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Are You Ruled by the Bacteria in Your Gut?


Image credit: Brynn. You don’t REALLY want this, it’s your internal bacteria that want it.

Imagine when you are on a diet, if you reach for the tasty piece of chocolate, are you doing it out of your own mind, or are you actually manipulated by the bacteria in your gut?

This is the question raised by Dr. Carlo Maley from the University of California San Francisco in BioEssay. “Bacteria within the gut are manipulative,” Marley said. “The bacteria are diversified in different interests, and some of them are aligned with our own dietary goals while others are not.”

It might sound ridiculous to believe that our behavior is controlled by life forms that are so small, but please remember that the bacteria within our body outnumber our own cells at least 10 to 1 (some estimates say 100 to 1).

bacteria control behavior

UC San Francisco. Proposed mechanism by which gut bacteria control our behavior.

Our guts are filled with different bacteria species and they preferred various foods. According to co-author of the study, Dr. Athena Aktipis, from Arizona State University, although we benefit from bacteria’s ability to break down nutrients we cannot, such symbiotic relationship has its tensions. The healthiest diet for certain species of bacteria might not always benefit us, or those in our internal ecosystem.

The question here is whether these bacteria could affect what we eat to their benefit. Maley and Aktipis believe that they can by releasing molecules into our digestive system that are transmitted through the nervous, immune, and endocrine systems and signal to the brain what to put into our mouths. You can think of this as the bacteria’s way to order fast foods.

The authors recommend a test of their theory the bacteria are running the show. Seaweed is a common food in Japan and an important part of the local diet, and under this circumstance, bacteria that specialize in digesting seaweed are common to exist. If seaweed-specialized bacteria are transferred to the gut of someone on a western diet, will they begin to get cravings? Of course, it can easily be the other way around – seaweed-specialized bacteria become common in areas where it is a common dish.

Fortunately however, we are not simply at the will of the tiny yet numerous rulers, and we can stage a revolt. “Our diets have great influence on microbial populations in the gut. It’s a whole ecosystem, and it is evolving on the time scale of minutes,” says Maley. If you switch to a new diet, the change in species distribution of bacteria inside us will be measurable within 24 hours, as those that benefit from the new diet multiply.

This explains why probiotics can enhance not only our health but our mood. The authors note: “Because microbiota are manipulatable easily by probiotics, prebiotics, antibiotics, fecal transplants, and dietary changes, and altering our microbiota provides a tractable means to otherwise intractable problems of unhealthy eating and obesity.”