A Plant-Based Diet Can Prevent Inflammation

Being overweight or obese is often associated with chronic inflammation, which increases the risk of cardiovascular disease, type 2 diabetes and cancer. A team of scientists led by Krasimira Aleksandrova and Fabian Eichelmann of the German Institute of Human Nutrition (DIfE), a DZD partner, has now analyzed 29 scientific studies that investigated the effects of a plant-based diet on the inflammatory marker levels of overweight people. As the meta-analysis* published in Obesity Reviews showed, the levels of the inflammatory marker C-reactive protein (CRP) dropped in participants following a plant-rich diet compared with those following a control diet by an average of 0.55 mg/l, and the levels of interleukin-6 dropped by 0.25 ng/l.

“Our results suggest that by following a plant-based diet, overweight people significantly improve their inflammatory marker profiles and thus can potentially contribute a lot to preventing common serious diseases such as heart attack and diabetes,” said study leader Aleksandrova. “By definition, a plant-based diet consists mainly of vegetables, grains, legumes and fruit. Moreover, it contains no or very little meat, but can include moderate amounts of eggs, dairy products and fish ,” added first author Eichelmann.

Why does being overweight or obese promote inflammation?
The body’s fat deposits not only store energy, they also secrete messenger substances. Since some of these substances promote inflammatory processes in the body, the inflammatory marker levels in the blood of overweight people are often elevated – a condition that in turn is associated with a significantly increased risk of metabolic diseases.
The number of morbidly obese people is steadily increasing, not only in Germany but also worldwide, and therefore researchers and physicians are looking for scientifically founded nutritional strategies that help people to stay healthy despite their excessive body weight.

Why a meta-analysis?
Observational and intervention studies** have indicated for a long time that a plant-based diet counteracts inflammatory responses related to excess weight. Often, however, the number of participants in the intervention studies is relatively small, so that the observed effects are sometimes only slight. “That is why we conducted an extensive, systematic literature analysis and conflated the individual results of the respective intervention studies for the first time into an overall result. This makes it possible to better evaluate how strong the effect of such a diet is on the development of chronic inflammation – an important prerequisite for making recommendations,” said Eichelmann.

Basis of the studies
In the current analysis, the researchers studied all relevant nutritional studies that were published from January 1946 to January 2016 in Medline, EMBASE and in the Cochrane Central Register of Controlled Trials. Of the originally identified 2,583 studies, only 29 publications with data of a total of 2,689 study participants between the ages of 28 and 68 years fulfilled the selection criteria for the meta-analysis. The inclusion criteria were as follows:

●    The study was an intervention study.
●    The study participants were older than 18 years.
●    The intervention diet consisted of plant-based foods, but small amounts of meat, fish, and dairy products were allowed.
●    There was a sufficiently large amount of data to capture differences in the inflammatory marker levels between the intervention group and the control group.

Background information
* In meta-analyses, the researchers conflate the individual results of several studies into one overall result in order to develop a single conclusion with regard to a question.

** In some intervention studies, the same participants are examined before and after an intervention (treatment), e.g. prior to a specific diet and afterwards. In other intervention studies the scientists investigate the study participants by means of a so-called cross-over design. The study participants – if possible randomly selected – are divided into two participant groups.
While one group receives the diet under investigation in the study (e.g. a plant-based diet), the second group receives a control diet. After half of the of the study period, the groups switch. The intervention group receives the control diet and vice versa.

Overweight/obesity: The number of overweight and obese adults has increased worldwide to more than 1.9 billion and continues to rise.
In Germany alone, more than half of the women and men are overweight, and according to the Robert Koch Institute, nearly one in four adults are obese. But not only in Europe and the U.S. are many people overweight, even countries in Africa are affected. With the increased incidence of overweight and obesity, the number of people suffering from chronic diseases such as type 2 diabetes has also risen. An estimated six million people in Germany have diabetes. It therefore appears quite essential to develop effective counter-strategies.