Plant-based diets may lower inflammation marker, University of Warwick study finds

Plant-based diets may help reduce systemic inflammation, according to new research led by University of Warwick scientists that analyzed clinical trials measuring the effect of dietary patterns on C-reactive protein, a widely used marker of inflammation and cardiovascular risk.

• University of Warwick researchers analyzed seven randomized controlled trials involving 541 participants.
• Plant-based diets were associated with an average 1.13 mg/L reduction in C-reactive protein levels.
• Researchers called for larger trials to confirm the findings and strengthen the evidence base.

The study, published in Nutrition, Metabolism and Cardiovascular Diseases, was described as the first systematic review and meta-analysis of randomized controlled trials to assess whether plant-based dietary patterns influenced C-reactive protein, or CRP. The trials included vegan, vegetarian, and wholefood plant-based diets, which were compared with omnivorous diets.

CRP is commonly used as an indicator of systemic inflammation in the body. Chronic low-grade inflammation, sometimes referred to as inflammageing, has been increasingly recognized as a contributor to age-related disease, including cardiovascular disease, type 2 diabetes, and some cancers.

The Warwick-led team initially identified nearly 3,000 studies that measured plant-based diets and CRP. However, only seven met the researchers’ criteria for inclusion as randomized controlled trials. Those studies included a combined 541 participants.

“We found that consuming a plant-based diet instead of an omnivorous diet reduced CRP levels by 1.13 mg/L on average,” said Luke Bell, lead author and a student at Warwick Medical School. “CRP is one of the body’s main signals of inflammation, and lower levels generally indicate less background inflammation circulating in the body.

“CRP levels are also commonly used to assess cardiovascular risk, with levels below 1 mg/L considered low risk and above 3 mg/L high risk. Therefore, a CRP reduction of the magnitude found in our study could move individuals into lower risk categories.”

Plant-based diets are generally rich in fruits, vegetables, whole grains, legumes, nuts, and seeds. They also tend to provide higher levels of fiber, antioxidants, and unsaturated fats than diets containing more animal products. The researchers suggested that these nutrients, along with lower saturated fat intake, may help explain the observed anti-inflammatory effect.

Joshua Gibbs, co-author and project supervisor at Warwick, said the findings may point to another mechanism through which plant-based diets support long-term health.

“Plant-based diets are already known to improve key cardiovascular risk factors such as blood pressure, LDL cholesterol, and body weight,” Gibbs said. “Our findings suggest an additional pathway through which these diets may reduce chronic disease risk.

“When studies that included structured exercise programmes were excluded, the reduction remained, although slightly smaller. The largest reductions were seen in studies that combined plant-based diets with increased physical activity, suggesting lifestyle changes may have the greatest impact when adopted together, although more research is needed to confirm this.”

Previous observational research has linked plant-based diets with lower inflammation and reduced chronic disease risk. However, the Warwick study focused only on randomized controlled trials, which are considered a stronger study design for assessing cause and effect than observational research.

The authors also cautioned that the evidence base remains limited. Professor Francesco Cappuccio, co-author at Warwick Medical School, noted that only a small number of trials met the review’s criteria.

“It is worth bearing in mind that of the nearly 3,000 studies identified for this study, only seven met the inclusion criteria for randomised controlled trials,” Cappuccio said. “Although the results suggest a plausible effect of plant-based food in reducing inflammation, given the paucity of large trials, we should encourage more robust evidence to support these early findings.”

The paper, The effect of plant-based dietary patterns on C-reactive protein: A systematic review and meta-analysis of randomised controlled trials, was published in Nutrition, Metabolism and Cardiovascular Diseases.