Study: Vegan or keto diet rapidly impacts immune system

A groundbreaking study published in Nature Medicine unveils the profound effects of structured diets on immune function.

The findings were based on an analysis of a clinical trial that required subjects to consume both a vegan and ketogenic diet each for two weeks. Researchers revealed the keto diet improved markers of adaptive immune function, while the vegan diet led to improvements in innate immune function.

Structured diets, like vegan and ketogenic diets, have become more popular in recent years. More than half of Americans reported following a diet or eating pattern in 2022 — an increase of 13% compared to the year prior. Plant-based eating was among the top eating patterns adopted by Americans.

Protecting long-term health was the leading reason cited by Americans for following a specific diet or eating pattern. The present study provides encouraging findings for those seeking to adopt a specific diet pattern for better health.

“Uncovering the principles by which nutrition regulates immunity in humans could greatly improve our ability to design personalized nutritional interventions that prevent and treat disease,” authors of the article wrote.

For the clinical study, 20 participants sequentially followed two distinct diet patterns — a low-carbohydrate keto diet and a low-fat vegan diet — for two weeks. The diet changes were assigned in random order. There was no washout period between diets.

While the nutrient intake between the two diets varied significantly, the diets shared a foundation of nonstarchy vegetables with small amounts of digestible carbohydrates and minimum amounts of highly processed food. Compared to the keto diet, the vegan diet was high in dietary fiber and low in dietary sugars. The keto diet was higher in fatty acids and amino acids compared to the vegan diet.

To assess the impact of each diet on immunity, the researchers of the study analyzed data that spanned different omics groups, including transcriptomic, proteomic, metabolomic and metagenomic data sets. The researchers called the method of analysis a “multiomics” approach.

Both diets had a positive impact on immune health, the study found. How each diet affected the immune system, however, differed.

Per researchers, the keto diet significantly upregulated the pathways of the adaptive immune system. A keto diet also caused an enrichment in cells associated with the adaptive immune system.

Conversely, a vegan diet significantly impacted the innate immune system by upregulating pathways associated with antiviral immunity.

Importantly, researchers noted abrupt, significant changes in markers of immune health independent of which diet participants adopted first — possibly the result of decreased processed food intake, they reported.

“Whether these changes resulted from the shift in diet or an abrupt decrease in the consumption of highly processed food, which is often represented in a standard Western diet, remains unclear but would be of interest for future investigation,” the researchers wrote.

In addition to immunity, researchers evaluated the impact of the diets on the participants’ microbiota. They found both diets significantly affected the microbiome in different ways, but they noted a ketogenic diet caused strong downregulation of most microbial pathways compared to a vegan diet and baseline.