Passage 1

Nutrition is fundamental to human life. Every cell in the body relies on energy and nutrients from food. However, the idea of a healthy diet has changed dramatically through history, and understanding this evolution helps explain current dietary problems.

For most of human history, people lived as hunter-gatherers. Although their diets varied by region, they were generally diverse, comprising wild plants, fruits, nuts, seeds, lean meat and fish. These diets were rich in dietary fibre and protein, while sugar and salt were scarce. As a result, chronic diseases such as type 2 diabetes and heart disease appear to have been uncommon.

Around 10,000 years ago, the agricultural revolution transformed nutrition. The domestication of cereals and animals allowed settlements and food surpluses, enabling population growth and civilisation. Yet the new agrarian diets were less varied than those of foragers. People depended heavily on just a few staple crops, and skeletal evidence suggests that early farmers often suffered from nutritional deficiencies, dental decay and infectious diseases. Living in dense communities and working with domesticated animals encouraged the spread of pathogens. In some regions, average height actually declined after farming began.

The next major shift came with the Industrial Revolution. New technologies permitted fine grain milling, cheap sugar production, and mass preservation. These innovations reduced shortages but also changed food quality. Refined flour lost much of its fibre and many micronutrients, and manufacturers added salt, fat and sugar for taste and shelf life. Diets consequently became energy-dense but nutrient-poor, creating a basis for non-communicable diseases.

The twentieth century brought an even deeper change known as the 'nutrition transition'. This is the shift away from traditional, minimally processed diets towards Western dietary patterns heavy in animal products, refined grains, added sugar and unhealthy fats. The transition is driven by urbanisation, rising incomes, food marketing and supermarket expansion. Importantly, it is not confined to wealthy countries; many low- and middle-income nations have adopted these eating habits within one generation.

One consequence is the 'double burden' of malnutrition. Many developing countries still face undernutrition and micronutrient deficiencies among the poor, while overweight, obesity and related diseases grow among other groups. This combination places great pressure on health systems and requires policies that tackle both problems.

Nutrition science is relatively young. Early twentieth-century discoveries of vitamins showed that diseases such as scurvy and rickets were caused by nutrient deficiencies. Later epidemiological research linked dietary habits to chronic disease. Governments began producing dietary guidelines, often presented as food pyramids, that promoted fruit, vegetables and whole grains while limiting saturated fat, salt and added sugar.

Despite these efforts, global diets have worsened. Since the late twentieth century, ultra-processed foods have become a major source of calories worldwide. These are industrial formulations made from cheap ingredients such as refined starches, hydrogenated oils and artificial additives. They are convenient, palatable and intensively marketed, and growing evidence connects them to obesity and chronic disease.

Fixing modern nutrition requires more than personal responsibility. A food systems approach is needed, integrating agriculture, food processing, trade, marketing and the environment. Possible measures include sugar taxes, clearer food labels and restrictions on advertising to children. Personalised nutrition is also emerging, using genetic and microbiome data to tailor dietary advice. Sustainability is now part of the agenda too, since food production affects climate, water and biodiversity. In the future, healthy diets for a growing population will depend on reconciling nutritional science with ecological limits.