What can you do right now to prevent getting the flu? As H7N9 continues to dominate our health headlines, I thought I’d continue my refresher course on prevention of this and other viruses. I’ve already discussed the specific tips for preventing H7N9 bird flu as well as getting a good night’s sleep; now let’s go over the actual evidence for the many herbal and non-prescription methods to prevent colds and flu. With herbal treatments, my favorite source is always from the Natural Medicines Database. They have an outstanding free article researching the best evidence for every common herb that people use to fight colds and flu. They also have a terrific graph at the end which summarizes the data. Here is a screenshot:

As you can see, there is nothing in their green zone of therapies proven “likely safe and effective”. Their highest level is American ginseng, listed as “possibly safe and effective”. Then we have a slew in the “insufficient evidence” pile including ALA, garlic, lactobacillus and others. You will probably be surprised to find that the most commonly used preventive medicines such as echinacea, vitamin C and zinc all are considered “possibly ineffective”, lower than many other herbals. You’re welcome to disagree, but they always back up their findings from a continuing review of the latest research. Here is a snippet of their details:

Echinacea is widely used to prevent upper respiratory infections including colds and flu. In vitro research suggests that echinacea stimulates the immune system, causing macrophages to produce tumor necrosis factor, interleukin-1, and beta-interferon.^6388,6389 Echinacea has been studied for prophylaxis against the common cold, but has consistently been shown to be ineffective.^{3281,3282,6386,6417,8228,10782,12354,13419,14419} Don’t recommend echinacea for PREVENTING colds and flu.

American ginseng might also be beneficial. Some evidence suggests that taking a specific American ginseng extract called CVT-E002 (Cold fX, Afexa Life Sciences, Canada) 200 mg twice daily over a 3-4 month period during influenza season might decrease the risk of developing symptoms of an upper respiratory tract infection such as the common cold or flu in adults aged 18-65 and older.^{11351,13192,14345} It might not reduce the chance of getting the first cold of a season, but might reduce the risk of getting repeat colds in a season.¹³¹⁹² When respiratory infections do occur, this extract seems to reduce the symptom severity and duration of symptoms.^13192,14345 More evidence is needed to confirm these findings before American ginseng can be recommended for this use.

Probiotics are gaining interest for reducing the risk of upper respiratory tract infections such as the common cold. Some research suggests that milk fortified with a specific strain of probiotic, Lactobacillus rhamnosus GG (Culturelle) seems to modestly reduce the incidence of respiratory infections in young children in day care.⁸⁵⁶⁵ Lactobacillus GG seems to stimulate some measures of immune function.^7756,7757 Some clinical research also shows that children attending day care who drink a milk product containing a specific combination of Lactobacillus acidophilus plus Bifidobacteria animalis (HOWARU Protect, Danisco) for 6 months have a 45% lower risk of developing flu-like symptoms compared to placebo. This is promising, but still preliminary.

Zinc inhibits rhinovirus replication in vitro, but there’s no evidence this happens in vivo. Some evidence suggests that zinc might also increase cell-mediated immune response in elderly people. But there’s also no reliable evidence that taking zinc supplements can help prevent a cold.^{10780,10783,10784} Zinc also does not seem to decrease the chance of getting the flu in vaccinated, institutionalized elderly patients.⁶⁵⁶³

Vitamin C has long been promoted for colds and flu and has generated lots of controversy over the years. Vitamin C might help immune function. It seems to increase T-lymphocyte activity, phagocyte function, leukocyte mobility, and possibly antibody and interferon production.^1963,1965 But most evidence suggests that even in doses up to 1 gram/day, vitamin C does NOT prevent colds.^{1966,1967,1968,1987,3042,6458,7101,9832} Likewise, increasing DIETARY vitamin C intake does not seem to affect the risk of getting a cold.¹⁰⁷⁸⁰

What Else Works?

The most common sense preventive measure by far is hand washing. This is a crucial, simple idea that really does cut down on passing along the infection via handshaking or touching. This has been proven for almost 200 years, ever since Dr Lister proved that hand washing with antiseptic dramatically cut down on surgical infections (be thankful you didn’t live back then!). Many studies since then have shown decreases in hospital acquired infections with simple hand washing. But people should not waste their money on the trendy anti-microbial soaps with triclosan and other ingredients as they don’t have much evidence of effectiveness, and they likely will lead to a worsening of the already serious worldwide problem of antibiotic resistance. Simple soap and water also does the trick — but I actually prefer the alcohol gels as they work quicker and wipe out a much larger percentage of viruses and bacteria than soap.

Another interesting idea is daily gargling, with simple salt water, during the entire winter season. In a 2005 published study in the American Journal of Preventive Medicine, people who gargled up to three times a day had a 40% decrease in respiratory illness and symptoms during the winter. Gargling also is a simple way to help improve sore throat pain and swelling, and it also loosens up mucus.

And of course, the basics

Don’t forget the obvious concept of a healthy immune system, via exercising, a good diet full of antioxidants, and not smoking!