Two Weeks on Western Diet Triggers Immune Dysfunction | Image Source: www.medicalnewstoday.com
MOSHI, Tanzania, 8 April 2025 – In a surprising new study published in Nature Medicine, researchers found that a two-week dietary change – from a traditional African diet to a Western diet - can significantly disrupt the body’s immune and metabolic systems. This randomized trial in the Kilimanjaro region of Tanzania, involving 77 healthy youth, provides some of the clearest evidence to date that food options directly influence inflammation, immunity and long-term health.
The collaborative study conducted by the Radboud University Medical Centre in the Netherlands and the Kilimanjaro Christian Medical University College (KCMC) in Tanzania sought to explore how traditional diets, rooted in plant foods, rich in fibre and little processed, are compared to modern Western diets rich in sugars, refined carbohydrates and saturated fats. The conclusions are both clear and disturbing, especially as urbanization and globalization continue to influence food habits in Africa and beyond.
What was the purpose of the study?
According to Chief Investigator Dr. The study was designed to measure how different diets affect the main immune and metabolic markers. Participants were divided into three groups: those that moved from a traditional African to a traditional Western regime, those that moved from WD to a special regime, and a third group that continued their diet but added a traditional fermented banana beverage called Mbege. Ten participants served as witnesses by maintaining their usual eating habits throughout the study.
“We wanted to see not only how these diets affect general health, but how they modulate the immune system at the cellular and molecular level,” says Mast. To this end, the researchers collected blood samples at three key points: before the procedure, immediately after, and four weeks later. The data were analyzed multi-omical, including metabolomics, proteomics, and transcriptomics, providing a complete map of the body’s response.
How does a Western diet affect the immune system?
In just 14 days, participants who moved from an African heritage diet to a Western diet showed a significant increase in inflammation-related proteins in their bloodstream. These included high levels of reactive proteins C (CRP), inflammatory cytokines such as IL-6 and TNF, and indicative white blood cell activity in systemic inflammation. In addition, their immune cells showed a reduced ability to fight pathogens, indicating that their natural defences had weakened.
The Western diet group has also shown active biological pathways associated with chronic diseases such as cardiovascular disorders, type 2 diabetes and metabolic syndrome. “We were surprised by the speed and intensity of these effects,” said Mast. “Even in young men, otherwise healthy, the immune system reacts quickly – and not in a good way – to a diet rich in processed foods, sugar and saturated fats. “
What are the benefits of feeding African heritage?
On the contrary, participants who adopted the traditional diet of the Kilimanjaro region, rich in whole grains, legumes, green vegetables, roots and fermented products, saw markers of inflammation decrease and improve immune function. The anti-inflammatory response was not only rapid, but also showed signs of persistence, as the beneficial markers remained weak even four weeks after returning to their usual diet.
As indicated in the Medical News Today, this plant-based food style provides the body with high levels of dietary fibre, polyphenols and essential micronutrients. These components feed the intestinal microbe, promote the growth of beneficial bacteria and stimulate the production of short chain fatty acids – compounds that regulate immune responses and reduce chronic inflammation. Fermented banana drink, Mbege, also contributed to these benefits by enriching the intestinal microbe with live crops and bioactive metabolites.
Why is this study important now?
Throughout Africa, the prevalence of lifestyle-related diseases – diabetes, obesity, cardiovascular problems – is increasing. Urbanization and the availability of low-cost processed foods have resulted in a steady decline in traditional eating habits. According to the researchers, this study could not arrive at a more critical moment. “There is an urgent need to protect and promote indigenous food traditions before they disappear under the influence of globalization,” said Thomas M. Holland, a medical scientist at the RUSH Institute for Healthy Aging, who did not participate in the study.
The Netherlands explained that the marked contrast between group immune profiles was largely due to nutritional composition and microbial exposure. Western diets lack microbial diversity and plant nutrients to support a balanced immune system. On the other hand, heritage regimes naturally cultivate this balance.
How was the study conducted?
Participants were selected on the basis of strict inclusion criteria, such as membership in self-covered diet, the range of BMI from 18 to 25 years old, and residence in rural or urban Kilimanjaro at least one month prior to the study. Its food intake was assessed using 24-hour food recovery reviews and confirmed by local nutritionists. Meals during the intervention period were prepared and consumed under supervision to ensure compliance and consistency.
Researchers used a variety of sophisticated tools to analyze biological responses, including blood tests, gene expression profiles, cytokine quantification, and proteomics mapping. Statistical models adjusted for factors such as age, BMI and level of physical activity. Importantly, the study followed the ethical guidelines established by Tanzanian health authorities and international research standards, and all participants gave their informed consent.
What does this mean for public health?
Although research has been carried out in a specific African region, its consequences go far beyond Tanzania. The results draw the attention of policy makers, nutritionists and health care providers around the world. A simple two-week dietary change can significantly alter immune function, with potentially lasting effects. This raises critical questions: What happens when this food change lasts years? What does this mean for children raised in a Western diet from birth?
As the Medical Xpress has reported, inflammation is a common root of many modern diseases. By demonstrating that food changes can quickly influence inflammation and immunity, this study establishes a compelling argument for urgent food reform, not only in Africa, but in any region where Western eating habits are changing traditional food routes. “It’s not about romance,” said Mast. It is a question of recognizing the wisdom rooted in traditional food cultures and using it to inform modern food recommendations
Are there enough food changes in the short term to see the results?
At least in part. One of the most surprising results of the study was the discovery that some of the immune and metabolic changes persisted four weeks after the intervention. This suggests that even short-term changes in diet can have persistent benefits or consequences, depending on the direction of change.
For example, participants who consumed the fermented drink for one week showed a reduction in inflammation markers that lasted well beyond the intervention period. This indicates the resilience of the microbe and its potential for rapid recovery - or degradation – depending on food intake.
“It is encouraging to see that improvements are possible, and quickly,” added the Netherlands. “The body reacts remarkably well to real and complete foods. Of course, the flip side is that it also deteriorates so quickly when it is bombarded with ultra-treated garbage. “
What is the continuation of this investigation?
The team is already planning follow-up studies, in particular on the long-term effects of food transitions and their impact on chronic disease prevention. Another key area of interest is the intestinal microbiome, which was only partially addressed in this study. Full results on microbial composition are expected in future publications, as noted by the research team.
“This is only the beginning,” said Mast. “We hope to explore how different traditional food combinations, not only in Africa, but globally, can support immune health. It’s time to look beyond pills and procedures and recognize food as one of our most powerful tools in preventive medicine. “
At a time when fast food has become a predetermined option, this research reminds us of a simple and neglected truth: what we eat today forms what we feel tomorrow and how long we will be healthy in the long term.
