EAT A PEACH | Beneficial Bacteria

By ELLA NONNI

In the past decade, bacteria have gone from infectious pests to digestion aiding assets. It is common knowledge that yogurt is good for an upset stomach, or that you should eat yogurt while taking antibiotics, but now probiotic supplements have an entire section in every drugstore, and innovative, probiotic-rich foods like kombucha and kefir are increasing in popularity. Bacteria were first discovered as the culprits of disease, and since then, we have spent the majority of our scientific history studying the pathogens. Only recently have we begun to uncover the major role beneficial bacteria play in our body systems, and it turns out their significance is unparalleled.

A Complex Ecosystem

We used to think that the body itself was capable of carrying out all its functions as an independent organism. Now were discovering that is a far cry from reality. Science writer Jennifer Ackerman explains, [The body] is more like a complex ecosystem a social network containing trillions of bacteria and other microorganisms that inhabit our skin, genital areas, mouth and especially intestines. Most cells in the human body are not human cells at all; in any given individual, bacterial cells outnumber human cells 10 to one. Latest research suggests that in the human digestive system alone there are over 1,000 bacterial species, comprising over 3.3 million genes 150 times the total number of genes in the human body. The Human Genome Project revealed that all humans share 99.9% of their DNA, giving us little basis to explain why individuals and populations appear to vary so greatly. One explanation may be the variations in our microbial makeup, which influence our digestion, immunity, reproduction and behavior.

We spent hundreds of thousands of years evolving as humans, but we were not only adjusting to our environments we were adjusting in order to live in harmony with the microorganisms in them. We are at the point where our bodies could not carry out functions necessary for survival without the aid of these symbionts. With the advent and rapid rise in antibiotic use, we have inadvertently disrupted our microbial communities, and therefore our entire bodys homeostasis. We are just beginning to understand how current health crises, such as obesity and autoimmune disorders, may be influenced by this disruption.

Obesity

Probiotic bacteria do more than just synthesize vitamins and break down indigestible foods they also play a major role in the regulation of appetite. The bacterium Helicobactor pylori, for example, is a commensal that was previously demonized as a pathogen for its role in the development peptic ulcers in susceptible individuals. Not only does H. pylori actually regulate stomach acid levels, but it is involved in regulating ghrelin, the hormone responsible for hunger. Researchers are still not sure how it does this, but in persons with no H. pylori, ghrelin levels do not decrease after eating like they are supposed to. Consequently, these individuals experience prolonged hunger, and in studies, gained significantly more weight than those who had the bacterium in their gastric flora. A few generations ago (before the advent of antibiotics), more than 80% of Americans were hosts to H. pylori. Now less than 6% of American children test positive. Most children in the U.S. have been on antibiotics multiple times by the age of 15 for various common illnesses like ear infections and strep. Some researchers theorize that widespread use of antibiotics in children (and thus the elimination of bacteria like H. pylori) helps to explain the rising rates of childhood obesity. Microorganisms also assist in the transformation of stem cells into fat, muscle or bone cells during child development. Interrupting the bacteria that aid this process may be causing the overproduction of fat cells (and underproduction of bone and muscle).

Finally, antibiotics themselves, as livestock farmers know, accelerate weight gain. In her New York Times article, Pagan Kennedy claims that decades of agricultural research have shown that antibiotics seem to flip a switch in young animals bodies, helping them pack on pounds. In the 1950s, scientists fed antibiotics to schoolchildren in Guatemala for over a year. The group supplemented with antibiotics gained an average of 6.5 lbs per year while the control group averaged 1.9 lbs. This antibiotic effect is especially potent when the drugs are combined with calorie-dense foods, which are more available than ever before in the United States.

Autoimmune disorders

Even our immune systems require the assistance of commensal bacteria in order to function properly. Its rather ironic the immune system, whose goal is to detect and eliminate harmful bacteria, can only function with the help of other non-harmful bacteria. The bacterium Bacteroides fragilis, for instance, regulates the balance between pro-inflammatory and anti-inflammatory T cells. The immune systems of mice withoutB. fragilis were defective, and their regulatory T cells underperformed. When B. fragilis was reintroduced, immune function was restored.

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EAT A PEACH | Beneficial Bacteria