Just Two Weeks on a Western Diet Triggers Inflammation and Weakens Immunity, Study Finds
A dramatic shift in diet—even for just two weeks—can significantly impact the immune system, inflammation levels, and overall metabolic health, according to a new study published in Nature Medicine. Researchers found that switching from a traditional African diet to a Western diet sparked inflammation, reduced the body’s immune response to infections, and activated biological processes linked to chronic diseases. In contrast, returning to a fiber-rich, vegetable-heavy African diet or consuming fermented foods showed immediate and lasting health benefits.
With lifestyle diseases such as heart disease, diabetes, and chronic inflammation on the rise across Africa, the study sheds light on the dietary habits driving these trends. Economic growth, urbanization, and increased availability of processed foods are accelerating the adoption of Western eating patterns, prompting urgent questions about their health impact.
To investigate, scientists from Radboud University Medical Center in the Netherlands and KCMC University in Tanzania examined 77 healthy Tanzanian men from both urban and rural areas. The participants were divided into four groups: some shifted from a traditional African diet to a Western one, others did the reverse, a third group consumed a daily fermented banana drink, and a control group maintained their regular diet. The researchers tracked immune system activity, inflammation markers, and metabolic responses at baseline, after two weeks, and again four weeks later.
Those who adopted a Western diet quickly showed elevated levels of inflammatory proteins in their blood and a weakened immune response to pathogens. Additionally, biological pathways tied to lifestyle diseases were activated. In contrast, participants who embraced the traditional African diet or drank the fermented banana beverage experienced reduced inflammation—some of which lasted even a month after the diet change.
This is the first study to thoroughly map the health benefits of a traditional African diet, which typically includes vegetables, legumes, whole grains, fruits, and fermented foods. “While much attention has gone to the Mediterranean and Japanese diets, Africa’s traditional diets also offer powerful insights,” said Dr. Quirijn de Mast, internist at Radboudumc. “These findings are especially important now as dietary habits are rapidly changing across the continent.”
Dr. de Mast emphasized the surprising speed and significance of the changes: “Just two weeks of dietary adjustment had a noticeable impact on inflammation and immune health. It’s a strong reminder of how quickly our bodies respond to what we eat.”
The study also carries a warning for Western nations, where diets high in processed foods, salt, sugar, and saturated fat are common. Chronic inflammation is a root cause of many modern diseases, making the findings globally relevant.
The research was a collaboration between Radboudumc, KCMC University, and international partners from Bonn and Florence, with funding provided by ZonMw/JPI-HDHL.
