A medical revolution is on the horizon … and it has nothing to do with drugs.
It's long been known that the human body plays host to many microbes, most of which are either harmless (commensal) or beneficial (symbiotic).
Compared with your own human cells, there are 10 times as many microbial cells in your body, encompassing some 10,000 different species.
This collection of ecosystems is collectively called the “microbiome”, which is estimated to constitute from seven ounces to three pounds of the average adult's body weight.
How your microbiome affects your health:
Video from NPR provides an animated overview
Not until the late 1990s did research begin to uncover the broad health effects and critical importance of the human microbiome.
In fact, its importance to health has led some doctors to propose dividing people into one of three major “enterotypes”, to enable more accurate and effective diagnoses and prescriptions, based on the composition of the gut microbiome.
The ever-growing list of conditions apparently promoted or affected by the human microbiome includes colds and respiratory infections, cardiovascular disease, obesity, allergies, asthma, depression, anxiety, autism, stress, female urogenital diseases, inflammation, sinusitis, and certain cancers.
Surprisingly, the microbiome plays a key role in the immune system, which may explain why certain microbiome blends can raise your risk for chronic inflammation or auto-immune diseases (e.g., rheumatoid arthritis, type I diabetes, Crohn's disease, multiple sclerosis, and fibromyalgia).
Our gut microbiome also affects how we metabolize carbohydrates and foods in general … stunning findings with major implications for vulnerability to obesity and type II diabetes.
For a friendly introduction to this topic, view an entertaining video from National Public Radio, called The Invisible Universe of The Human Microbiome.
Modern life is bad news for your microbiome … and a baby's
Living in modern industrialized societies seems to impair and imbalance the microbiome.
Unhealthy microbiomes – and vulnerability to allergies and diverse diseases – have been traced to the unprecedented sterility of our home and work environments … and to the rise in births by Cesarean section (Fujimura KE et al. 2013; Makino H et al. 2013).
Up until the mid-20th century, most children lived on farms or in messy, manure-strewn cities, and were exposed to a wide variety of microbes from birth.
And during vaginal births, babies' orifices become seeded with beneficial bacteria from their mothers' birth-canal microbiome.
These societal shifts have brought unintended consequences, in the form of rising rates of diseases now linked to inferior human microbiomes.
Probiotics: Bacterial promoters of microbiome health
Most Americans encounter this world through ads for “probiotic” yogurts … a term that refers to supplements or foods rich in beneficial bacterial cultures, including yogurt, kefir, raw-milk cheeses, and raw, cultured vegetables.
Slapping a “probiotic” label on a product implies that it will seed the gut with friendly microbes, which is generally true.
(The companion term “prebiotic” refers to indigestible starches that serve as the primary foods for friendly gut bacteria, and foster their growth. Some prebiotics, such as FOS and inulin, are sold as supplements.)
Makers of probiotic supplements typically claim that these capsules or liquids will deliver billions of beneficial lactobacilli to your gut, intact and alive.
But they rarely possess or offer any proof for this claim ... or for the unstated implication that their supplements will bring health benefits.
Despite that caveat, there's substantial evidence that probiotic foods and supplements can help improve certain aspects of health for certain people in certain circumstances.
And there's universal agreement that probiotics will not harm your health.
For more on this topic, see “Can probiotic foods and pills enhance overall health?”, below.
Probiotics as disease treatments and preventers
Attempts to manipulate the microbiome to prevent or treat various diseases have produced mixed results ... but some efforts have seen startling successes.
For example, fecal microbiota transplantation (FMT) is a proven (albeit icky) therapy for people who receive antibiotics and then suffer a stubborn infection by a very bad bug called Clostridium difficile.
Likewise, a few people with chronic sinus or ear infections have been helped by receiving nasal mucous or ear wax transplants from a healthy donor, while mice with sinus infections have been cured by insertion of a particular type of Lactobacillus bacteria (Abreu NA et al. 2012).
Which is better ...
... foods or pills?
The answer to this question remains unclear, in part because it depends on the probiotic used and the genome and health of the person consuming them.
However, it seems likely that for overall health enhancement (versus specific therapeutic needs), foods offer an edge.
No doubt, this general presumption – prompted by what's known about the health effects of whole foods versus supplements (see “Whole Foods Seen Superior to Supplements”) – will prove to have many exceptions.
For now, as the authors of a recent evidence review wrote, “… [probiotic] foods and supplements have been able to confer the health benefits claimed for them.”
“However, it is not known which one can be clinically more efficient, and … no research has been conducted to investigate this issue.” (Rad AH et al. 2014)
Their conclusion fits with most evidence concerning the superior benefits of whole foods:
“Although both foods and supplements seem to have been efficient carriers for the beneficial bacteria, to generally promote public health in communities, probiotic foods appear to be preferred to probiotic supplements.” (Rad AH et al. 2014)
And substantial evidence suggests that yogurt or supplements rich in Lactobacilli can help prevent or treat vaginal yeast and bacteria infections (Van Kessel K et al. 2003).
Some studies also suggest that when expectant mothers take probiotic supplements, their children are less likely to develop allergies or asthma (Azad MB et al. 2013).
Can probiotic foods and pills enhance overall health?
It's become hard to escape TV ads that make claims for the benefits of the proprietary blend of probiotic bacteria in a particular brand of yogurt.
In addition, it appears that the polyphenol-type antioxidants in tea, cocoa, and many herbs, spices, and plant foods may improve the microbiome … see “Cocoa and Dark Chocolate May Aid Gut Health” and “Tea May Enhance Intestinal Health and Immunity”.
Ample research suggests that the lactobacillus-type bacteria in yogurt and other traditional, fermented foods can benefit human health … to slight, modest, or dramatic degrees (El-Abbadi NH et al. 2014; Lin CS et al. 2014; DuPont AW, DuPont HL 2011).
But because probiotic research is its infancy, it can be hard to tell reality from hype.
Scientists still can't say whether a given fermented food or probiotic supplement will improve a particular aspect of a given person's health.
Recent research from Canada's Laval University found that while probiotic yogurt increased the numbers of beneficial lactobacilli-type bacteria in consumers' guts, it did not change the overall makeup of their microbiomes (Filteau M et al. 2013).
However, as co-author Denis Roy said, “If the overall microbiota makeup is unchanged, it does not mean that probiotic yogurt is ineffective, since it could have [beneficial] metabolic effects. More studies are needed.”
And, as Dr. Roy noted, it can't hurt to eat probiotic supplements or fermented foods: “Probiotics have no adverse effects, [such] as reducing bacteria diversity of the intestinal microbiota.”
In other words, it seems very smart to fill your meals with plain, unsweetened yogurt or kefir, fermented/cultured vegetables … and all kinds of flavorful, “living” foods.
  • Abreu NA, Nagalingam NA, Song Y, Roediger FC, Pletcher SD, Goldberg AN, Lynch SV. Sinus microbiome diversity depletion and Corynebacterium tuberculostearicum enrichment mediates rhinosinusitis. Sci Transl Med. 2012 Sep 12;4(151):151ra124. doi: 10.1126/scitranslmed.3003783.
  • Azad MB, Coneys JG, Kozyrskyj AL, Field CJ, Ramsey CD, Becker AB, Friesen C, Abou-Setta AM, Zarychanski R. Probiotic supplementation during pregnancy or infancy for the prevention of asthma and wheeze: systematic review and meta-analysis. BMJ. 2013 Dec 4;347:f6471. doi: 10.1136/bmj.f6471. Review.
  • da Silva ST, dos Santos CA, Bressan J. Intestinal microbiota; relevance to obesity and modulation by prebiotics and probiotics. Nutr Hosp. 2013 Jul-Aug;28(4):1039-48. doi: 10.3305/nh.2013.28.4.6525. Review
  • Delia A, Morgante G, Rago G, Musacchio MC, Petraglia F, De Leo V. [Effectiveness of oral administration of Lactobacillus paracasei subsp. paracasei F19 in association with vaginal suppositories of Lactobacillus acidofilus in the treatment of vaginosis and in the prevention of recurrent vaginitis]. Minerva Ginecol. 2006 Jun;58(3):227-31. Italian.
  • El-Abbadi NH, Dao MC, Meydani SN. Yogurt: role in healthy and active aging. Am J Clin Nutr. 2014 May;99(5 Suppl):1263S-70S. doi: 10.3945/ajcn.113.073957. Epub 2014 Apr 2. Review.
  • DuPont AW, DuPont HL. The intestinal microbiota and chronic disorders of the gut. Nat Rev Gastroenterol Hepatol. 2011 Aug 16;8(9):523-31. doi: 10.1038/nrgastro.2011.133. Review.
  • Filteau M, Matamoros S, Savard P, Roy D. Molecular monitoring of fecal microbiota in healthy adults following probiotic yogurt intake. PharmaNutrition (Article in Press). http://dx.doi.org/10.1016/j.phanu.2013.05.002
  • Fujimura KE, Demoor T, Rauch M, Faruqi AA, Jang S, Johnson CC, Boushey HA, Zoratti E, Ownby D, Lukacs NW, Lynch SV. House dust exposure mediates gut microbiome Lactobacillus enrichment and airway immune defense against allergens and virus infection. Proc Natl Acad Sci U S A. 2014 Jan 14;111(2):805-10. doi: 10.1073/pnas.1310750111. Epub 2013 Dec 16.
  • Ianiro G, Bibbò S, Gasbarrini A, Cammarota G. Therapeutic modulation of gut microbiota: current clinical applications and future perspectives. Curr Drug Targets. 2014;15(8):762-70.
  • Khan MS, Bawany FI, Khan A. Intestinal microbiota produced trimethylamine-N-oxide can increase the risk of cardiovascular disease. J Pak Med Assoc. 2014 Apr;64(4):488.
  • Khoruts A, Weingarden AR. Emergence of fecal microbiota transplantation as an approach to repair disrupted microbial gut ecology. Immunol Lett. 2014 Aug 10. pii: S0165-2478(14)00156-4. doi: 10.1016/j.imlet.2014.07.016. [Epub ahead of print] Review.
  • Kurita-Ochiai T, Yamamoto M. Periodontal pathogens and atherosclerosis: implications of inflammation and oxidative modification of LDL. Biomed Res Int. 2014;2014:595981. doi: 10.1155/2014/595981. Epub 2014 May 18
  • Lin CS, Chang CJ, Lu CC, Martel J, Ojcius DM, Ko YF, Young JD, Lai HC. Impact of the gut microbiota, prebiotics, and probiotics on human health and disease. Biomed J. 2014 Sep 2. doi: 10.4103/2319-4170.138314. [Epub ahead of print]
  • Makino H, Kushiro A, Ishikawa E, Kubota H, Gawad A, Sakai T, Oishi K, Martin R, Ben-Amor K, Knol J, Tanaka R. Mother-to-infant transmission of intestinal bifidobacterial strains has an impact on the early development of vaginally delivered infant's microbiota. PLoS One. 2013 Nov 14;8(11):e78331. doi: 10.1371/journal.pone.0078331. eCollection 2013.
  • Maukonen J, Saarela M. Human gut microbiota: does diet matter? Proc Nutr Soc. 2014 Aug 26:1-14. [Epub ahead of print]
  • McNulty NP, Yatsunenko T, Hsiao A, Faith JJ, Muegge BD, Goodman AL, Henrissat B, Oozeer R, Cools-Portier S, Gobert G, Chervaux C, Knights D, Lozupone CA, Knight R, Duncan AE, Bain JR, Muehlbauer MJ, Newgard CB, Heath AC, Gordon JI. The impact of a consortium of fermented milk strains on the gut microbiome of gnotobiotic mice and monozygotic twins. Sci Transl Med. 2011 Oct 26;3(106):106ra106. doi: 10.1126/scitranslmed.3002701.
  • Rad AH, Mehrabany EV, Alipoor B, Mehrabany LV. The comparison of food and supplement as probiotic delivery vehicles. Crit Rev Food Sci Nutr. 2014 Aug 13. [Epub ahead of print]
  • Van Kessel K, Assefi N, Marrazzo J, Eckert L. Common complementary and alternative therapies for yeast vaginitis and bacterial vaginosis: a systematic review. Obstet Gynecol Surv. 2003 May;58(5):351-8. Review.