American Society For Nutrition

Can probiotics affect novel H1N1 influenza?

Can probiotics affect novel H1N1 influenza?

Excellence in Nutrition Research and Practice
Posted on 08/03/2009 at 10:54:55 PM by Student Blogger

By: Erik K.

Since its appearance early this year, the novel H1N1 strain of influenza has garnered a large amount of attention from both research scientists and the general media. Recently, the Centers for Disease Control released a projection that, in a worst-case scenario, the virus could affect up to 40% of the US workforce (including those who contract the virus and those staying home to care for the ill). The CDC also predicts that, in this situation, anywhere between 90,000 and "several hundred thousand" Americans could die of novel H1N1 influenza infection or flu-related illnesses (1) Of course, I am assuming that “worst-case scenario” means catastrophic vaccine failure or a major mutation in the virus. Recently, I have run across a number of internet rumors that a homeopathic solution to reduce the severity of the H1N1 pandemic may be the use of probiotics. Being the ever doubtful nutritional immunology researcher, I decided to delve into this rumor to see if there was any truth to the matter.

First of all, I think that I need to define the terms probiotic and probiotic food. In this case, I'll be using a broad definition proposed by the FAO/WHO in 2001 stating that probiotics are “live microorganisms which, when administered in adequate amounts, confer a health benefit to the host” (2). Taking this definition for probiotic, then a probiotic food could be defined as those foods which contain adequate amounts of living, probiotic microorganisms in an adequate environment to confer a health benefit following consumption. There are a large number of “probiotic” foods on the market with a majority of the probiotic microorganisms belonging to the genera Lactobacillus and Bifidobacterium, which are gram-positive lactic acid-producing bacteria that constitute a major part of the normal human intestinal flora (3).

Now, you are probably asking yourself, can eating microorganisms (ie: bacteria) boost my immune system? Indeed, it seems that probiotic microorganisms and their components have been shown to have some immunomodulatory effects. Probiotics have been shown to stimulate T cell proliferation as well as stimulate natural killer cells and macrophages, increase antiviral cytokine release and shift the immune balance towards a Th1 response in in vitro and in animal models; however, this may only be indications to their beneficial effects.  These results have been replicated, at least, in part, in human trials (Reviewed in 4-7).

So, hypothetically, probiotics may be able to boost the immune system to help fight off a viral infection.  However, here is where we run into a major problem. Stimulation of the immune system itself does NOT imply a positive health benefit for a specific virus. To be able to say that requires clearly defined, controlled clinical trials showing therapeutic effects of probiotics against a specific infection. The few studies I found looking at viral respiratory tract infections (eg: common cold, influenza) did show some promising reduction in the severity and duration of illness and even promoting vaccine response; however, to date these have been smaller trails in select populations using particular strains of probiotics (8-10). What we have to remember is that judging the effect of a probiotic food is extremely difficult. The proof that a probiotic component of a food is beneficial is only valid for the strain with which the study has been performed. Indeed, the benefit may only be considered beneficial for that specific strain, at those specific absolute numbers, in that specific composition and physical state in that specific target group (3).

Don't get me wrong. I think we can all agree that a dietary supplement which could help reduce the severity of novel H1N1 infection would be greatly beneficial to society.  I do think that probiotic supplements can eventually be used for immunomodulatory effects. In fact, some probiotics may be perfect candidates for prevention and/or treatment of common respiratory tract infections in certain populations. I'm just skeptical that these results are generalizable to the world population. Even more worrisome is the lack of data on overdosage or long-term consequences of ingesting these microorganisms. Further studies need to be conducted to determine specific groups where these supplements are beneficial. Until then, keep living a healthy lifestyle, eat a balanced diet and get vaccinated.

2. FAO.WHO Health and Nutritional Properties of Probiotics in Food including Powder Milk with Live Lactic Acid Bacteria. Report of a joint FAO/WHO Exert Consultation 2001. Cordoba, Argentinia, 2001, 19-20.
3. de Vrese M, J Schrezenmeir. Probiotics, Prebiotics and Synbiotics. Adv Biochem Engin/Biotechnol. 2008; 111: 1-66
4. Lomax AR, Calder PC. Probiotics, immune function, infection and inflammation: a review of the evidence from studies conducted in humans. Curr Pharm Des. 2009;15(13):1428-518
5. Yoo J, Tcheurekdjian H, Lynch SV, Cabana M, Boushey HA. Microbial manipulation of immune function for asthma prevention: inferences from clinical trials. Proc Am Thorac Soc. 2007;4(3):277-82
6. Calder PC, Kew S.The immune system: a target for functional foods?Br J Nutr. 2002; 88(Suppl 2):S165-77
7. de Vrese M, Schrezenmeir J. Probiotics and non-intestinal infectious conditions. Br J Nutr. 2002;88(Suppl 1):S59-66
8. Baron M. A patented strain of Bacillus coagulans increased immune response to viral challenge. Postgrad Med. 2009;121(2):114-8.
9. Boge T, RÉmigy M, Vaudaine S, Tanguy J, Bourdet-Sicard R, van der Werf S.A probiotic fermented dairy drink improves antibody response to influenza vaccination in the elderly in two randomised controlled trials.Vaccine. 2009. [Epub ahead of print]
10. Winkler P, de Vrese M, Laue Ch, Schrezenmeir J. Effect of a dietary supplement containing probiotic bacteria plus vitamins and minerals on common cold infections and cellular immune parameters. Int J Clin Pharmacol Ther. 2005 Jul;43(7):318-26
Before agreeing that dietry suppliments could help reduce the sevierity of H1N1, would like to find out more, but this is a well explained post.

You've hit the nail on the head! Although certain probiotics have shown promising results, to prove conclusively that they either reduced the severity or duration of an illness is difficult.

However, I do not believe there should be any concern about their long term use. We, the human species, have been ingesting these beneficial lactic acid bacteria throughout our evolution. Our gastrointestinal tract - and probably our immune system - has evolved to work in harmony with them.

Studies have shown that the lactic acid bacteria that appear in many fermented dishes vary in different parts of the world. The ones that multiply are the ones best suited to fight the pathogens in that area.

So a dish of fermented grain in one African village may have differing beneficial bacteria in it to a similar dish in another part of Africa. Each particularly adept at fighting, or more likely, simply out-competing the pathogens likely to appear in that dish in that village.

Sometimes I think that "Mother Nature" is a great deal more clever than we appreciate.