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These consequences not only affect our individual health, but may even be causing permanent changes to the microflora of all people from generation to generation.
Martin Blaser's recent (2011) article published in Nature highlights the potentially dangerous long-term consequences that arise from the rampant overuse of antibiotics. (1) He argues that changes in our microbiota may even be promoting the transmission of deadly organisms, as one of the important roles of an intact microflora is to resist colonization by pathogenic organisms.
Blaser also points out that not only does the individual use of antibiotics cause permanent changes in the gut flora, but that infants born to women given antibiotics during pregnancy, or the 30% of children delivered via cesarean section, may be starting life with a significantly altered and insufficient level of friendly gut flora. (2) This is a serious concern because lack of diversity in friendly gut bacteria has been shown to contribute to a large number of diseases and complications.
Unfortunately, even a single course of antibiotics can permanently alter the gut flora.
One study found that after a single treatment of intravenous antibiotics, fecal bacteria tests demonstrated a significant change in the variety of bacterial strains, and the development of the pathogen Clostridium difficile. (3) C. difficile colonization in the gut can lead to serious complications such as severe diarrhea and colitis. (4)
Another study demonstrated that a short course of the antibiotic ciprofloxacin reduced the diversity of the intestinal microbiota, with significant effects on roughly one-third of the bacterial species. (5) This study also found that while much of the diversity eventually recovered, there were still several species that failed to recover after six months, suggesting that even a short course of antibiotics may cause permanent changes to the community of friendly flora in the gut.
Antibiotics are known to cause diarrhea, which may be due to infection by antibiotic resistant pathogens such as salmonella, C. perfringens type A, Staphylococcus aureus, and possibly Candida albicans, as well the various metabolic consequences of reduced concentrations of fecal flora. (6) These results suggests that disturbance of the normal intestinal flora following antibiotic use may be responsible for the overgrowth of dangerous pathogens.
Research also indicates that infants' gut flora is significantly affected by cesarean delivery, which requires the administration of antibiotics to the mother. One study demonstrated significant changes in the primary intestinal flora of infants born through cesarean delivery, lasting at least six months. (7) Primary colonization of the newborn's sterile intestinal tract normally happens during vaginal birth, and it is unknown whether an infant born with inadequate or unbalanced colonization will ever develop normal intestinal flora without intervention.
While breastfeeding can help restore some of the natural balance to the microflora, only about 44.3% of American women breastfeed (with only 14.8% breastfeeding exclusively) for the full six months that is recommended. (8, 9) Furthermore, breastfeeding alone may not compensate for the changes in flora associated with cesarean sections, suggesting that many infants may be at an even greater disadvantage when it comes to the proper development of a healthy, functional digestive tract. (10)
Research from diverse fields demonstrates the negative effects of gut dysbiosis and inadequate friendly flora on a variety of health outcomes.
For example, resident bacteria of the normal flora are involved in intestinal mucosal inflammation and patients with inflammatory bowel disease (IBD) have higher amounts of bacteria attached to their intestinal mucosa than do healthy people. (11) Patients with Crohn's disease and ulcerative colitis are found to have reduced concentrations of fecal Lactobacillus and Bifdobacteria, which protect against pathogenic bacteria, increase mineral absorption and induce the production of growth factor in the gut. (12)
An unbalanced microbiota in the gut is also a contributing factor in autoimmunity. (13) Infection with certain microbial pathogens can trigger autoimmune reactions in joints and other organs. (14) The destruction of healthy gut flora can make the mucosal lining more susceptible to leakage, which some researchers believe is a precondition for developing autoimmunity. (15, 16) It is well-established that the balance of gut bacteria plays a key role in the formation of a proper immune response. (17, 18) A lack of healthy gut bacteria is associated with allergies, IBD, and general autoimmune reactions when this immune modulation goes awry.
New research has linked changes in gut bacteria with obesity. One study found that the gut bacteria of obese subjects different significantly in species type than lean subjects, and that low calorie diets, restricting either fat or carbohydrates, changed the gut flora and increased the abundance of the bacterial strains found more predominantly in the lean subjects. (19) Another study found that transplanting fecal bacteria from lean or obese mice into mice with sterile guts could affect whether these mice gained body fat, even when food intake was controlled. (20) Those mice implanted with fecal bacteria from obese mice gained a significantly larger percentage of body fat than those transplanted with bacteria from lean mice. The authors hypothesized that certain types of gut flora are associated with obesity due to the increased extraction of energy from the diet. I've written about this in more detail here.
These studies demonstrate the wide range of potential consequences caused by the improper development or destruction of the intestinal flora.
Though antibiotics may be necessary in certain situations, it's important to weigh the benefits of using them with the potential risks that may come from the permanent alteration of the gut flora. If antibiotics must be used (and there are certainly situations where this is the case), special care should be taken to not only restore their gut flora using probiotic foods and supplements, but to eat a diet that supports healthy gut microbiota with plenty of fermentable fibers from starch and the removal of food toxins.
To protect infants' gut health, especially those infants born through cesarean section, it is crucial to exclusively breastfeed for at least six months, with breastfeeding continuing on-demand throughout the complementary feeding period (up to 2 years of age). I also recommend using a high-quality infant probiotic to help populate your baby's gut with beneficial flora, as I explain in this article from my natural childbirth series.
Infancy is a critical time where the development of a healthy gut microbiota is essential for the long term health of your child. You can read more about protecting the gut health of your child in The Healthy Baby Code.
In medicine and health, as in all other areas of life, each choice we make comes with consequences. The purpose of this post is not to suggest that antibiotics are "bad" and we should never take them. As I said in the beginning of the article, antibiotics save lives and have significantly lengthened our lifespans. But that benefit has come with a price, and it's one that we're only just beginning to understand the full implications of. My goal here is simply to raise awareness of this price - the harmful and potentially lasting effects of antibiotics - so that you can make a more informed choice.
What are some alternatives to antibiotics?
Mark Sisson wrote a good post listing some alternatives to antibiotics a few months back. In my practice I use a combination of botanical anti-microbials, biofilm distruptors (bacteria often live in extracellular matrices called biofilm, which protect them from our innate immune defenses and any external anti-microbials we might take), and probiotics - as well as micronutrients to support immune function, like vitamin C, iodine and selenium.
While these botanicals do have an impact on the gut flora, it is less pronounced than the effect of broad-spectrum antibiotics. Still, I recommend taking any strong anti-microbials under the supervision of a qualified health care provider.
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