These diets are designed for specific purposes, with the aim of achieving your desired goal whether you know it or not, but do they have an effect on your gut microbiome?

What is the Ketogenic Diet? 

The keto diet is high in fat, low in carbs. This dietary approach should not be confused with a “low-carb” or “paleo” diet, in which more dietary carbohydrates are typically allowed and the body might not attain a state of nutritional ketosis.

With the keto diet, the goal is to get an individual’s body to the metabolic state of “ketosis.” This process happens when there is a drastic reduction of dietary carbohydrates. The body relies on glucose from carbohydrates as its primary energy source, but when it isn’t getting carbohydrates, it will switch over to burning fats instead. During this process, the body breaks down fats in the liver, which produces 

ketones, a type of acid, which then replaces glucose as the body’s primary energy source.

How the keto diet benefits the gut microbiome

The ketogenic diet is associated with increases in fecal short-chain fatty acids (SCFAs) and increases in Akkermansia muciniphila, a bacteria species that benefits gut health. These markers are associated with improved metabolic health, which include:1

Epilepsy: Although the ketogenic diet has been used for years to decrease seizure activity in epilepsy, the exact mechanism is not clearly understood.1 It is thought that the increases in SCFAs and serotonin production occurring in the gut microbiome are influential in inhibiting epileptic processes.2

Insulin resistance: An increased or decreased intake of carbohydrates has the biggest impact of macronutrients on the gut flora and its effect on insulin resistance.1

Obesity: The keto diet can increase the synthesis of microbial metabolites like SCFAs that can cross the blood-brain barrier and play a role in gut-brain communication.1 In this case, the research shows SCFAs signal to the brain through reward pathways and help a person suppress calorie intake, thus playing a role in weight management.

How a keto diet can hurt the gut microbiome

Decreased diversity: Research shows the keto diet can substantially decrease alpha diversity – the number of different bacterial species in the gut, which is generally undesirable.3

Low sustainability: Many individuals have successfully followed a ketogenic diet and achieved favorable outcomes. However, the diet takes diligence and an understanding of macronutrients and micronutrients. Its dietary restrictions can often lead to an inability to maintain the lifestyle.3

Increased risk for other health concerns: Research shows the keto diet – when not properly formulated – might be detrimental to health. In some instances, it can increase the risk of heart disease, nutrient deficiencies, disordered eating, or other health concerns.4 A keto diet might not be indicated for individuals who have conditions involving their pancreas, liver, thyroid, or gallbladder.

As always, if you’re unsure about whether a new diet is right for you, then consult with your health-care professional.

Paleo diet

The core concept behind the paleolithic diet, also known as the paleo diet, is to eat like the early humans from that era, avoiding processed and even farmed foods, and only eating foods that could be obtained by hunting and gathering. This means avoiding foods like sugar, dairy, and grains, and incorporating meats, seeds, nuts, and certain fruits and vegetables.

How a paleo diet benefits the gut microbiome

Short-term, smaller studies suggest the paleo diet can help manage weight loss, reduce blood pressure, and stabilize cholesterol levels.5

In addition, the paleo diet:

Minimizes the risk for certain diseases: Processed foods are loaded with sugars, sodium, and fats, as well as preservatives associated with the Western diet. These foods can stimulate chronic inflammation that can damage the gastrointestinal tract, reducing microbial diversity. The paleo diet, consisting of whole and unprocessed foods, eliminates processed foods and damaging additives, reducing potential disease risks.

Minimizes free radical damage: The paleo diet includes fruits and non-starchy vegetables – high in the antioxidants that protect cells from the damaging effects of free radicals. The paleo diet also contains essential fatty acids from fish and nuts that have anti-inflammatory activity.

Limits food known to cause gut sensitivity: Up to 20 percent of the world’s population experiences gut irritation from foods that contain gluten, dairy, or wheat. The paleo diet removes these foods, thus minimizing gut inflammation, allergies, and intolerances.6

Retains SCFAs: The paleo diet is associated with decreased excretion of SCFAs, which are byproducts of bacterial fermentation in the gut.6 Higher levels of fecal SCFAs mean the body is getting rid of these metabolites rather than using them, and higher fecal levels have been associated with gut dysbiosis, obesity, hypertension, and other cardiometabolic risk factors.

How it can hurt the gut microbiome

Despite the positive impacts on the body, the paleo diet does have drawbacks. Research shows this diet can be associated with:

A possible increased risk of cardiovascular disease: Individuals following the diet, particularly if they eat a lot of red meat or saturated fats can have higher levels of serum TMAO, a metabolite produced when the gut bacteria metabolize red meat. Researchers suspect elevated levels of the bacteria Hungatella in the gut is what drives TMAO production. High levels of TMAO are associated with an increased risk of cardiovascular disease.7

Lower Bifidobacterium and Roseburia abundance: Both bacteria species are known for their health benefits and have been found to be reduced in individuals who follow the paleo diet.7 This might be due to the lower overall fiber and higher fat content of the diet. Bifidobacterium, in particular, is known to produce beneficial metabolites, like the SCFA butyrate, when fermenting carbohydrates.7

The takeaway

Although both diets can positively impact your metabolic health and gut microbiota, evidence shows there are downsides.

As the authors of many studies suggest, the long-term effects of the paleo and keto diets need further research. And everyone responds to these diets differently due to genetics, lifestyle, and health conditions. No matter the diet, it is important to have a well-formulated plan and consider the variety of food options that will meet the intended macro- and micronutrient regimen.

Before committing to a new diet, consider taking Thorne’s Gut Health Test. This easy-to-do, at-home test provides a detailed analysis of the state of your gut health and gives you personalized recommendations to improve your scores. 

References

  1. Attaye I, van Oppenraaij S, Warmbrunn MV, Nieuwdorp M. The role of the gut microbiota on the beneficial effects of ketogenic diets. Nutrients 2021;14(1). doi:10.3390/nu14010191
  2. Ding M, Lang Y, Shu H, et al. Microbiota-gut-brain axis and epilepsy: A review on mechanisms and potential therapeutics. Front Immunol 2021;12:742449.
  3. Batch JT, Lamsal SP, Adkins M, et al. Advantages and disadvantages of the ketogenic diet: A review article. Cureus. 2020;12(8):e9639.
  4. Helms N. Is the keto diet safe? What are the risks? Published January 3, 2023. https://www.uchicagomedicine.org/forefront/health-and-wellness-articles/ketogenic-diet-what-are-the-risks [Accessed September 6, 2023.]
  5. Paleo diet: Eat like a hunter-gatherer and lose weight? Mayo Clinic. Published October 20, 2022. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/paleo-diet/art-20111182 [Accessed September 6, 2023.]
  6. Whalen KA, McCullough ML, Flanders WD, et al. Paleolithic and Mediterranean diet pattern scores are inversely associated with biomarkers of inflammation and oxidative balance in adults. J Nutr 2016;146(6):1217-1226.
  7. Genoni A, Christophersen CT, Lo J, et al. Long-term Paleolithic diet is associated with lower resistant starch intake, different gut microbiota composition and increased serum TMAO concentrations. Eur J Nutr 2020;59(5):1845-1858.