• A new study from researchers at the National Institutes of Health in the United States has found significant immune-system responses to ketogenic and vegan diets.
  • Participants followed both diets for two weeks each. The keto diet was found to prompt responses associated with pathogen-specific immunity developed through regular exposure and vaccines.
  • The vegan diet elicited responses rooted in innate immunity, the body’s first line of defense against pathogens.

A new study from researchers at the National Institutes of Health has found significant immune-system responses to ketogenic and vegan diets.

By performing “a multiomics approach including multidimensional flow cytometry, transcriptomic, proteomic, metabolomic and metagenomic datasets,” the researchers were able to assess how 20 participants’ bodies responded to two weeks each of the ketogenic and vegan dietary regimes.

The ketogenic diet prompted responses associated with adaptive immunity — pathogen-specific immunity that is developed through regular exposure and vaccines — while the vegan diet elicited responses rooted in innate immunity, which is the body’s first line of defense against pathogens.

There were also significant changes in the microbiomes of the participants, specifically the abundance of the gut bacteria associated with each diet. The ketogenic diets seemed to lead to a reduction in amino acid metabolism within their microbiomes, perhaps as a result of the larger amount of amino acids in that diet.

Each participant was allowed to eat as much as they wanted during the two weeks they were adhering to each diet.

When people were on the vegan diet, which contained about 10% fat and 75% carbohydrates, they consumed fewer calories than their counterparts on the keto diet, which was made of about 76% fat and 10% carbohydrates.

Given the random application of the order of the diets and the diversity of the participants in age, race, gender, ethnicity, and body mass index (BMI), the study’s authors point to how these diets can be consistently applied to the body’s pathways with somewhat predictable results.

“Further exploration of functional trade-offs associated with each diet would be an important line of research,” they write in the study.

Kristin Kirkpatrick, MS, a registered dietician at the Cleveland Clinic Department of Department of Wellness & Preventive Medicine in Ohio and a senior fellow at the Meadows Behavioral Healthcare in Wickenburg, Arizona, told Medical News Today that while these varied diets do show effects on overall health, there is a number of other factors that are at play.

“Both dietary patterns varied in their content of fat, fiber, carbohydrate, and protein composition and each approach had variations of change to immune function,” said Kirkpatrick, who wasn’t involved in the study. “Genetics, and specifically, nutrigenomics may help in determining the correct overall dietary pattern for an individual in addition to factors such as personal, religious, and cultural preferences. There is no one-size-fits-all all approach to diet and even though these two diets may appear to some to have extremes on both ends, there appear to be certain factors of each that are impacting immune function. This was also a small study so larger studies may be warranted to further assess results.”

The ketogenic diet, known as keto, focuses on foods that provide a lot of healthy fats, adequate amounts of protein, and few carbohydrates.

By depleting the body’s sugar reserves and getting more calories from fat than from carbs, the diet works by forcing the body to break down fat for energy. This results in the production of molecules called ketones that the body uses for fuel and can stimulate weight loss.

After undergoing the ketogenic diet, participants in the NIH study were found to have an up-regulation of pathways linked to adaptive immunity, including T cell activation and enrichment of B cells and plasma cells. One of those pathways, oxidative phosphorylation, which is associated with T cell activation and memory formation, was improved after the ketogenic diet compared with the aftereffects of a vegan or baseline diet.

Analysis of participants’ proteomes — the entire set of proteins one organism produces — also indicated that the ketogenic diet may have a bigger impact on protein secretion than a vegan diet, with impacted proteins predicted to originate from several tissues, including the blood, brain, and bone marrow. Both diets affected proteins predicted to originate from the liver and secondary lymphoid organs.

The vegan diet eliminates all animal products, including meat, eggs, and dairy.

It has been associated with weight loss, improved heart health, and a reduction in the risk of chronic diseases such as cancer and type 2 diabetes. It is heavy on fruits, vegetables, beans, nuts, and seeds.

The study’s authors reported that the vegan diet resulted in a significant up-regulation of the production of red blood cells (erythropoiesis) and heme metabolism. Heme regulates transcription and protein synthesis during erythropoiesis. And the vegan diet resulted in more dietary iron (also important to erythropoiesis) being ingested in the vegan diet than in the ketogenic diet.

Matthew Carter, a doctoral student at the Sonnenberg Lab in the Department of Microbiology and Immunology at Stanford University in California (which recently published the results of a human dietary intervention trial comparing a high-fiber diet to a high-fermented foods diet), told Medical News Today that the vegan diet raised some questions about how it affected the immune system vs the ketogenic protocols.

“The authors do speculate that part of these differences might be caused by differences in caloric intake (vegans consumed fewer calories),” Carter said. “So it’s a little hard to see if there was something in particular in the vegan diet that caused these changes, or if something about eating less caused these changes. There are some interesting studies on fasting that have also shown changes to the innate and adaptive immune systems.”

Kirkpatrick noted that while the study’s findings support how powerful a role diet plays in immune function and microbiome health, the rigors of these particular diets can be difficult.

“Many of my patients have benefited from both vegan dietary patterns as well as keto dietary patterns,” Kirkpatrick said. “However, I have also seen challenges with both in terms of long-term sustainability. For example, few of my patients can remain strict keto over 6 months, and many transition to a low to moderate carb approach.”

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