How Dietary Protein May Impact the Gut Microbiome
We know that a high-fiber diet and fermented foods help keep your gut microbiome flourishing, but did you know that protein sources may also impact it? 1 New research from North Carolina University suggests that protein in an animal’s diet may affect the population as well as the function of the microbiome. This research may lead to a better comprehension of how to prevent and treat gastrointestinal conditions that affect the quality of life of millions of people worldwide. 2
Alfredo Blakeley-Ruiz, an NC State postdoctoral researcher and co-corresponding author of a paper describing the study notes, "There's something wrong with what we're eating today, and we are not close to knowing what that is. Our lab wanted to know how different diets impact what lives in the gut, and to learn something about what those microbes are doing, functionally, in response to that diet."
The researchers were curious about how the source of protein in the diet impacted the gut microbiome of mice. Proteins in milk, eggs, and plant-based proteins like pea or soy were compared. Mice consumed diets with only one source of protein for a week each time, including egg whites, brown rice, soy, and yeast.
A technique using high-resolution mass spectrometry discovered that the gut microbiome of the mice was altered quite a bit during the course of the study. Some protein sources exhibited extreme effects.
According to Blakeley-Ruiz, "The composition of the gut microbiome significantly changed every time we changed the protein source. The protein sources with the biggest functional effects were brown rice, yeast, and egg whites."
When evaluating the functional changes of the gut microbiome, the study discovered that the largest impact of dietary protein included amino acid metabolism and degradation of complex sugars.
"Brown rice and egg white diets increased amino acid degradation in the mouse gut microbiome, meaning that the microbes were breaking down those proteins instead of making their own amino acids from scratch," Blakeley-Ruiz said. "This makes intuitive sense because proteins are made of amino acids, but this is something we want to dig into more. Some amino acids can degrade into toxins and others can impact the gut-brain axis, so there are potential health implications from these diets."
In addition, the study showed that long chains of sugars attached to the dietary proteins, called glycans, play a role in altering gut microbiome function. Several dietary protein sources, including soy, rice, yeast, and egg white, caused microbes in the gut to change the production of enzymes that break down glycans, sometimes significantly.
Blakely-Ruize believes this could be significant health-wise. "In the egg white diet, in particular, one bacterium took over and activated a bunch of glycan-degrading enzymes. We then grew this bacterium in the lab, and found that the glycan-degrading enzymes it produced in media containing egg white protein were similar to those produced in media containing mucin."
A compound that lines the inside of the gut known as mucin, protects the digestive system from hydrochloric acid and pathogens. If bacteria make enzymes that purposely or accidentally destroy mucin, the lining of the intestinal wall could be destroyed, leading to negative effects on gut health.
Blakely-Ruiz notes that future research on the connection between the expression of glycan-degrading enzymes in egg whites and the destruction of mucin by gut bacteria needs to be explored.
NC State associate professor of plant and microbial biology and co-corresponding author of the paper, Manuel Kleiner, said the study lays the groundwork for future investigation of the effects of protein sources on the gut microbiome.
He notes that a limitation of the study was that the diets were artificial and could produce amplified results. However, they discovered that egg whites have extreme impacts on the gut microbiome. They’re curious to see what the process of this effect is in a mixed protein diet in mice.
"Our study shows not only which bacterial species are in the gut microbiome and their abundance, but also what they are actually doing. Here, they are specifically digesting the glycans. The result is a very comprehensive picture of what really matters in the gut in terms of diet and function."
Don’t toss your egg whites out! More research is needed, especially in humans.
Below are 10 ways to keep your gut microbiome happy and health:
· Include whole grains in your diet such as rolled oats, whole grain breads, cereals, and pasta, brown rice, farro, and other whole grains.
· Eat beans and legumes regularly to meet your fiber needs. A half cup of most legumes provides over 20% of the Daily Value for fiber.
· Enjoy fresh or frozen fruits regularly.
· Add fermented foods to your diet including kimchi, miso, and sauerkraut. 3
· Try kefir in your breakfast cereal in place of milk for probiotics.
· Add fresh or frozen fruit to yogurt or eat yogurt on its own.
· Avoid ultraprocessed red meat, fast food, fried and high-sugar snacks.
· Get plenty of sleep. Poor sleep may affect your gut microbiome. 4
· Exercise regularly. This also keeps your gut microbiome in top shape. 5
· Limit alcohol consumption. Excess alcohol impairs the gut microbiome over time. 6
Lisa Andrews, MEd, RD, LD
References:
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Souza PB, de Araujo Borba L, Castro de Jesus L, Valverde AP, Gil-Mohapel J, Rodrigues ALS. Major Depressive Disorder and Gut Microbiota: Role of Physical Exercise. Int J Mol Sci. 2023 Nov 28;24(23):16870. doi: 10.3390/ijms242316870. PMID: 38069198; PMCID: PMC10706777.
Hsu CL, Schnabl B. The gut-liver axis and gut microbiota in health and liver disease. Nat Rev Microbiol. 2023 Nov;21(11):719-733. doi: 10.1038/s41579-023-00904-3. Epub 2023 Jun 14. PMID: 37316582; PMCID: PMC10794111.
