The fight for your attention

Cravings for a doughnut might be blamed on the microbiome (Photo: Makoto Satsukawa)

Cravings for a doughnut might be blamed on the microbiome (Photo: Makoto Satsukawa)

You’re working along doing your usual stuff and suddenly you feel a hunger pang. And you don’t just feel hungry, you crave fatty food. If you had a Krispy Kreme doughnut ready you would gulp it down. But fortunately there is none within reach. There are conflicting signals and you change your mind. Now you have a craving for sugar and you stretch for the Coke. You know you shouldn’t but you still do it. What’s happening here?

Your microbiome at work

You remember the microbiome we have written about in previous blogs, the 100 trillion bacteria in your gut that outnumber your own cells about 100-fold? They help breaking down your food, fighting off infections and nurturing your immune system. It’s a lovely, invisible garden that play a crucial role in your well-being. However, even if it sounds like science fiction, it seems they are not content with limiting their activity to the gut, but may very well affect both your cravings and mood to get you to eat what they want.

Bacterial species vary in the nutrients they need. What that means is that some for instance prefer fat, and others sugar. The creepy part is that they not only vie with each other for the food they need to try to retain a niche within the digestive tract, they also try to make sure that you select the food they need. Different species of microbes thrive on different kinds of food. If they can prompt us to eat more of the food they depend on, they can multiply.

Researchers in reviewing the recent scientific literature concluded that microbes in the microbiome influence human eating behaviour and dietary choice to favour consumption of the particular nutrients they grow best on, rather than simply passively living off whatever nutrients you choose to send their way. There is a diversity of interests represented in the microbiome, some aligned with our own dietary goals, and others not. Of course it makes sense for them, but the question is how they have the means to influence what you eat.

Signalling systems at work

While it is unclear exactly how this occurs, the research team believes this diverse community of microbes 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 your physiologic and even your own behavioural responses.

Research suggests that gut bacteria may be affecting your 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. Microbes have the capacity to alter the neural signals in the vagus nerve, changing taste receptors, producing toxins to make you feel bad, and releasing chemical rewards to make you feel good.

Who is the puppet master?

Who is the puppet master? (Photo: Luc De Leeuw)

Who is the puppet master? (Photo: Luc De Leeuw)

Fortunately, it’s not a one-way street. In turn your own diet choice will have a huge impact on the microbial population in your gut. It’s a whole ecosystem, and it’s evolving on the time scale of minutes. You can influence the composition of the microbiome by deliberately change what you eat, with measurable changes in the microbiome within 24 hours of a diet change.

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. Because the microbiome is easily manipulated by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota might offer a possible approach to otherwise difficult problems of obesity and unhealthy eating. Optimising the balance of power among bacterial species in our gut might allow us to fight obesity and live more healthier lives.

We are only beginning to scratch the surface of the importance of the microbiome for human health. Targeting the microbiome could open up possibilities for preventing a variety of diseases from obesity and diabetes to cancers of the digestive tract. Although it is early days, it might pay off to attempt to be in charge of what you eat, now when you know the sneaky impact of your own bugs. Try to be your own puppet master.

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