If you’re a sci-fi movie fan, you know this scene: an alien life form, or bacteria, gets into the body of a human host and takes over their brain. Scary, yes… but what if this scenario wasn’t completely so far-fetched? What if you could actually blame your decision to have those two extra slices of chocolate cake on the appetites of millions of little gut microbiota taking over your body?
Is your gut bacteria masterminding your food cravings? Possibly. First, let’s investigate…
The Gut-Brain Axis
Research is plentiful into what’s known as the “gut-brain axis,” as scientists have come to better understand the strong link between our guts and our brains. What is becoming very clear is that the functions of our gut bacteria – or human gut microbiome – are more far-reaching than any of us could ever imagine.
Your brain and your gastrointestinal system are linked via something called your “vagus nerve,” the longest of your cranial nerves. And there now appears to be strong evidence that gut microorganisms can activate that vagus nerve, affecting your brain and your behavior.
Researchers believe that these bacteria may influence dark moods, anxiety, and even developmental disorders.1,2
But now they also think these gut bacteria could be telling our brains what to eat – and not always in a positive, “nutritional coach” kind of way.
They may be influencing eating in ways that favor their own well-being, at the expense of the host’s fitness (the “host” being us).3
What We Know
Evidence now suggests that we may be only about 43 percent human – that is, we are made up of about 43 percent human cells – the rest are microbial cells. If that doesn’t make you want to run and hide under your pillow, here’s another one: Our human “instruction system,” or genome, is made up of around 20,000 genes – but our microbiome contributes somewhere between 2 and 20 million genes.4
On the flip side, some scientists believe that our microbiome may actually be another human organ, because of all its important functions.5
All these different microbes compete for nutrients – and survival – and it’s thought that the more dominant ones may wield the most power over the brain.
Each time you eat, you increase the population of some types of bacteria in your gut, and you minimize other types. As the numbers of each microbiota change, they activate different genes, absorb different nutrients, and begin to influence your dietary cravings.6
So, a lower diversity in your gut microbiome could be associated with more unhealthy eating behavior as the dominant microbes take over.
In fact, it’s been shown that people who crave chocolate have different microbial metabolites in their urine than those who are ambivalent to that sweet, creamy taste. Research shows this is true even if the people were following the exact same diets.7
The idea here is that bacteria also have food preferences. Some bacteria appear to have a rather strong love for fats and sugars. So, they may exert their influence by making certain foods taste better, by releasing hunger-inducing hormones, or by manipulating that vagus nerve to control your eating behavior.8
But you do have some control. In a kind of chicken-or-the-egg scenario, you can also influence your gut flora by choosing the right kinds of foods to eat. It’s a two-way street. Don’t you always find that when you eat a consistently healthy diet, you tend to crave and seek out more of the same healthy foods?
But There’s More…
Neuroscientists in Lisbon recently sought to unravel this mystery further by studying the eating behaviors of Drosophila melanogaster, a type of fruit fly. They found that specific types of gut flora help a host detect which nutrients are missing in the diet through cravings. So, they influence the appetite and, ultimately, the health of the host.
In this case, the bacteria introduced was “good bacteria,” which made good dietary decisions on behalf of the fruit fly host. They even went so far as to help the host to compensate when it was low on essential nutrients, like amino acids.9
How To Fight Back
Of course, you want to control persistent cravings and prevent bad eating behaviors. How can you do this? By fighting back against your own gut microbiota, the ones that seek to manipulate you into unhealthy eating patterns. Here’s how to maintain (and boost) your gut health:
1. Increase Probiotic Foods
The World Health Organization defines probiotics as, “live microorganisms which when administered in adequate amounts confer a health benefit on the host.”10 Probiotics can help inhibit “bad” bacterias and stabilize the good bacteria living in your colon. But probiotics can’t change your gut permanently, so you need a regular intake of probiotic foods (or supplements) for continued benefits.
Foods which contain high levels of live, healthy, “good” microorganisms include fermented foods, like natural yogurt, sauerkraut, pickles, miso, Kefir-style drinks, sourdough bread, and kombucha. Certain soft fermented cheeses, like cheddar, feta, and Gouda are also good choices.
2. Increase Prebiotic Foods
Prebiotics come from the types of fiber that humans can’t digest. But the beneficial bacteria in your gut love this fiber. Prebiotics can help increase the growth of more good bacteria in your gut.
Top food choices for increasing your natural prebiotics include chickpeas, lentils, garlic, barley and rye, pistachios, nectarines, watermelon, dried figs, leeks, beets, and snow peas.11
3. Diversify Your Diet
If diverse gut flora equals a healthy gut, then isn’t it time to start diversifying your diet? If you live on foods high in fats and sugar, then that will be reflected in the kinds of microbiota living in your gut. A diverse diet can keep the “balance in the house” so to speak, with no single bacteria able to cause a mutiny.
While there is still much more to be discovered about the gut-brain connection and the role that the gut microbiome plays in human health, these discoveries are quite incredible. When you think about it, you really are just a mass of microorganisms housed in a human frame. Feed those microorganisms well, and you’ll reap the benefits!