Is your Stomach… Controlling your Mind?

Close the blinds, lock the doors, and find a safe place to hide. Are you alone? No, no you aren’t and you may not even be in control of your own actions. Shhh, take a deep breath. I don’t want to alarm you, but you are being controlled. No, I’m not being paranoid and while it may sound like science fiction it looks like that bacteria within us — which for the record outnumber our own cells about 100-fold — may very well be affecting both our cravings and moods to get us to eat what they want, and often are driving us toward obesity.

Researchers concluded from a review of the recent scientific literature that microbes influence human eating behavior and dietary choices to favor consumption of the particular nutrients they grow best on, rather than simply passively living off whatever nutrients we choose to send their way. When you think about it though, this idea doesn’t seem to be too far fetched.

Bacterial species vary in the nutrients they need. What that means is that some for instance prefer fat, and others sugar. But here’s the creepy part, they not only vie with each other for food and to retain a niche within their ecosystem — our digestive tracts — they also often have different aims than we do when it comes to our own actions, that is of course, according to the study.

While it is unclear exactly how this occurs, the team believes this diverse community of microbes [collectively referred to as the gut microbiome] may influence our decisions by releasing signaling molecules into our gut. This alone might not send any red flags, but because the gut is linked to the immune system, the endocrine system and the nervous system, those signals could influence our physiologic and even our own behavioral responses.

“Bacteria within the gut are manipulative,” said Carlo Maley, PhD, director of the UCSF Center for Evolution and Cancer and corresponding author on the paper.” “There is a diversity of interests represented in the microbiome, some aligned with our own dietary goals, and others not.”

Thankfully we don’t have to let them win. We can influence the compatibility of these microscopic, single-celled houseguests by deliberating altering what we ingest, with measurable changes in the microbiome within just 24 hours of a diet change, an incredible turn around for sure.

“Our diets have a huge impact on microbial populations in the gut,” Maley said. “It’s a whole ecosystem, and it’s evolving on the time scale of minutes.”

Interestingly enough, there are even specialized bacteria that digest seaweed, found in people living in Japan, where seaweed is popular in the diet.

Research suggests that gut bacteria may be affecting our eating decisions in part by acting through the vagus nerve, which connects 100 million nerve cells from the digestive tract to the base of the brain. So really what happens in vagus, doesn’t really stay in vagus [You have no idea how long I’ve wanted to make that joke].

“Microbes have the capacity to manipulate behavior and mood through altering the neural signals in the vagus nerve, changing taste receptors, producing toxins to make us feel bad, and releasing chemical rewards to make us feel good,” said Aktipis, who is currently in the Arizona State University Department of Psychology.

Research has shown that in mice, certain strains of bacteria increase anxious behavior. It doesn’t stop there though, in humans, one clinical trial found that drinking a probiotic containing Lactobacillus casei improved mood in those who were feeling the lowest.

The team has also proposed further research to test the sway microbes hold over us. For example, would transplantation into the gut of the bacteria requiring a nutrient from seaweed lead the human host to eat more seaweed?

The speed with which the microbiome can change may be encouraging to those who seek to improve health by altering microbial populations. This may be accomplished through food and supplement choices, by ingesting specific bacterial species in the form of probiotics, or by killing targeted species with antibiotics. Optimizing the balance of power among bacterial species in our gut might allow us to lead less obese and healthier lives, according to the authors.

“Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating,” the authors wrote.

Not only could we find ways to help us control our behaviors, there are also other health issues at hand. For example, some of the bacteria that normally live within us cause stomach cancer and perhaps other cancers.

“Targeting the microbiome could open up possibilities for preventing a variety of disease from obesity and diabetes to cancers of the gastrointestinal tract. We are only beginning to scratch the surface of the importance of the microbiome for human health,” she said.

So next time you go to the kitchen because of that craving you’re having, remember it may not be your craving. Now if you’ll excuse me, there is a box of doughnuts with my name on them… good luck.

Sources: 
Alcock J, Maley CC, & Aktipis CA (2014). Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and potential mechanisms. BioEssays : news and reviews in molecular, cellular and developmental biology PMID: 25103109