A new study published in Nature Medicine shows that switching from a traditional African diet to a Western-style diet for just two weeks can weaken the immune system and trigger inflammation. The research highlights how quickly food choices can affect our health—and how traditional diets may protect against chronic diseases.
The study was led by scientists from Radboud University Medical Center in the Netherlands and KCMC University in Tanzania. It focused on the rising rates of lifestyle-related diseases like heart disease, diabetes, and chronic inflammation in Africa.
These diseases are becoming more common as processed, high-fat, and sugary foods—typical of Western diets—become more available due to urbanization and economic growth.
To explore how diet impacts the body, researchers studied 77 healthy men living in both urban and rural areas of Tanzania. Participants were divided into different groups. Some who usually ate a traditional African diet switched to a Western diet for two weeks.
Others who normally ate a Western-style diet tried a traditional African diet instead. A third group stayed on their usual diet but drank a fermented banana drink every day. A control group continued with their regular eating habits.
Before, during, and after the two-week period, researchers carefully measured immune system activity, levels of inflammation in the blood, and changes in metabolism. They also checked again four weeks after the diet experiment ended to see if the effects lasted.
The results were striking. People who switched to a Western diet showed higher levels of inflammatory proteins in their blood. Their immune cells also responded less effectively when exposed to germs, meaning their ability to fight infections had weakened. Additionally, processes in the body linked to lifestyle diseases were activated.
In contrast, those who switched to a traditional African diet—or drank the fermented banana drink—showed lower levels of inflammation. These benefits were still seen even four weeks after the diet change ended, suggesting that healthy food choices can lead to lasting improvements in health.
This study is the first of its kind to examine the traditional African diet in such detail. According to Dr. Quirijn de Mast, a physician involved in the research, there’s a lot we can learn from African diets. While diets like the Mediterranean or Japanese diets have been studied for years, African eating patterns also offer important insights into how food affects the body.
Traditional African diets often include vegetables, fruits, beans, whole grains, and naturally fermented foods. These foods are high in fiber and nutrients and are low in harmful fats, salt, and added sugar.
In contrast, Western diets tend to rely heavily on processed items such as white bread, French fries, and sugary snacks. These foods can increase inflammation and lead to long-term health problems.
“Inflammation is at the root of many chronic diseases,” Dr. de Mast explained. “What’s remarkable is that these harmful effects can start after just two weeks on an unhealthy diet.”
This study sends a powerful message: what we eat can change how our body works in a matter of days. And while switching to an unhealthy diet can damage the immune system, even a short return to traditional, plant-based foods can have real benefits.
The study offers clear evidence that diet has a fast and strong impact on the immune system and metabolic health. While it focused on Tanzanian men, the findings have global relevance, especially for countries facing a rise in lifestyle-related illnesses.
One key takeaway is how sensitive the body is to changes in diet—even short-term ones. The increase in inflammation and drop in immune strength after just two weeks of eating Western-style foods is concerning, especially for people already at risk for chronic conditions.
It also shows how important it is to maintain a diet rich in vegetables, fiber, and fermented foods, which support gut health and reduce inflammation.
This research could guide public health strategies, especially in developing countries where dietary habits are shifting quickly. It also adds to the growing body of science showing that traditional, whole-food diets can help prevent serious diseases.
In summary, this study reminds us that food is not just fuel—it’s medicine. Making smart food choices, even for a short time, can lead to better health and stronger immunity.
If you care about health, please read studies that vitamin D can help reduce inflammation, and vitamin K could lower your heart disease risk by a third.
For more health information, please see recent studies about new way to halt excessive inflammation, and results showing foods that could cause inflammation.
The research findings can be found in Nature Medicine.
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