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Preventing the Common Cold with Probiotics?

Though prebiotics may be preferable, probiotics may reduce the risk of upper respiratory tract infections.

May 27, 2013 |
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Supplementary Info

Sources Cited

P. Bager, J. Wohlfahrt, T. Westergaard. Caesarean delivery and risk of atopy and allergic disease: Meta-analyses. Clin. Exp. Allergy 2008 38(4):634 - 642

A. Berggren, I. L. Ahrén, N. Larsson, G. Önning. Randomised, double-blind and placebo-controlled study using new probiotic lactobacilli for strengthening the body immune defence against viral infections. Eur J Nutr 2011 50(3):203 - 210

A. H. Rad, F. Akbarzadeh, E. V. Mehrabany. Which are more important: Prebiotics or probiotics? Nutrition 2012 28(11 - 12):1196 - 1197

B. Vitali, G. Minervini, C. G. Rizzello, E. Spisni, S. Maccaferri, P. Brigidi, M. Gobbetti, R. Di Cagno. Novel probiotic candidates for humans isolated from raw fruits and vegetables. Food Microbiol. 2012 31(1):116 - 125

C. S. Benn, P. Thorsen, J. S. Jensen, B. B. Kjaer, H. Bisgaard, M. Andersen, K. Rostgaard, B. Björkstén, M. Melbye. Maternal vaginal microflora during pregnancy and the risk of asthma hospitalization and use of antiasthma medication in early childhood. J. Allergy Clin. Immunol. 2002 110(1):72 - 77

H. S. Gill, K. J. Rutherfurd, M. L. Cross, P. K. Gopal. Enhancement of immunity in the elderly by dietary supplementation with the probiotic Bifidobacterium lactis HN019. Am. J. Clin. Nutr. 2001 74(6):833 - 839

Y. H. Sheih, B. L. Chiang, L. H. Wang, C. K. Liao, H. S. Gill. Systemic immunity-enhancing effects in healthy subjects following dietary consumption of the lactic acid bacterium Lactobacillus rhamnosus HN001. J Am Coll Nutr 2001 20(Suppl 2):149 - 156

Q. Hao, Z. Lu, B.R. Dong, C.Q. Huang, T. Wu. Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev. 2011 9:1-42

L. Drago, V. Rodighiero, T. Celeste, L. Rovetto, E. De Vecchi. Microbiological evaluation of commercial probiotic products available in the USA in 2009. J Chemother 2010 22(6):373 - 377


Images thanks to Sofa-King and William Brawley via Flickr.


Babies delivered via caesarean section "appear to be at increased increase for various allergic diseases.” The thought is that vaginal delivery leads to the first colonization of the gut with maternal vaginal bacteria, while c-section babies are deprived of this natural exposure, and exhibit a different gut flora. This is supported by research noting that a disturbance in maternal vaginal flora during pregnancy may be associated with early asthma in their children. This all suggests our natural gut flora can affect the development of our immune system for better or for worse.

In adulthood, two studies published back in 2001 suggested that probiotics could have systemic immunity enhancing effects. Subjects were given a probiotic regimen between weeks three to six and saw a significant boost in the ability of their white blood cells to chomp down on potential invaders. And what's interesting is that even after the probiotics were stopped there was still enhanced immune function a few weeks later compared to baseline. The same boost was found in the ability of their natural killer cells to kill cancer cells.  Similar results were also found using a different probiotic strain.

Improving immune cell function in a petri dish is nice, but does this actually translate into people having fewer infections? For that, we had to wait another 10 years, but now we have randomized double-blind placebo controlled studies showing that those taking probiotics may have significantly fewer colds, fewer sick days, and fewer symptoms. 

The latest review of the best studies to date found that probiotics, such as those in yogurt, soy yogurt, or supplements, may indeed reduce one's risk of upper respiratory tract infection, but the totality of evidence is still considered weak, so it's probably too early to make a blanket recommendation.

Unless one has suffered a major disruption of gut flora by antibiotics, or an intestinal infection—unless one is symptomatic—with like diarrhea or bloating, I would suggest focusing on feeding the good bacteria we already have, by eating so-called prebiotics, such as fiber. After all, as we saw before, who knows what you're getting when you buy probiotics, they may not even even be alive by the time you buy them. They have to survive the journey down to the large intestine. Altogether, these points suggest that the advantages of prebiotics—found in plant foods--outweigh those of probiotics. And by eating raw fruits and vegetables we may be getting both. Fruits and vegetables are covered with millions of lactic acid bacteria, some of which are the same type used as probiotics. So when studies show eating more fruits and vegetables boosts immunity, prebiotics and probiotics may be playing a role.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.

To help out on the site please email

Dr. Michael Greger

Doctor's Note

Probiotics do play an established role in helping to prevent antibiotic-associated diarrhea and may speed recovery from acute gastroenteritis. See my last video, Preventing and Treating Diarrhea with Probiotics. When should they be taken? That's the subject of my next video, Should Probiotics Be Taken Before, During, or After Meals?

How else might we reduce our risk of getting an upper respiratory infection? See:

You can watch a video of white blood cells actually chomping down on foreign invaders in my video Clinical Studies on Acai Berries. A must-see for biology geeks!

The immune boosting fruit and vegetable video I reference is Boosting Immunity Through Diet. See also Kale and the Immune System and last week's video Boosting Immunity While Reducing Inflammation.

For more context, check out my associated blog posts:  Probiotics and DiarrheaProbiotics During Cold Season?Probiotics During Cold Season?How Should I Take Probiotics?How Probiotics Affect Mental Health, and Top 10 Most Popular Videos from 2013

If you haven't yet, you can subscribe to my videos for free by clicking here.

  • HemoDynamic, M.D.

    Nice presentation of pre and probiotics!

    3-4 trillion cells and 30-40 trillions of bacteria living in dynamic equilibrium–that’s the amazing human body!

    Kinda weird to think I am just a large bag of bacteria using my flagella (arms and legs) to make my way through life.

    • Plantstrongdoc

      Once in a while you probably also use your brain – sure sounds like that! :-)

      • HemoDynamic, M.D.

        Sometimes, but sometimes it’s just fun to walk around waving my arms and legs wildly.

        “Warning!! Danger, Will Robinson!”


  • Veganrunner

    You have done it again. You start a series and I end up with more questions. Then by the end you have answered them all! I will keep eating my fruits and vegetables and feed my friendly gut friends.

    • Plantstrongdoc

      Dr G is also master of suspense….

  • Wegan

    Wait a minute. Don’t we wash and cook the veggies to get rid of the bad bacteria?

    • Wegan

      Also, what about kimchee and cancer? The more I learn the more confused I am.

  • mcooks

    I live in South America and have to soak my fruits and veggies in water with grapefruit seed extract to clean them. Does this kill the beneficial bacteria, like probiotics, also? Is there a better way to clean my veggies (remember that even the water here isn’t safe to drink) that would maintain the beneficial bacteria? Thank you for the great information.

    • Coacervate

      I live west of you on an island where we collect roof water into cisterns and use that for everything. And we have high rates of asthma and water-borne disease. Two things I would suggest is use aeration in the water. I’m told it reduces the anaerobes (bad bugs are often that type). Second, pathogens are often gram-negatives (in this case gram refers to a type of dye). I’m no microbiologist but my reading indicates that gram negatives die when dried out. The good bugs are gram positive and can withstand a good drying. I’m sure others here will know how true or effective this is likely to be.

      We keep a supply of boiled drinking water at all times. Say, what does grapefruit seed extract do ? disinfect?

  • whole plant eater

    Having a breakfast smoothie of fruit, vegetables, bran and fresh kefir that I make has relieved me of all irritable bowel symptoms I had for the past 10 years. though, I can still get a upper respiratory tract infection, it seems less frequent.

  • Coacervate

    I was so freaked out by the veg-borne E. coli infections , for a while I washed all the raw stuff obsessively. Even using dilute bleach to disinfect… AND yet I was so sick with IBS type syptoms for years. Finally I started growing most of what we eat. Now everything gets a quick rinse, then onto the plate. Not unusual to pick off a green cabbage patch caterpillar hanging onto some kale, they don’t seem to mind. Guess what, almost all my colon problems are history. Over the past 2 years things continuously improved. I’m told I can be heard singing Rocky (“gonna fly now…”) almost exactly the same time every morning.

    I make my own compost using our own stuff on our little 5 acre plot. Pet chickens, a 3 year old heifer, a way too fat ewe and goat, greens and browns… all contribute to our garden soil. So we can imagine the variety of bugs we eat and where they’ve been! But by the end of the composting process the whole ecosystem has speed-volved into real soil for real plants. Contrast with Industrial food growers who shortcut the process and expose your lovely veg to toxic poopie before its been worked over by the natural succession of microflora during proper composting.

    My point being, I’m sure this vid is spot on partly because the science supports it but also my personal experience has been so positive. I understand the path to the real dirt on farming. I can feel it in my bowels. I just want to go the distance!

    Thanks once again Dr. G!

    • Veganrunner

      Absolutely wonderful life!

  • Brian Humphrey

    Thank you once again Dr. Greger! You keep giving me reasons to continue eating a plant-centered diet! I also feel great too!

  • Green Zizzle

    Does this work because my colds are soo bad.

    London garage rentals

  • liowik

    Dr. Gregor, have you determined from the studies which was the most accurate brand of probiotics to take? What’s your recommendation?

  • Wendy

    In the store there are probiotics that are in bottles on the shelf or there are one that are in the refrigerator. Are there refrigerated ones better? They certainly are more expensive but if they are better for us then they are worth the price.

  • believeinbee

    I do have one question, I noticed you don’t have any info on kefir or did I just fail to notice it. Just curious what your opinion on kefir is, is it as healthy as we make it out to be?

    Thank you

    • Thea

      believeinbee: I am aware of two types of kefir – one that is grown in a water base and one that is grown in a dairy/milk base. And Dr. Greger has much to say about the problems with dairy!:

      I think that people tout kefir as being healthy because it has probiotics in it. Dr. Greger also has a lot to say about probiotics. You can get what you need, especially with pre-biotics without resorting to dairy. So, while I don’t speak for Dr. Greger, I think the bottom line is that Dr. Greger would not recommend dairy kefir, because food is a package deal and the benefits do not outweight the harms.

      Hope that helps.

  • Nyx

    In the Journal of Chemotherapy artice: Microboilogical Evaluation of Commercial Probiotic Products Available in the USA in 2009 I was wondering what are the names of the probiotic products that actually contained what was put on their labels?