Are You What Your Gut-Microbiome Wants You To Eat?

We’ve all heard the saying “you are what you eat,” but new microbiome research is shedding light on this old adage, with a more modern-day update being “you are what your gut-microbiome wants you to eat.” Let’s look at why this is the case.

First, we know that our food choices significantly impact our physical and mental health. As far back as the 1800s and 1900s, scientists hypothesized an apparent correlation between our food intake and the subsequent effects on appetite, body image, and brain function (Tzameli, 2013). Though biomedical research has already established the endocrine responses that regulate hunger and satiety in the gut-brain axis signaling, little attention has been paid to the mechanisms that influence an individual’s choice of food and nutrition.

Microorganisms that live in our gut may influence what we eat!

A growing body of evidence indicates that our gut microbiome may be one of the factors influencing our food choices. From Nutritional Psychology conceptualization, we are beginning to understand that eating behavior and food preferences are dependent on many aspects of the diet-mental health relationship (DMHR), such as our psychosocial environment, interoceptive experiences, sensory perception, cognitive processes, and psychological state. However, emerging research in the Microbiota-Gut Brain Axis (MGBA) suggests that the microorganisms residing within our gut may also influence what we eat. Therefore, the classic expression, “you are what you eat,” may soon be reframed as “you are [also] what your microbiome wants you to eat.”

A feedback loop between our gut microbiome, brain, and food choices.

To explore the influence of the gut microbiome on diet selection behavior, Trevelline and Kohl conducted an experiment in 2022 to study the influence of gut microbes on the diet selection behaviors in mice.

The classic expression, “you are what you eat,” may soon be reframed as “you are [also] what your microbiome wants you to eat.”

To achieve this, intestinal microbiota from three “donor” mouse species, each with distinct foraging behavior, were transplanted into germ-free “host” mice to colonize their intestinal tracts.

Following that, the donor germ-free mice were randomly divided into three treatment groups, each based on the donor species:

Carnivore (i.e., predatory-based)
Herbivore (i.e., plant-based)
Omnivore (i.e., inclusive-based)

The mice were then given a choice between a low protein-carbohydrate (LPC) diet and a high protein-carbohydrate (HPC) diet, and their diet preferences were tracked for 11 days. To assess the impact of the donor microbiome on host diet selection behavior, the researchers compared the microbiomes of mice in three treatment groups: predatory (carnivores), inclusive (omnivores), and plant-based (herbivores) (Fig 1A).

Figure 1A. Experimental design to assess host diet selection behaviors across different microbiomes. From Trevelline and Kohl, Proceedings of the National Academy of Sciences, 2022.

Strikingly, the authors discovered that when mice have given a choice of selected diets varying in macronutrient composition, each microbiome had a distinct effect on food choice behavior (Fig 1B). For example, host mice that received microbiota from herbivorous donors voluntarily ate fewer carbohydrates, evidenced by a higher protein:carbohydrate (P:C) ratio diet intake. On the other hand, omnivore and carnivore treatment groups chose a lower P:C ratio diet intake.

Given that these host mice had no microbiome prior to transplantation, the change in diet selection behavior is evidence of the microbiome influencing food choice (Alcock, 2014). Moreover, through an in-depth analysis of blood and fecal samples, the authors discovered the microbial release of essential amino acids (EAAs) from the gut microbiome of host mice, including tryptophan. Tryptophan is an important food choice driver because it is a precursor to serotonin, the happiness hormone that has been shown to regulate feeding behavior, metabolism, and diet selection (Harrold, 2012; Cryan, 2019; Kaur & Bose, 2019; Yabut, 2019; Gao, 2020; Trevelline & Kohl, 2022). Together, these findings show that the gut microbiome can influence host diet selection behavior by mediating the availability of EAAs.

The gut microbiome can influence host diet selection behavior by mediating the availability of Essential Amino Acids (EAAs).

Finally, the findings discussed here are of great interest to Nutritional Psychology. Together with other studies, they show us that what we eat can be influenced by our microbiota’s ‘bottom up’ connection. And in turn, this connection affects our food choices and dietary intake, which cycles back to influence our microbiota.

Figure 1B. Gut microbiome of donor mice altering feeding choices in host mice.

This reciprocal feedback loop is partly caused by the gut microbiome’s ability to synthesize EAAs, which interact with the gut-brain axis and, in turn, influence dietary habits. Depending on the food choices made, the body’s response to those choices can be beneficial or detrimental. Therefore, increasing awareness of the factors influencing dietary intake may help us to impact both our physical and mental health positively.

References

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Trevelline, B. K., & Kohl, K. D. (2022). The gut microbiome influences host diet selection behavior. Proceedings of the National Academy of Sciences of the United States of America, 119(17), e2117537119. https://doi.org/10.1073/pnas.2117537119

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