26 May 2025

I’ve written extensively about the simmering epistemic crisis – a crisis in which there is no agreed-upon reality – that reached boiling point during the manufactured COVID crisis, dramatically transforming the process by which people gather information about their world, and make decisions about who and what to believe. In my corner of that world – health science – the epistemic crisis spawned the proliferation of self-appointed ‘influencers’ who trade on the trope that everything the experts tell you about nutrition is wrong, but I have the truth that’s been hidden from you.

Looking back through my archive, I’ve spilled reams of digital ink on systematically and meticulously debunking the giant steaming piles of bulldust deposited by these carnival barkers, from ‘lectins cause every disease from arthritis to obesity by damaging your gut lining’ (they don’t), to ‘phytates are antinutrients that rob your body of vital minerals’ (they aren’t), to ‘carbs make you fat and you should eat more fat to lose weight’ (they don’t, and you shouldn’t) to ‘seed oils cause heart disease while animal fats are good for heart health’ (they don’t, and they aren’t), ‘your blood type determines what kind of diet you should eat’ (it doesn’t), to ‘cancer, without exception, is fuelled by glucose’ (it isn’t), to ‘eating cholesterol is necessary for brain health, and low cholesterol causes dementia, cancer and premature death’ (it isn’t, and it doesn’t), to ‘eating meat made us human, so you should lots of it if you want to maximise your health and longevity’ (it didn’t, and you shouldn’t).

Gawd, this whole bulldust-busting business gets bloody tiresome, especially when the vast majority of people seem to want to be taken in by simplistic arguments purveyed by overconfident hucksters… and to be utterly unwilling to read or listen to thorough analysis that acknowledges the uncertainty inherent to the scientific process.

But every now and again, a study comes out that demolishes all the silly nonsense spouted by social media nutrition ‘experts’, with exquisite simplicity. And just such a study was recently published in Nature Medicine. Titled ‘Immune and metabolic effects of African heritage diets versus Western diets in men: a randomized controlled trial‘, the study investigated the impact of switching the customary diets of rural and urban Tanzanians for just two weeks, on a diverse array of immune and metabolic markers and blood proteins, and on gene expression.

The researchers were focused on biomarkers related to chronic illnesses that are still comparatively rare in Tanzania but are rapidly accelerating, especially in city-dwellers – illnesses such as diabetes, cardiovascular disease and chronic inflammatory conditions. Whereas urban-dwellers in Western countries like Australia enjoy better health and longer lives than their rural and remote counterparts, the reverse is true in sub-Saharan Africa, where urban adults have higher mortality than rural adults.

What might explain this urban-rural mortality flip between developed and developing countries? One possibility is that in developed countries, just about everyone eats Calorie-Rich And Processed food – that’s CRAP, for short¹ – but in developing countries, rural people are still largely eating their traditional diets, while urban people have greater exposure to CRAP.

Previous research by the same team of researchers had identified higher levels of inflammatory markers in the blood of urban Tanzanians, who have much greater access to Western-style foods than their rural compatriots. They found that the lower inflammation in rural people was associated with higher blood levels of metabolites from phytonutrients (plant-derived nutrients) including flavonoids and complex sugars. Conversely, the higher burden of inflammatory markers in urban people was associated with more abundant metabolites of bile acids and cholesterol, which are markers of higher intake of fat and animal products.

If you’re finding this a bit hard to follow, I’ll boil it all down for you: more plant foods = less inflammation; more fat and animal foods = more inflammation.

But that previous study was observational, and observational studies have a major limitation: there can be confounding factors that obscure the true relationships between the variables that scientists observe. For example, maybe the reason that urban-dwelling Tanzanians have higher inflammatory markers is because they’re exposed to more air pollution, or more psychosocial stress than their rural cousins, rather than because they eat different diets. To be certain that Western-style diets increase inflammation, you need an intervention study, in which the researchers intentionally change the dietary patterns of participants.

And that’s exactly what the researchers did. They recruited 28 young rural-dwelling men who habitually consumed their traditional diet, described as “a Kilimanjaro heritage-style diet”, and 27 young urban-dwelling men whose diet was far more Westernised, and had all but five of the men in each group swap diets for two weeks. (Those additional five men in each group who maintained their customary diets served as controls, to assess diet-independent effects on biomarkers.)

The Kilimanjaro heritage-style diet was centred on starchy foods including Ugali (a stiff porridge made from maize flour, cassava, or sorghum), boiled plantain (green banana), cooked maize and rice, along with legumes, fresh fruit and vegetables (especially leafy greens). Meat intake was low.

The urban diet featured meat (beef, pork, chicken, fish, organ meats) at most meals, along with white bread, and packaged fruit juice; Ugali was also consumed fairly regularly, but other starchy foods like plantain, cassava and potato were fried in oil rather than boiled as in the rural diet. Vegetable intake was low in urban-dwellers.

So for the experiment, the rural men ate the urban diet for two weeks, while the urban men ate the rural diet. The research team provided three freshly-prepared meals per day to all participants, according to the following plan:

The approximate macronutrient composition of the diets, expressed as percentage of energy derived from each, was as follows:

Kilimanjaro heritage-style diet:

• 81% carbohydrate
  • 60% complex carbohydrates in the form of unrefined starchy foods
  • 7% simple sugars
  • 14% dietary fibre
• 11% protein
• 7% fat

Western-style diet:

• 60.7% carbohydrate
  • 55% starches (primarily refined)
  • 2.2% simple sugars
  • 3.5% dietary fibre
• 16% protein
• 23% fat

In an additional arm of the study, 22 young urban men continued on their habitual Westernised diet, but received one litre per day of a traditional fermented drink called Mbege, for one week. Mbege is made by fermenting boiled banana and germinated finger millet, to produce a beer-like beverage with 1-3 per cent alcohol content ².

Blood samples and biometric data were collected from all participants at baseline, at the end of the intervention (two weeks for the diet arm, and one week for the Mbege arm), and then again at four weeks after the intervention had finished.

So what happened? Here’s the TL;DR³: Switching to the Western-style diet jacked up inflammation levels and impaired immune responses in the rural men, with some inflammation markers remaining persistently high even after the men had been back on their traditional diets for four weeks, and vice versa: the traditional diet and the fermented banana beverage persistently decreased inflammation.

In more detail, in the rural men who were switched to the Western diet:

• All men gained weight; median weight gain was 2.6 kg in just two weeks of eating more animal foods, refined carbohydrates and oils. Meals were served ad libitum – that is, the men were instructed to eat as much as they needed to satisfy appetite – and the men ended up eating more calories on the Western diet than on their high-fibre, unrefined starch-rich traditional diet.
• Levels of multiple proteins and other markers associated with inflammation and cardiometabolic disease increased, including one of the most widely-used markers of inflammation, plasma C-reactive protein (CRP). Among the most affected were proteins involved in atherogenesis (plaque formation). Fortunately, most (but not all) of these markers returned to baseline levels after the men went back to eating their traditional diets for four weeks.
• Metabolites associated with glucose homeostasis and the urea cycle increased, indicating greater stress on the men’s ability to regulate their blood sugar level and to metabolise the higher intake of animal protein.
• The long chain omega-3 fatty acid eicosapentaenoic acid (EPA) significantly decreased, while docosahexaenoic acid (DHA) showed a trend toward decreasing.
• Levels of dopamine, a neurotransmitter associated with reward and motivation, transiently declined.
• When exposed to a number of common pathogens including Candida albicans and Staphylococcus aureus, the white blood cells of the rural men switched to the Western diet showed a more inflammatory but less effective immune response, which, as the authors noted, “is consistent with reduced cytokine production commonly observed in inflammatory conditions such as aging¹⁷, obesity¹⁸, endotoxemia¹⁹ or sepsis²⁰“. In other words, two weeks on a high fat, refined carbohydrate- and meat-heavy diet caused these young men to have the inefficient but highly inflammatory response to infection that we see in old, fat and very sick people.
• Genes associated with response to reactive oxygen species (‘free radicals’) and innate immune system responses to bacteria were upregulated, indicating that the men’s bodies were under increased oxidative stress and (most likely) bacterial metabolites ‘leaking’ from their guts due to increased fat and decreased fibre intake.
• Total white blood cell count, and counts of subtypes of white blood cells including neutrophils, immature granulocytes and monocytes were all increased. This pattern of immune activation is a hallmark of inflammation.

In the urban men switched to the Kilimanjaro heritage diet:

• Levels of multiple inflammatory markers and proteins involved in cardiometabolic disease declined, and some of these remained lower than baseline even after the men had returned to their customary diets for four weeks, indicating a lasting benefit of their brief period on the traditional high-fibre, high-unrefined starch, vegetable-rich and relatively low animal protein diet.
• Dodecanoic acid (lauric acid), a fatty acid which enhances mitochondrial function and glucose and lipid metabolism, increased.
• The omega-3 polyunsaturated fatty acids DHA, docosapentaenoic acid (DPA) and EPA all increased.

In the urban men who added the fermented banana beverage, Mbege, to their standard, Westernised diet:

• Consumption of the fermented beverage for just one week caused persistent reductions in some inflammatory markers, and tamped down the inflammatory response of white blood cells to pathogens.
• Certain metabolites formed by gut microbial breakdown of dietary polyphenols, and which are associated with vascular health and anti-inflammatory effects, were increased.
• Genes involved in damping down inflammatory activity were upregulated.
• Neutrophil reactivity was reduced, indicating a less inflammatory immune profile.

Summing up, switching young healthy rural Tanzanian men to a Western dietary pattern heavy in animal protein, saturated fat, dietary cholesterol, salt and refined carbohydrate for just two weeks, induced a pro-inflammatory state and dialled up key metabolic pathways linked to cardiometabolic and inflammatory diseases – and some of these disease-promoting changes persisted even four weeks after the men returned to their customary traditional diets.

Conversely, switching urban men to a largely plant-based heritage diet rich in green vegetables, legumes, plantains, root and tuber crops such as cassava and taro, and whole grains (millet, sorghum) for two weeks, or adding a fermented beverage made from banana and millet to their customary Westernised diet for one week, induced anti-inflammatory effects, some of which also persisted to the four-week follow-up point.

In case you missed it, I’ll underline a very important point: the Kilimanjaro heritage diet used in this study is extremely high in carbohydrates, phytochemicals, lectins and fibre – constituents that (inexplicably) popular nutrition influencers like Paul Saladino, Robert Kiltz, Paul Mason, Anthony Chaffee and Steven Gundry urge their gullible disciples to shun, based on the completely evidence-free claim they are pro-inflammatory, and promote obesity, diabetes, heart disease and cancer. Yeah, right.

The take-home messages from this study are:

1. Not only is the Western diet unhealthy; it puts even healthy young people on the road to cardiometabolic and chronic inflammatory diseases within a shockingly brief period of time.
2. Diets based on carbohydrate-rich, minimally-processed plant foods rapidly reduce inflammation and tamp down pathways involved in cardiometabolic diseases, and these beneficial effects are quite persistent. So it’s never too late, and you’re never too far gone, to benefit from improving your diet!
3. Fermented foods have beneficial effects on inflammation and immune system activity.
4. If you’re still paying any attention to the blatherings of numbskulls who tell you that diets centred on minimally-processed plant foods are bad for you, you might be beyond help (OK, strictly speaking that was my extrapolation from the study, but I reckon it’s reasonable).

Have you sampled any of these traditional African foods, including Mbege? Or have you improved your health by returning to the wholesome dietary practices of your ancestors? Leave a comment below!

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1. In my personal experience, rural people’s eating habits are generally worse than city-dwellers’, if my observations of what goes into people’s shopping trolley are any guide. ↩︎
2. I’m continually struck by the ingenuity of humans, who will turn just about anything available to them into alcohol 😆. ↩︎
3. Too long; didn’t read. ↩︎