Traditional African diets have long been known as beneficial for gut and metabolic health, because they usually include a range of vegetables, grains, fruit, and fermented goods, but while the impacts of adopting a diet rich in heavily processed and high-calorie foods have been studied worldwide, African populations have been under-represented in the data.
“Previous research has focused on other traditional diets, like the Japanese or Mediterranean diet,” said infectious disease specialist Quirijn de Mast from Radboud University Medical Centre in The Netherlands.
“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. The continent’s rich diversity in traditional diets offers unique opportunities to gain valuable insights into how food influences health.”
A study led by De Mast investigated the health effects of switching between a Kilimanjaro heritage-style diet and one considered more Western among northern Tanzanians.
Science Alert reports that the changes were both rapid and profound, with notable impacts on immune and metabolic profiles detectable within weeks of replacing traditional food items of various porridges, okra, sour milk, and fermented grains, with a menu featuring sausages and white bread, jams, pancakes, tomato sauce and French fries or vice versa.
The team recruited 77 healthy men from urban and rural parts of Northern Tanzania, who either habitually ate Western foods or tended to stick to a more traditional fare such as “kiburu” – boiled green plantain with kidney beans – washed down with a bowl of fermented banana and millet called “mbege”.
After a week of their usual daily rotation of meals, a selection of volunteers were instructed to swop for two weeks. Some urban recruits were asked to instead enjoy a serving of low-alcohol mbege with their usual Western meal for one week, before reverting to their old habits.
At key points throughout the investigation the researchers took blood samples to analyse cell types, the production of immune signals called cytokines, and the production of numerous metabolic compounds.
Those who switched from Kilimanjaro cuisine to items like bread and sausages showed elevated levels of inflammatory proteins and markers of metabolic dysregulation, with a significant drop in immune response to a number of fungal and bacterial pathogens.
They also experienced slight weight gain, which can’t be ruled out as a potential contributing factor to other metabolic changes.
Conversely, moving from Western foods to more fruits, fermented foods, vegetables, and whole grains increased anti-inflammatory responses, giving the immune system a boost.
Even a week of drinking the traditional fermented beverage improved activation of critical defence cells called neutrophils, and boosted chemical responses to fungal pathogens like Candida.
Surprisingly, the influence of the diet swops were still detectable four weeks later, making it clear that health changes were not only swift but could also be long-lasting.
Not only are Western diets being adopted across the African continent, supplementing if not replacing meals based on healthier items, but emigrants from African cultures moving into Westernised communities face an even greater challenge retaining a heritage that might be healthier for them.
“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,” said De Mast.
This study was published in Nature Medicine.
Study details
Immune and metabolic effects of African heritage diets versus Western diets in men: a randomised controlled trial
Godfrey Temba, Tal Pecht, Vesla Kullaya et al.
Published in Nature Medicine on 3 April 2025
Abstract
African heritage diets are increasingly being replaced by Western-style dietary patterns because of urbanisation, economic development, increased access to processed foods, globalisation and changing social norms. The health consequences of this nutrition transition are not well understood. We conducted a randomised controlled trial in the Kilimanjaro region in Northern Tanzania to investigate the immune and metabolic effects of switching between Kilimanjaro heritage-style and Western-style diets for 2 weeks and consuming a traditional fermented banana beverage (‘Mbege’) for 1 week. Seventy-seven young and healthy volunteers assigned male at birth, some living in urban areas and some living in rural areas, were recruited in the trial. Primary outcomes were changes in the immune and metabolic profile before and after the intervention and at the four-week follow-up. The switch from heritage-style to Western-style diet affected different metabolic pathways associated with non-communicable diseases and promoted a pro-inflammatory state with impaired whole-blood cytokine responses to microbial stimulation. In contrast, the switch from Western-style to heritage-style diet or consuming the fermented beverage had a largely anti-inflammatory effect. Some of the observed changes in the immune and metabolic profiles persisted at the follow-up, suggesting a sustained impact from the short-term intervention. These findings show the metabolic and immune effects of dietary transitions and the consumption of fermented beverages, underscoring the importance of preserving indigenous dietary practices to mitigate non-communicable disease risk factors in sub-Saharan Africa.
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