You know that saying, your body craves what your body needs? We may need to revise it to “your body craves what your gut bacteria need.”
Scientific discovery is starting to crack open the door to the mysterious world of what lives in our intestines. More complex than bacteria happily munching on our food or causing an embarrassing bathroom run, our gut bacteria have harbored a little secret. They could have a part in driving our food choices, sending messages to our brains to dictate what we gravitate towards in our food – all to benefit their survival.
It's an eerie suggestion that something other than our free will drives our food choices. It sounds like science fiction of a nasty virus setting up shop in its host because, for many years, we were comfortable thinking of our gut as no more complicated than a squeezing tube. It's so far down on our health priorities that we only pay attention when we have a rather embarrassing emergency and must dash to the toilet. Despite everything we know about our bodies, the world around us, and even the universe and the ocean's depths, we have only really dived into the complex world of the gut in the last decade, and it's fascinating. Scientists are becoming interested in this nascent world of discovery, and research is beginning to point toward a symbiotic relationship with those inside us.
Let's look into what they have found so far and the practical ways you can help be a gracious host to your guests.
A microbial organ
The human body has trillions of cells, as many gastrointestinal bacteria live in our gastrointestinal tract alone. Because of this intense density of colonized creatures, it's worth looking at the gut as a microbial organ rather than something we own and operate ourselves. There are so many different types of microbiotas that they have classified them the same way we would with animals in the wild, according to phyla, classes, orders, families, genera, and species. According to an article called "What is the Healthy Gut Microbiota Composition? A Changing Ecosystem across Age, Environment, Diet, and Diseases," more than 160 phyla and 200 species exist. However, the two most dominant ones, Firmicutes and Bacteroides comprise 90% of our gut bacteria.
These bacteria don't just hang around. They have substantial roles in our bodies; they help us digest our foods, regulate our immune system, wage wars against other bacteria that cause disease, and even produce vitamins that our bodies use.
What's the perfect mix?
If we were to try and determine what was the perfect makeup of all these bacteria, we would never be able to. The volume and makeup of individual phyla and species are so vast among individuals living in the same household that giving a healthy gut profile is impossible. Our microbiota is as unique as our fingerprints. They are also easy to manipulate by our unintended exposure to things like chlorinated water, food additives, and pollutants. Additionally, we can dramatically impact our microbiota diversity through our lifestyle, the foods we eat, the antibiotics we take, and even our exercise.
This means every action we take as individuals; we are rebalancing the equation of good versus harmful bacteria and redefining how much of what species are in our gut. This knowledge is compelling; it means that whatever we put in our mouths holds great importance to the world inside us.
The thing with cravings…
We already know that our gut bacteria eat the food we eat, and when we eat processed foods that have simple sugars, our bacteria are delighted. Sometimes these not-so-beneficial bacteria flourish because of our food choices. However, scientists are beginning to realize that some little critters do not have a penchant for sweet things, which may influence cravings to get what they want.
We've also known for quite some time that the gut does communicate with the brain. Researchers at the University of Pittsburg tell us that tryptophan, an amino acid we eat, is also produced in the gut. Tryptophan can reach the brain and convert to serotonin, which tells us we are satiated. Later, it can turn into melatonin to tell us we are sleepy. That's excellent communication if you ask me.
So, if our bacteria eat what we eat and signal the brain about our food intake, imagining that they start requesting pieces of cake is perhaps not all as crazy as we once thought. Researchers at the California Institute of Technology (Caltech) found that mice with microbiotas disrupted by antibiotics consumed up to 50% more sugar than mice with typical bacteria levels. One of the researchers, Professor Mazmanian, said "it has been known for a decade that diet shapes the composition of the gut microbiome, but whether bacteria in the intestines influence feeding behaviors remains largely unexplored" He continues further to say, "we identified that the underlying reason for this outcome was not nutritional, but rather a behavioral motivation to eat more of a desirable food when gut bacteria is missing, and performed initial analysis to validate changes in brain activity."
A new study on mice from the University of Pittsburg, as reported by Scientific American, showed that mice with altered gut microbiomes started to select foods significantly different in macronutrients. Mice with microbes from herbivorous wild rodents chose diets with higher protein-to-carbohydrate ratios, and those microbes from carnivorous rodents chose a lower protein-to-carbohydrate ratio.
In response to this study, Jane Foster, a neuroscientist at McMaster University in Ontario, said, "the findings show there is a unique pathway that has coevolved between animals and the resident bacteria in their gut, and there is a bottom-up communication about diet."
As interesting as this research is, even the researchers quickly point out that you can't blame all your cravings on your unruly guests; there is not enough information. So far, the main subjects have been mice and fruit flies, and humans have much more complicated guts. So next time you want to use this argument for a second slice of cake, it won't work. There is much work to be done to determine how this works.
There is so much to know, and I want to know everything. I can't wait for the research to continue.
How you can improve your gut microbiota
The one thing we know about gut microbiota is that the more diverse it is, the healthier it is. You can have diverse bacteria by eating high-fiber fruits and vegetables and consuming lots of fermented probiotics (kimchi, sauerkraut, curd) and prebiotic foods (barley, garlic, onions, bananas). Make these an integral part of your diet, rather than subsisting on a sprig of parsley as your vegetable quotient at meal times. Your gut and healthy bacteria will thank you for the healthy, nutritious food.
Secondly, limit the amount of junk food and sugary treats that unbeneficial bacteria love. By starving these bacteria of the foods they love, there is no reason for them to stick around, is there?
And finally, exercise has been found to increase the bacterial diversity in our guts – so let's get out and get moving!