Switching to a Western diet triggers inflammation and weakens immunity

A switch of just two weeks from a traditional African diet to a Western diet causes inflammation, reduces the immune response to pathogens, and activates processes associated with lifestyle diseases. Conversely, an African diet rich in vegetables, fiber, and fermented foods has positive effects. This study, published in Nature Medicine, highlights the significant impact of diet on the immune system and metabolism.

Lifestyle diseases such as cardiovascular diseases, diabetes, and chronic inflammatory conditions are surging across Africa, posing a growing challenge to healthcare systems throughout the continent. Increasing economic development, urbanization and wider availability of processed foods have accelerated the adoption of Western eating habits in Africa. To understand the health consequences of this shift, researchers from Radboud university medical center and KCMC University in Tanzania have studied the effects of such dietary changes on health.

Lifestyle diseases

Seventy-seven healthy men from Tanzania, both urban and rural residents, participated in the study. Some participants who traditionally ate an African diet switched to a Western diet for two weeks, while others who ate a Western diet adopted a traditional African diet. A third group consumed a fermented banana drink daily. As a control, ten participants maintained their usual diet. The researchers comprehensively analyzed the function of the immune system, blood inflammation markers, and metabolic processes at baseline, after the two-week intervention, and again four weeks later.

Participants who switched to a Western diet exhibited an increase in inflammatory proteins in their blood, alongside activation of biological processes linked to lifestyle diseases. Their immune cells also responded less effectively to pathogens. Meanwhile, those who switched to a traditional African diet or consumed the fermented drink showed a reduction in inflammatory markers. Some of these effects persisted even four weeks later, indicating that short-term dietary changes can have long-lasting effects.

Insights from Africa

This is the first study to comprehensively map the health effects of a traditional African diet. 'Previous research has focused on other traditional diets, such as the Japanese or Mediterranean diet', says internist Quirijn de Mast from Radboudumc. 'However, there is just as much to learn from traditional African diets, especially now, as lifestyles in many African regions are rapidly changing and lifestyle diseases are increasing. Africa's rich diversity in traditional diets offers unique opportunities to gain valuable insights into how food influences health.'

De Mast finds it remarkable how significant the effects of diet are, even after just two weeks. 'The African diet includes plenty of vegetables, fruits, beans, whole grains, and fermented foods. Our study highlights the benefits of these traditional food products for inflammation and metabolic processes in the body. At the same time, we show how harmful an unhealthy Western diet can be. It typically consists of processed and high-calorie foods, such as French fries and white bread, with excessive salt, refined sugars, and saturated fats. Inflammation is at the root of many chronic conditions, which makes this study highly relevant for Western countries as well.'

Radboudumc and KCMC University collaborated on this study with international partners from Bonn and Florence. The research was funded by ZonMw/JPI-HDHL.