has been linked to short stature and developmental delays.36-39
According to researchers in California who conducted a meta-analysis of clinical trials examining the effects of zinc supplementation on children’s growth, “Zinc supplementation produced highly significant, positive responses in height and weight increments.”42 Researchers in Turkey recently reported that zinc supplementation stimulates the production of insulin-like growth factor 1 (IGF-1) and other proteins and polypeptides involved in bone and overall growth.43 IGF-1 responds directly to growth hormone and is responsible for regulating the growth and development of a wide range of cells, as well as DNA synthesis.
Zinc also plays a key role in spermatogenesis, the process by which the male testes produce sperm capable of fertilizing an egg, or ovum. Numerous studies comparing fertile and infertile men have demonstrated that zinc is abnormally low in the blood serum and seminal fluid of infertile men.44-47 Replenishing zinc levels may thus be helpful in optimizing male fertility.