Elderberry for the Flu
There's some promising evidence that elderberry might help treat the flu, Leopold says. Elderberry appears to boost the production of some immune cells and may also help block a virus's ability to spread. One study shows that taking 4 tablespoons a day for three days of a specific formulation of elderberry extract -- Sambucol -- appears to shorten the symptoms of flu by 56%. It also seems to reduce some flu symptoms, like fever. However, the study was small and the full implications aren't clear.
Garlic for Colds and Immunity
Like a number of other supplements, garlic seems to stimulate the immune system. Garlic may also help fight viruses. Also, there is some preliminary evidence that garlic may lower the risk of catching a cold. Garlic works best when consumed raw, either crushed, diced, or minced. Overcooking garlic may destroy important medicinal compounds and the enzymes necessary for it to be effective.
However, more research needs to be done. Note: Garlic may be dangerous in people taking blood thinners.
Ginseng for Cold and Flu
Although commonly used as a mild stimulant, the different ginseng species may also boost the immune system and help prevent or treat cold and flu. One species, panax ginseng, may also increase the protection offered by the flu vaccine.
Coates singles out a specific blend of North American ginseng sold as Cold fX. Preliminary results suggest that Cold fX, when taken for several months during flu season, seems to lower the risk of contracting either cold or flu. One study looked at Cold fx as a treatment, and found that it reduced the duration and severity of symptoms. "The jury's still out, but the evidence is promising," says Coates.
Andrographis for Colds and Immunity
"Andrographis is called 'Indian echinacea,'" says Evangeline Lausier, MD, assistant clinical professor at Duke Integrative Medicine in Durham, N.C. "It seems to stimulate the immune system." Studies of andrographis show that it appears to improve cold symptoms significantly, at least when started within three days of the onset. There's also some early evidence that it may reduce the chances of catching a cold, at least when taken for several months beforehand. Most studies have used a specific product called Kan Jang, which combines andrographis with Siberian ginseng (eleutherococcus senticosus).
Combination Supplements for Colds and Flu
Many alternative medicines packaged for cold and flu are combinations of some of the herbs and vitamins listed above -- typically echinacea, zinc, high doses of vitamin C, and other ingredients. Although there's no particular reason to think that combination cold and flu products are more dangerous, they're much less likely to have been studied than the individual ingredients that they contain. You might be better off choosing the specific supplements in the dosages you want.
These aren't the only supplements sold as natural cold and flu remedies. Others include astragalus, goldenseal, kiwi, boneset, and homeopathic oscillococcinium. However, so far, there's not enough evidence to say whether they help with cold or flu.