Silver science
Silver was the antimicrobial of choice before the introduction of antibiotics (Surg Infect [Larchmt], 2009; 10: 289-92). However, when it comes to the colloidal silver products on the market today-usually meant to be taken by mouth-there’s little evidence to support their efficacy.
Colloidal silver reportedly acts as a catalyst, disabling the enzyme that all one-celled bacteria, viruses and fungi need to metabolize oxygen. This done, they suffocate-and supposedly with no harm to human enzymes and other working parts of the body’s chemistry. Few conventional drugs can claim to be so finely targeted.
Some test-tube studies suggest that colloidal silver is a powerful antimic-robial agent. In one, colloidal silver solutions with a silver concentration of 30 ppm (parts per million) or higher were able to kill the Staphylococcus aureus bacteria that cause a range of conditions, from acne to pneumonia (Med Eng Phys, 2008; 30: 948-52). In another, researchers in India and the US tested a liquid silver solution together with 19 antibiotics against seven bacterial strains, but excluding those that were resistant. Out of 96 tests, the combination was effective in all but two (Curr Sci, 2006; 91: 926-9).
However, a study to test the efficacy of three colloidal silver preparations-one available via the Internet (silver concentration of 22 ppm) and two
that were specially prepared in the lab (concentrations of 403 and 413 ppm)-reported that none were found to have any antimicrobial effects (J Wound Care, 2004; 13: 154-5).
What’s more, there’s little research in humans. Even if colloidal silver can
kill bacteria and other microbes in a test tube, that’s no guarantee that the results will be the same in people. Also, to our knowledge, there are no clinical studies showing that colloidal silver is effective against any specific health conditions.
Of the published studies that can be found, most are single-patient reports of adverse effects as a result of taking colloidal silver. These reports describe cases where using colloidal silver led to argyria, characterized by a bluish-gray discoloration of the skin that is neither treatable nor reversible. Although the actual dosage necessary to produce this condition is not known, argyria has been associated with both long-term supplementation (one to two years) (Int J Dermatol, 2003;
42: 549) and extremely high doses (1 L/ day) (Am J Ind Med, 2009; 52: 246-50).
High doses of colloidal silver have also been found to lead to vomiting, diarrhoea, seizures, coma and even death (Dermatol Online J, 2005; 11: 12; Neurology, 2004; 62: 1408-10).
Silver speculation
According to some reports, much of the danger surrounding colloidal silver is related to the fact that we don’t know exactly how much silver is in
the solution or the size of the silver particles. Even though the product labelling may seem clear, the term ‘ppm’ does not refer to the number of particles in the solution, but to their weight. Silver particles can range from 0.005 to 0.015 microns in diameter, and the smaller the diameter, the greater the number of particles (and weight). This means that a product with a concentration of 5 ppm with an average particle size of 0.005 microns will contain more silver particles than a product of 25 ppm with an average size of 0.015 microns.
So, despite the fact that the US Environmental Protection Agency has established a non-lethal oral reference dose for silver (5 mcg/kg body weight), it may be difficult to know if you’re exceeding this level or not.
Ultimately, while the manufacturers of colloidal silver insist that their products are safe and effective, until more research is carried out-or the labelling becomes more informative-we just don’t know if this is true.
Joanna Evans
Promising silver studies
While there’s little evidence to support the use of oral colloidal silver, a number of studies suggest that silver compounds applied topically may be a useful treatment for burns and other wounds. In fact, silver sulphadiazine-a topical cream combining silver nitrate with a sulphonamide antibiotic-has been used to manage burns-related infections for the past 40 years, although recent findings suggest the cream may also be delaying wound healing and may even have serious cell-killing actions (Burns, 2007; 33: 139-48).
Lately, silver-impregnated dressings have gained popularity, mainly due to the increase of antibiotic-resistant bacteria. Silver has proven antibacterial activity in the lab against a wide range of bacteria, including antibiotic-resistant strains (Am J Nurs, 2006; 106: 60-8). In human trials, silver-releasing dressings generally show “positive effects” on chronically infected wounds. However, high-quality evidence is still lacking (J Clin Nurs, 2008; 17: 1973-85).
WDDTY Volume 20 Issue 10
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