Many herbal and otherwise alternative remedies have been suggested to treat the common cold. However, none of these claims are supported by scientific evidence.^[1]

Contents 1 Echinacea 2 Vitamin C 3 Zinc preparations 4 Steam inhalation 5 Chicken soup 6 References

[edit] Echinacea

Echinacea, also known as coneflowers, is a plant commonly used in herbal preparations for the treatment of the common cold.

Although there have been scientific studies evaluating echinacea, its effectiveness has not been convincingly demonstrated. For example, a peer-reviewed clinical study published in the New England Journal of Medicine concluded that "…extracts of E. angustifolia root, either alone or in combination, do not have clinically significant effects on rhinovirus infection or on the clinical illness that results from it."^[2][3] Recent randomized, double-blind, placebo-controlled studies in adults have not shown a beneficial effect of echinacea on symptom severity or duration of the cold.^[4][5] A structured review of 9 placebo controlled studies suggested that the effectiveness of echinacea in the treatment of colds has not been established.^[6] Conversely, two recent meta-analyses of published medical articles concluded that there is some evidence that echinacea may reduce either the duration or severity of the common cold, but results are not fully consistent. However, there have been no large, randomized placebo-controlled clinical studies that definitively demonstrate either prophylaxis or therapeutic effects in adults.^[7][8] A randomized, double-blind, placebo-controlled study in 407 children of ages ranging from 2 to 11 years showed that echinacea did not reduce the duration of the cold, nor reduce the severity of the symptoms.^[9] Most authoritative sources consider the effect of echinacea on the cold unsupported by evidence.^{[10][11][1][12][13][14]}

[edit] Vitamin C

A well-known supporter of the theory that Vitamin C megadosage prevented infection was physical chemist Linus Pauling,^[15] who wrote the bestseller Vitamin C and the Common Cold.^[16] A meta-analysis published in 2005 found that "the lack of effect of prophylactic vitamin C supplementation on the incidence of common cold in normal populations throws doubt on the utility of this wide practice".^[17]

A follow-up meta-analysis supported these conclusions:

[Prophylactic use] of vitamin C has no effect on common cold incidence ... [but] reduces the duration and severity of common cold symptoms slightly, although the magnitude of the effect was so small its clinical usefulness is doubtful. Therapeutic trials of high doses of vitamin C ... starting after the onset of symptoms, showed no consistent effect on either duration or severity of symptoms. ... More therapeutic trials are necessary to settle the question, especially in children who have not entered these trials.^[18][19]

Most of the studies showing little or no effect employ doses of ascorbate such as 100 mg to 500 mg per day, considered "small" by vitamin C advocates.^[who?] Equally important, the plasma half life of high dose ascorbate above the baseline, controlled by renal resorption, is approximately 30 minutes,^[20][21] which implies that most high dose studies have been methodologically defective and would be expected to show a minimum benefit.^{[citation needed]} Clinical studies of divided dose supplementation, predicted on pharmacological grounds to be effective, have only rarely been reported in the literature.^{[citation needed]}

[edit] Zinc preparations

Zinc acetate and zinc gluconate have been tested as potential treatments for the common cold, in various dosage form including nasal sprays, nasal gels, and lozenges.^[22][23] Some studies have shown some effect of zinc preparations on the duration of the common cold, but conclusions are diverse.^[24][25][26] About half of studies demonstrate efficacy. Even studies that show clinical effect have not demonstrated the mechanism of action.^[27] The studies differ in the salt used, concentration of the salt, dosage form, and formulation, and some suffer from defects in design or methods. For example, there is evidence that the potential efficacy of zinc gluconate lozenges may be affected by other food acids (citric acid, ascorbic acid and glycine) present in the lozenge.^[28] Furthermore, interpretation of the results depends on whether concentration of total zinc or ionic zinc is considered.^[29][30]

A recent study showed that zinc acetate lozenges (13.3 mg zinc) shortened the duration and reduced the severity of common colds compared to placebo in a placebo-controlled, double blind clinical trial. Intracellular Adhesion Molecule-1 (ICAM-1) was inhibited by the ionic zinc present in the active lozenges, and the difference was statistically significant between the groups. ^[31]

There are concerns regarding the safety of long-term use of cold preparations in an estimated 25 million persons who are haemochromatosis heterozygotes.^[32] Use of high doses of zinc for more than two weeks may cause copper depletion, which leads to anemia.^[33] Other adverse events of high doses of zinc include nausea, vomiting gastrointestinal discomfort, headache, drowsiness, unpleasant taste, taste distortion, abdominal cramping, and diarrhea.^[27][33] Some users of nasal spray applicators containing zinc have reported temporary or permanent loss of sense of smell.^[34]

Although widely available and advertised in the United States as dietary supplements or homeopathic treatments, the safety and efficacy of zinc preparations have not been evaluated or approved by the Food and Drug Administration. Authoritative sources consider the effect of zinc preparations on the cold unproven.^[1][12]

[edit] Steam inhalation

Many people believe that steam inhalation reduces symptoms of the cold.^[35] However, one double-blind, placebo-controlled, randomized study found no effect of steam inhalation on cold symptoms.^[36] A scientific review of medical literature concluded that "there is insufficient evidence to support the use of steam inhalation as a treatment."^[37] There have been reports of children being badly burned when using steam inhalation to alleviate cold symptoms leading to the recommendation to "...start discouraging patients from using this form of home remedy, as there appears to be no significant benefit from steam inhalation."^[38]

[edit] Chicken soup

In the twelfth century, Moses Maimonides wrote, "Chicken soup...is recommended as an excellent food as well as medication."^[39] Since then, there have been numerous reports in the United States that chicken soup alleviates the symptoms of the common cold. Even usually staid medical journals have published tongue-in-cheek humorous articles on the alleged medicinal properties of chicken soup.^[40][41][42]

[edit] References