Critics of alternative medicine frequently decry the use of herbs and other supplements for treating colds and influenza. For example, Marilynn Marchione, a medical journalist for the Associated Press, contends that the National Center for Complementary and Alternative Medicine (NCCAM) has spent around $2.5 billion on research over the past decade and has “found no cures from alternative medicine.”
These same pundits cite the powerful placebo effect that is associated with alternative remedies, but they fail to emphasize that the placebo effect also plays a prominent role in treatments offered by mainstream medicine… including prescription drugs.
Alternative medicine’s advocates argue that today’s “evidence-based” methodology – the same process that brought Vioxx, Rezulin, Fen-phen, and similar medical debacles to the American market – is inadequate for studying alternative therapies, many of which are supported by millennia of empirical evidence.
So, notwithstanding the opinions of self-proclaimed experts, it is worth examining the science that attests to the benefits of several popular alternative cold and flu remedies.
Echinacea
In 2003, a NCCAM study showed that Echinacea failed to prevent or shorten the course of common colds. The scientists who conducted this trial utilized the plant’s flowers for their investigation; traditional herbalists usually use the root or leaves, which contain higher concentrations of important constituents.
A 2007 meta-analysis of 14 studies showed that adults who took Echinacea purpurea decreased the incidence of colds by 58% and decreased a cold’s duration by 1.4 days. Likewise, a 2006 Cochrane review of 16 studies demonstrated that Echinacea was more effective than placebo for treating colds.
Echinacea has not been well-studied for use in influenza; since the herb’s impact on cytokine production in the human body is unclear, its use in H1N1 (which may induce a cytokine storm) is not currently recommended.
Studies demonstrating Echinacea’s benefits usually employed high-quality preparations; unfortunately, products sold in the U.S. vary substantially in quality.
Ginseng
Randomized clinical trials have shown that a standardized preparation of ginseng (Panax quinquefolium), taken on a daily basis for several months, can significantly reduce the incidence (by 25%) and duration (by about six days) of colds in adults.
Likewise, an Italian study showed that P. ginseng, when compared with placebo, boosted antibody levels and increased natural killer cell activity following influenza immunization.
Elderberry
To date, no studies have shown that black elderberry extracts (Sambucus nigra) are effective for preventing or treating colds.
However, several studies from Norway and Israel suggest that elderberry inhibits the growth of influenza viruses in tissue culture and shortens the duration of influenza symptoms while increasing viral antibodies.
Garlic
Garlic is a popular folk remedy for treating colds and flu, and at least one well-designed study revealed that a daily garlic supplement (180 mg allicin content) taken for three months reduced the incidence of common colds.
Randomized clinical trials have not evaluated garlic’s effectiveness for preventing or treating influenza.
Vitamins and Minerals
Although many vitamins and minerals have putative roles in preventing viral illnesses, vitamin C, vitamin D, and zinc have been extensively studied.
- Vitamin C has long been touted for preventing and alleviating upper respiratory tract illnesses (URTIs) and influenza. One Cochrane review of 30 trials involving over 10,000 subjects showed that vitamin C supplementation did not reduce the incidence of colds in most healthy adults, but a subgroup of subjects who engaged in strenuous physical activity experienced a 50% reduction in URTIs. Vitamin C taken as a preventive reduced the duration of colds in both adults and children, but supplementing after a cold’s onset conferred no significant benefit.
- Vitamin D boosts innate immunity and modulates inflammation. Analysis of NHANES data gathered between 1988 and 1994 reveals an inverse relationship between serum vitamin D levels and the incidence of colds.
- Zinc plays a pivotal role in immune function, and zinc supplementation has been shown to decrease the incidence of childhood pneumonia in developing countries. However, in recent trials, the evidence for zinc’s benefits in preventing or treating colds and flu has been mixed. Studies showing benefit involved the use of zinc lozenges that did not contain citric or tartaric acid, and treatment was started shortly after symptom onset.
Other Preparations
Other cold remedies that may not be well known to many people have found support in the scientific literature, while others have not yet proven themselves beneficial:
- Andrographis (an Ayurvedic remedy) and Pelargonium, herbs that aren’t familiar to most Americans, have proven beneficial for alleviating the symptoms of both colds and influenza. Notably, a 2003 Russian study showed that Andrographis compared favorably to amantadine for the treatment of influenza A.
- Studies evaluating the effectiveness of probiotics (bacteria that are normal inhabitants of the human gut) have produced mixed results. However, specific strains of organisms (certain species of Lactobacillus and Propionibacterium, for example) have shown consistent results in reducing the incidence of URTIs and flu-like illnesses and in decreasing the use of antibiotics in study participants.
- Although several homeopathic remedies are marketed for colds and flu, no controlled studies to date have demonstrated significant benefit from the use of homeopathic products for these conditions.
It appears that there is sufficient evidence of benefit from some alternative remedies to consider their use for preventing or treating colds or flu. Opponents of complementary medicine may be mistaken in their assumption that research shows no clear evidence to support alternative approaches; rather, it appears that sufficient research just hasn’t been done.
Sources:
Kemper K. Complementary and alternative medicine therapies for cold and flu Season: what is the science? Medscape Today (from WebMD). November 3, 2009
Marilynn Marchione. $2.5 billion spent, but no alternative medicine cures found yet. Associated Press. June 11, 2009)
Stephen Allen Christensen - Dr. Steve Christensen's writing has appeared in magazines, professional journals, poetry anthologies, and children's books since 1976.
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