Inflammation

Plant-based diets bring inflammation down

By WhyStopHarmingAnimals.com

Chronic low-grade inflammation is a common thread in heart disease, diabetes and frailty. The usual way to measure it is C-reactive protein, or CRP, a standard blood marker of background inflammation. CRP runs lower in people who eat vegetarian and vegan diets[3][4][5][6], and randomized trials show that moving people onto plants brings it down[1][2].

The trial evidence

In 2026 a University of Warwick team published the first systematic review of randomized trials on plant-based diets and CRP, in Nutrition, Metabolism and Cardiovascular Diseases[1]. Across 541 people, vegan, vegetarian and whole-food plant-based diets cut CRP by about 1.13 mg/L compared with omnivorous diets[1]. The trials were small, but because participants were assigned their diets[1], the result doesn’t rest on food-frequency questionnaires or on the kind of person who chooses to go vegan.

Sutliffe and colleagues found the same direction in a vegan lifestyle intervention reported in Complementary Therapies in Medicine in 2015: CRP fell[2].

Reviews of the observational studies

The larger body of observational work agrees[3][4]. Craddock’s 2019 systematic review and meta-analysis in Advances in Nutrition found vegetarian-based patterns linked with lower CRP, lower fibrinogen and a lower total white-cell count[3], three separate measures of the same underlying process.

Haghighatdoost’s 2017 meta-analysis in Public Health Nutrition added a time dimension[4]. People who had followed a vegetarian diet for at least two years had lower high-sensitivity CRP than non-vegetarians[4]. Duration mattered, so a few weeks of eating better won’t show up the way years of it do[4].

Among Adventists, Jaceldo-Siegl and colleagues found vegetarians had lower CRP and lower IL-6, another inflammatory signal[5]. Body weight explained part of that gap[5]. Weight is one route by which diet affects inflammation, but across the inflammation studies it isn’t the only one[5].

Vegans lowest, and food quality counts

In 2025 Mrozik and colleagues compared vegans, vegetarians and omnivores directly[6]. Vegans had substantially lower hs-CRP than both other groups, and omnivores had higher IL-6 and higher white-cell counts[6]. The same study found that the quality of the plant foods mattered too[6]. A separate study of vegans and vegetarians in urban Poland made the point more bluntly: inflammation markers tracked with diet quality, beyond the vegan or vegetarian label itself[7]. The benefit comes from foods like beans, vegetables and whole grains, and a diet built on vegan ice cream won’t deliver it. Both studies are observational.

One route from meat to inflamed arteries

Koeth and colleagues at Cleveland Clinic, writing in Nature Medicine in 2013, traced one mechanism[8]. Gut bacteria turn L-carnitine from red meat into TMAO, a compound that promotes atherosclerosis[8]. When the researchers gave people a carnitine meal, omnivores produced far more TMAO than vegans and vegetarians[8]. A meat eater’s gut bacteria have been trained on meat and handle it differently[8], while a vegan’s gut makes little TMAO from the same meal[8].

What the evidence can and can’t say

The strongest result here comes from the trials in the Warwick meta-analysis, where people were assigned a diet and CRP fell[1]. The trials were few and small, and CRP is a marker of inflammation, not a disease outcome in itself. The reviews by Craddock and Haghighatdoost, the Adventist data and the Mrozik and Poland[7] comparisons are observational, so they describe who has lower inflammation[3][4][5][6] without proving the diet caused it. The Adventist work shows that some of the gap runs through lower body weight[5].

Taken together, though, the designs support each other. The observational studies find lower CRP[3][5][6], fibrinogen[3], IL-6[5][6] and white-cell counts[3][6] in people who don’t eat animals, with vegans lowest[6]. The trials show CRP falling when people switch[1][2]. The TMAO work gives one concrete route from red meat to damaged arteries[8]. And the quality studies show where the benefit comes from: whole plant foods, eaten for years[4][6][7].

Because chronic low-grade inflammation sits underneath heart disease, diabetes and frailty, a diet that keeps it lower[1][3] is doing work well beyond any single blood test.