Before Jamie Oliver there was Henry Fielding. Like the Naked Chef, the Tom Jones author was worried about the diets of England’s children. There may not have been turkey twizzlers in the eighteenth century but there were plenty of gin-addled mothers with malnourished boys, and Fielding fretted about “these wretched infants” becoming “our future sailors, and our future grenadiers”.

As Rebecca Earle, a historian of food at the University of Warwick, recounts in Feeding the People, Fielding was not the only one who was worried. The Enlightenment changed many things, among them the relationship between food and the state: “Everyday eating practices acquired a new political importance during the Enlightenment because statesmen and scientists, philosophers and philanthropists, became ever more convinced that there was a correlation between diet and national prowess.”

At the heart of this new food debate was the humble spud. Potatoes were so hyped as the key to a well-nourished populace by the European intelligentsia in the 1700s that Earle calls them an “enlightenment superfood” — the kale of its time. “For several years newspapers discussed practically nothing but potatoes,” claimed French historian Pierre-Jean-Baptiste Legrand d’Aussy in 1782. Adam Smith was a big fan, claiming that “the strongest men and the most beautiful women” ate potatoes.

Earle calls them an “enlightenment superfood” — the kale of its time

By the nineteenth century, however, the potato’s reputation had taken a knock. William Cobbett was among those leading the anti-spud charge. The cantankerous pamphleteer and Member of Parliament saw it as the cause “of slovenliness, filth, misery, and slavery” and threatened to sack any labourer caught tucking in to a potato. The argument was as much about the political and economic future as it was the foodstuff’s dietary merits.

To Cobbett, the potato stood for the intrusion of modernity into the rural way of life he cherished and what Earle calls the “proletarianisation and immiseration of working people”. In another corner of nineteenth-century debate, the potato was frowned upon not as a harbinger of the future, but as a relic of the past. Hardy potatoes had once been favoured as a source of national nutrition because of the ease with which peasants could grow them in their own gardens.

But the increasingly industrial and global version of capitalism that was ascendent called for the opposite of self-sufficiency. “The market economy demanded not merely healthy people, but a particular organisation of society around specific forms of waged labour and relations between employers and the workforce,” writes Earle.

The Irish famine loomed large, of course, and British liberals saw the fatal consequences of an over-dependence on a potato monoculture as a decisive blow for their side of the Great Potato Debate. The Treasury civil servant Charles Trevelyan, for example, described the famine, which claimed a million Irish lives, as a “glorious opportunity” to wean Ireland off potatoes and onto not just more modern diets but a more modern way of life.

Thomas Jefferson, who was more of a rice guy, once wrote that “the greatest service which can be rendered any country is to add a useful plant to its culture”. The evidence presented in Coffeeland, another book on the politics of food, suggests that there are at least exceptions to that rule. Augustine Sedgewick recounts the misery wrought by coffee growing on El Salvador and, in doing so, tries to tell a bigger story about “our favourite drug”, capitalism and globalisation.

At the heart of the story is James Hill, a Mancunian who set sail for the New World in 1889. After a commercially expedient marriage, Hill began growing coffee on the fertile slopes of the Santa Ana volcano, fine-tuning the process and eventually becoming one of the country’s largest producers of coffee, and the patriarch of one of las catorce familias, or 14 families, who ran El Salvador’s coffee trade and helped to corrupt its politics, with deadly consequences. Hill’s rags-to-riches story was built on the hunger of the thousands who laboured in his plantations. Whereas Adam Smith thought a successful economy was built on a well-fed workforce, Hill used hunger to get the most out of his workers. “To maintain the monopoly of basic human needs that drove people to work coffee,” writes Sedgewick, “he shaped the ecology of his plantations to route the sun’s energy toward coffee production, feeding his trees and starving his workers, producing coffee and hunger in corresponding amounts.”

Sedgewick’s account of Hill’s cruelty is chilling, but he is less convincing when he extrapolates from the cruelty on one 5,000acre plantation to make a bigger argument about capitalism. The lens through which Sedgewick presents the relation between bean, plantation owner and labourer is unambiguously Marxist. He swallows whole Marx’s long-ago rebutted labour theory of value and understands economic relationships in misleadingly extractive terms.

More than once, he reveals a disappointing romance for pre-coffee El Salvador, painting a patronisingly bucolic image of a contented peasantry tending communal land. Of early-nineteenth-century El Salvador, he writes, “The other side of the country’s commercial isolation was economic equality.” It is a strange thing to eulogise.

Notwithstanding its ideological limitations, Coffeeland is a stimulating book about the world’s favourite stimulant. Sedgewick delivers focused, compelling prose built on exhaustive research. His many detours are rich in detail and the reader is almost always repaid for taking the scenic route. Towards the end of Coffeeland, Sedgewick laments a missed opportunity in economic thought.

The nineteenth-century focus on energy “made it possible to establish the relationship between one person’s work and another’s in a newly direct way. Yet almost as soon as this possibility was raised, the calculations were deemed too complex, and it was abandoned.” It is an eccentric, engaging — and probably flawed — thought-experiment.

Both Coffeeland and Feeding the People tell the story of a foodstuff going global. Coffee was first grown commercially in Yemen in the sixteenth century. Within a few hundred years, it was traded around the globe. Potatoes were unknown to anyone beyond the Andes until around the same time, before coming to Europe with the conquistadors and spreading across the globe with European empires and merchants. These two products offer different visions of globalised capitalism.

Sedgewick understands the economic progress made over the last 200 years as “the division of the world into rich and poor” which “paralleled the division of the world into coffee drinkers, overwhelmingly concentrated in the industrialised global north, and coffee workers, even more concentrated in the predominantly agricultural and perpetually ‘developing’ global south.” Coffee fits Sedgewick’s approach because it is a valuable commodity over which developing countries have an almost total monopoly and therefore, Sedgewick argues, “is one of the most important commodities in the history of global inequality”. It is a trade that Sedgewick implies leaves everyone worse off. Coffee is a work drug necessitated by capitalism, he argues, glugged down by sleep-deprived, stressedout workers in the developed world.

Earle’s surprisingly rich history of the potato, by contrast, is about a carbohydrate whose spread around the world didn’t just power the people, but was the source of considerable people power. In eighteenth-century England, potatoes allowed working people to dodge tithes. In twentieth-century India, nationalists promoted the potato as a way to “strengthen Indian bodies”, meaning, as Earle explains that “a symbol of British superiority became a tool for ending colonial rule”.

During China’s great famine, “the state requisitioned grains but not vegetables, and therefore not potatoes”, meaning the villages that grew potatoes had an extra line of defence against Mao’s regime, and fared significantly better than the ones that did not. (James Hill would surely have hated potatoes.)

Given that they grow more or less anywhere, and don’t generally make it far before they are eaten, potatoes tell us relatively little about global trade. Potato markets’ immunity to global price fluctuations is why development agencies increasingly see the vegetable as an important source of food security.

But potatoes do reflect the flattening and homogenisation that has come with globalisation. Above all, past bust-ups over the spud — self-reliance and security versus specialisation and trade, modernity versus conservatism — remind us that our present fault lines are nothing new.