Chapter 3

Sugar in Traditional Diets

Contemplate traditional diets as human evolutionary adaptation to the available food in their local environments. Those who ate the local good food survived.”

In September, 1835, a 22-year-old Charles Darwin—recently graduated from Cambridge University and assigned as the naturalist aboard HMS Beagle—stood upon the volcanic shores of the Galápagos Islands. Over the next five weeks, he observed what would become a quiet revolution in biological thought. The finches, varying subtly in beak shape and size from one island to the next, revealed a deeper story of adaptation—of traits shaped by environmental need. It was here that Darwin first glimpsed the principle of natural selection: that survival rests not upon strength alone, but upon one’s ability to adapt.

In much the same way, human diets evolved as regional expressions of environmental adaptation. As our ancestors spread across the globe over tens of thousands of years, they encountered vastly different ecosystems—arid deserts, frozen tundra, fertile plains, tropical forests—and, crucially, they learned to eat what those environments offered. The foods available were not chosen randomly but were refined through generations of practice and survival. Only those who adapted to the local food supply—its preparation, seasonality, and nutritional content—would thrive.

These traditional diets were deeply rooted in land, climate, and culture. They were shaped by centuries of observation, experience, and necessity. Regardless of macronutrient composition—whether dominated by plant starches, animal fats, or seasonal fruits—these diets matched the metabolic and genetic profile of the people who consumed them. From the coconut-rich diets of Polynesia to the fat-heavy sustenance of the Arctic, traditional eating patterns represent not random habits, but refined biological alignment.

If the environment—and the available food—changed slowly, the human population had time to adapt. Over centuries, genetic variants would emerge to suit the new conditions. But when food systems changed suddenly, whether from natural disaster or colonization, adaptation could not keep pace. Some communities migrated. Others starved. Those who survived often bore genetic traits—now called “starvation genes”—that helped store energy more efficiently.
This chapter offers a global tour of traditional diets. The cultures described here are not exhaustive, but they are representative of populations that lived in relative isolation until the past two centuries. With the arrival of industrialized food—especially sugar and refined carbohydrates—these ancestral dietary frameworks began to collapse. The consequences, as we shall see, are visible in our genetic mismatches, disease patterns, and biochemical fragilities.


 3.2: The Arctic: A Carnivorous Diet from the Sea

In the harsh expanse of the Arctic, where icy winds sweep over a barren landscape and the soil yields little to no vegetation, the Inuit people forged one of the most remarkable dietary systems in human history. Deprived of grains, fruits, or plant oils, the Inuit adapted to a diet drawn almost entirely from the sea. It was a diet of precision and resilience, built on generations of inherited knowledge and biological hardening.

Marine mammals such as seals and whales formed the dietary core. Their fat—rich in energy-dense triglycerides and omega-3 fatty acids—provided the calories necessary to survive sub-zero conditions. The meat and organs of these animals delivered protein, vitamin D, iron, and other vital micronutrients, while fermented fish ensured a reliable food source during the long, dark winters. Arctic char and salmon added seasonal variety, and every part of the animal was used. Bones became tools, intestines became rope, and nothing was wasted.

This way of eating was not only cultural—it was genetic. Modern genomic studies show that the Inuit possess unique adaptations that allow them to metabolize large quantities of marine fat efficiently. One such adaptation involves enhanced processing of long-chain omega-3 fatty acids, reducing inflammation and protecting cardiovascular health. Additionally, the Inuit display variants in genes regulating fat metabolism, enabling them to thrive on diets high in animal fat without the deleterious effects seen in other populations exposed to similar macronutrient profiles.

Interestingly, the Inuit do not appear to carry high frequencies of classical “starvation genes” such as SLC2A9, PNPLA3, or ABCG2. Their adaptations are distinct—designed not for feast and famine, but for chronic cold and nutritional scarcity from plant-derived foods. However, their resilience did not prepare them for the one ingredient they had never encountered: fructose.
In 1951, German physician Dr. Otto Schaefer undertook a landmark study of the Inuit of Baffin Island in Canada. His findings were striking. Where Inuit communities ate traditional diets of raw, frozen meat and marine fat, they exhibited no signs of diabetes, obesity, or cardiovascular disease. Yet in those same regions, when individuals began purchasing foods from Hudson’s Bay Company stores—especially flour, sugar, and canned goods—the pattern reversed. The sudden replacement of fats with carbohydrates triggered the onset of obesity, type 2 diabetes, and atherosclerosis.

Schaefer’s conclusion was simple but profound: the Inuit body was metabolically suited to fat, not sugar. The arrival of refined carbohydrates and fructose introduced a mismatch that their biology could not overcome. Within one generation, traditional food systems were eclipsed, and the diseases of modernity took hold.


3.6: Sub-Saharan Africa: Grains of Resilience

In the vast and varied landscapes of Sub-Saharan Africa, human diets evolved not only as a reflection of local resources but also as a response to extreme climatic challenges. From the arid Sahel to the humid equatorial forests, communities developed food systems rooted in sustainability, seasonality, and survival.

At the heart of many traditional African diets are millet and sorghum—resilient grains that thrive in hot, dry conditions. These grains were often ground into flour, fermented into porridge or beer, or baked into flatbreads. Unlike modern wheat products, these traditional preparations were rich in fibre, micronutrients, and slowly absorbed carbohydrates.

Root crops such as cassava, sweet potatoes, and yams added caloric density and seasonal variety. Leafy greens like moringa, amaranth, and cassava leaves contributed essential vitamins, minerals, and phytochemicals. Wild fruits, such as baobab pods, tamarind, and marula, provided bursts of vitamin C and polyphenols, while fermentation—widely practiced across the continent—enhanced nutrient bioavailability and preserved food through lean seasons.

In drier regions, pastoralism and hunting offered additional protein. Goats, cattle, guinea fowl, and bush meat enriched diets, often consumed sparingly but with cultural reverence. This combination of grains, tubers, wild greens, and modest animal protein formed a balanced and adaptive food system—low in sugar, high in fibre, and rich in antioxidants.

Among the most revealing case studies of African dietary adaptation are the Hadza of northern Tanzania. Living near Lake Eyasi on the edge of the Serengeti, the Hadza are among the last true hunter-gatherers on Earth. Only a few hundred individuals still follow a fully nomadic lifestyle, relying on foraging and hunting techniques refined over millennia.

Hadza men hunt with handmade bows, sometimes tipped with poison, targeting small antelope, birds, and monkeys. They also follow honeyguide birds, which lead them to hidden beehives. Honey, remarkably, accounts for nearly 20 percent of their caloric intake. Women gather baobab fruit, wild tubers, berries, and bird eggs, ensuring dietary diversity and seasonal resilience.

Despite consuming unrefined carbohydrates from honey and tubers, the Hadza exhibit very low rates of obesity, diabetes, and cardiovascular disease. Their diet is high in fibre and free of processed foods. Their gut microbiota, shaped by lifelong exposure to wild foods and soil microbes, shows extraordinary diversity—linked in emerging science to lower inflammation and improved metabolic health.

Culturally, the Hadza are fiercely egalitarian. There are no formal leaders, and food is shared communally. A successful hunt feeds the entire camp. Their shelters—grass domes or lean-tos—are temporary, reflecting seasonal migration in search of food and water.

Yet like many Indigenous peoples, the Hadza face existential threats. Over 90 percent of their ancestral land has been lost to tourism, agriculture, and resettlement schemes. Their unique click-based language, Hadzane, is endangered, and younger generations are increasingly drawn to urban life, education, and market economies.

One of the most important recent insights into African traditional diets came from a 2025 randomized controlled trial conducted in the Kilimanjaro region of northern Tanzania. Researchers compared the immune and metabolic effects of a heritage-style diet versus a modern urban-style diet, including a third intervention arm that consumed a traditional fermented banana beverage known as Mbege.

It was “a randomized 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 4-week follow-up. The switch from heritage-style to Western-style diet affected different metabolic pathways associated with noncommunicable 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 noncommunicable disease risk factors in sub-Saharan Africa.

“The heritage diet in this study is rich in green vegetables, legumes, plantains, root and tuber crops, including cassava and taro, and whole grains (millet, sorghum), providing dietary fiber and bioactive compounds like polyphenols, known for their anti-inflammatory properties and beneficial metabolic effects. Additionally, this diet promotes a favorable gut microbiome composition and production of beneficial metabolites. Our plasma proteomics and metabolomics analyses revealed changes in several classes of immuno-modulating compounds and metabolic pathways, including microbiota-derived metabolites....

"The immuno-metabolic benefits of this diet probably stem from synergistic interactions among diverse foods and bioactive compounds, rather than any single component, a pattern also seen with the Mediterranean diet.
“This study highlights the immuno-metabolic consequences of dietary transitions and suggests their potential effects beyond a short dietary intervention.”

The findings were profound. Volunteers who switched to the heritage-style diet experienced anti-inflammatory effects and improvements in metabolic markers, including cytokine response and lipid metabolism. In contrast, those who adopted a Western-style diet showed pro-inflammatory responses, altered immune signaling, and disruption of beneficial metabolic pathways. Some of these changes persisted even after the intervention ended, highlighting the lasting impact of even short-term dietary shifts.

The heritage diet studied was rich in green vegetables, legumes, plantains, root crops like cassava and taro, and whole grains such as millet and sorghum. It was high in dietary fibre, polyphenols, and fermentable substrates that supported a healthy gut microbiome.
Temba, G.S., Pecht, T., Kullaya, V.I. et al. Immune and metabolic effects of African heritage diets versus Western diets in men: a randomized controlled trial. Nat Med 31, 1698–1711 (2025). https://doi.org/10.1038/s41591-025-03602-0. CC license 4.0 Width adjusted to fit this book omits an image of local beer

According to the authors, the benefits stemmed not from any one component, but from the synergistic effects of whole, unrefined foods—a pattern echoed in the Mediterranean diet and other traditional systems around the world.

The findings of Godfrey Temba and his colleagues support what ancestral wisdom long knew: that traditional African diets were deeply protective, metabolically stabilizing, and immunologically beneficial. Their erosion under pressure from globalized food systems poses a direct threat not only to cultural heritage, but to public health.


3.7: The Pacific Islands: A Tropical Cornucopia

Scattered across the vastness of the Pacific Ocean lie thousands of islands—each shaped by volcanic soil, tropical climate, and marine abundance. For centuries, their inhabitants cultivated a symbiotic relationship with land and sea, resulting in traditional diets that were diverse, balanced, and astonishingly resilient.

Taro, breadfruit, and yams formed the carbohydrate foundation of many island diets. Taro, with its starchy corms and leafy greens, has been cultivated for over 2,000 years and consumed boiled, mashed into poi, or fermented. Breadfruit, a tree crop producing large, fibrous fruits, could be roasted, baked, or turned into flour and stored for months. Yams and sweet potatoes added seasonal variety and supported energy needs in physically active societies.

Coconut palms were central to island life. Coconut water provided hydration. Coconut flesh supplied healthy saturated fats. Coconut oil was used in cooking and medicine. The coconut’s contribution to food, ceremony, and ecology made it both a crop and a cultural symbol.
Seafood was essential—reef fish, shellfish, sea cucumbers, crabs, and even turtles provided high-quality protein and omega-3 fats. Octopus and eel were caught using intricate traps or passed down techniques involving stone enclosures. Coastal foraging and free-diving sustained communities where food was seasonal, sacred, and shared.

Fruits such as papaya, banana, guava, mango, and starfruit added vitamins and natural sweetness. Their fibre and low energy density protected against overconsumption. Fermented foods—whether from coconut sap or fish—added probiotics and preserved seasonal abundance.

These diets, though high in carbohydrate from roots and fruits, were low in sugar as we know it today. There was no refined fructose, no industrial oils, and no ultra-processed foods. Meals were labour-intensive, nutrient-dense, and metabolically protective.

The Pacific Islanders, especially those in Micronesia, Melanesia, and Polynesia, are among the world’s most genetically adapted to feast–famine cycles. One of the most consequential genes in this regard is ABCG2 (ATP-Binding Cassette Subfamily G Member 2). This gene regulates uric acid excretion through the kidneys and intestines. Variants of ABCG2 are common among East Asians and Pacific Islanders and impair uric acid clearance. In premodern contexts—where uric acid served as an antioxidant and survival molecule—this trait may have been advantageous. Following typhoons or cyclones, islanders could survive for weeks on fallen coconuts and reef fish, metabolically buffered by their genes.
However, in today’s world, the introduction of fructose into these populations has become catastrophic. Fructose metabolism increases uric acid production, and in individuals with ABCG2 variants, the body cannot excrete it efficiently. The result is a skyrocketing incidence of gout, kidney disease, and hypertension—diseases virtually unknown when traditional diets prevailed.

The Philippines provide a vivid example of gene–environment mismatch. Here, individuals often inherit a combination of SLC2A9 (uric acid retention), PNPLA3 (fat storage), and ABCG2 (reduced uric acid excretion) variants. When exposed to sweetened beverages, processed snacks, and Western fast food, the result is metabolic collapse—manifesting as gout, diabetes, fatty liver, and obesity at rates among the highest in Asia.

A revealing study published in PLOS ONE in 2019 described health practices on the remote Micronesian island of Pohnpei. It outlined 14 traditional markers of health—not just physiological indicators, but deeply embedded cultural practices.

These lifestyle markers reflected physical activity, ecological knowledge, community integration, and metabolic health. Where these practices persisted, so did health. Where they were replaced by electricity, imports, and convenience food, so too came the epidemics of obesity and metabolic disease.

“The healthy person has 14 features of healthy living.
Knows the name of their Nahnmwarki (local Chief)
Has a traditional title indicating societal rank
Has a traditional canoe
Family owns a canoe
Goes fishing
Follows the rules of the Nahnmwarki for fishing
Raises pigs for eating and to give as tribute to Chiefs
Has land
Grows crops on the land
House is made of traditional materials (local woods and grasses)
Pounds (prepares) sakau in the traditional way
Drinks freshly prepared sakau (made by pounding roots on the rock)
Uses traditional medicines
Built their own house, another house, or Nahs (feast house) with traditional materials.

The Pacific Islands are probably the clearest examples of dietary collapse. The climate of the area is the most idyllic in the world except for the typhoons that blow through every year. There are three genes common to these populations that are called “starvation” genes. They ensured that the populations survived long periods of near starvation after typhoons, with the only food available being fallen coconuts, seaweed, and anything swimming in the sea. After centuries of metabolic adaptation to their natural environment, their biology has been suddenly overwhelmed by sugar and processed food. As recent as the 1970s, diabetes and gout were rare. By the 2020s, they had become defining features of island health systems and the Western Pacific had the highest incidence of obesity in children and young adults in the entire world..

This transformation offers both a warning and a window. The further a society departs from its ancestral foodways, the more quickly its unique vulnerabilities are revealed.


3.8: Health: The Onset of Modern Diseases

Across every continent, traditional diets once maintained a delicate balance between food availability and human physiology. These diets evolved over millennia, shaped by geography, climate, and ecological opportunity. They were often modest in calories, rich in fibre, fermented or wild-harvested, and grounded in community. Most importantly, they were devoid of industrial sugars.

The modern world, by contrast, delivers food that is no longer bound by season or soil.
Refined sugar, high-fructose corn syrup, and ultra-processed foods have replaced indigenous starches, wild meats, and medicinal plants. The transformation has been global—and catastrophic.

Human physiology was never designed to handle unlimited refined calories. Our genes did not change in the span of a few decades, but our diets did. As one scientific review put it:
“Some factor of diet and/or lifestyle must be driving weight upward, because human biology and our underlying genetic code cannot change in such a short time.”

The driver is now well understood: a diet flooded with refined carbohydrates and industrial sugars, especially fructose. This mismatch between ancient genes and modern food lies at the root of the global metabolic crisis.

In societies that still consume ancestral diets—or lived on them until recently—conditions such as obesity, type 2 diabetes, fatty liver, and gout were historically rare. These diseases were almost unknown in 19th-century rural Asia, Africa, Oceania, or the Americas. Even in Europe and North America, prior to industrial food, they were limited to affluent individuals who overindulged.

But once sugar, flour, and processed oils entered the food supply, the picture changed rapidly. Populations that had never encountered refined fructose became the most vulnerable. Their genetic adaptations to past famine—once advantageous—now turned against them.
The PNPLA3 variant that once preserved energy in the liver now causes fat accumulation. The SLC2A9 variant that once conserved uric acid now triggers gout. The ABCG2 variant that protected against starvation now leads to renal failure when fructose intake is high.

The pattern is now unmistakable: Wherever Western food goes, Western disease follows.
The epidemiology confirms it. So does the biochemistry. So does the lived experience of elders who remember what came before. Whether in a rainforest village, an Arctic encampment, a rice-farming community, or a Pacific island, the arrival of sugar marked the beginning of decline.

In these traditional societies, food was a form of medicine. Now, food has become the disease.