We see the United States as the cradle of our supermarket culture, but there’s an Irish angle. It was the son of Irish emigrants who opened the doors of the first American supermarket on a hot day in August 1930.

The Great Depression had started, and Michael Cullen, who worked with the Kroger grocery chain, had an idea. He wanted to open a monstrous shop, according to Jonathan Mantle's book Companies That Changed the World. So Cullen wrote a letter proposing the idea, but a manager stymied the attempt, and his letter never made it to the bosses. Cullen quit in frustration, leased a vacant garage in Queens and opened King Kullen, which is often referred to as the world's first supermarket. His slogan was "Pile it high. Sell it low." Eighty-five years later the family-owned chain still operates 36 supermarkets on Long Island.

Kroger survived the loss of its disgruntled employee, followed his model and grew into the United States’ largest supermarket chain, with revenue of $103 billion, or €96 billion, last year.

Another pioneer had paved the way 14 years earlier. In 1916 a businessman called Clarence Saunders had opened the first (delightfully named) Piggly-Wiggly grocery store in Memphis, Tennessee. What made Saunders’s shop different was that it was self-service.

Until then shoppers arrived with a list for a clerk, who fetched the goods from behind a counter, bagged them and charged for them. Saunders’s clerks were cashiers only. Customers served themselves from the shelves. This allowed him to undersell his competition.

The self-service model combined with piling it high and selling it low to become an unstoppable force. In the Depression-era US, shoppers were willing to sacrifice the personal attention of a clerk for no-frills warehouses that stocked cheaper food. The unspoken pact that put value above shopkeeper relationships was forged.

Farm prices

The other Depression legacy was the 1933 US Farm Bill, brought in to stem crippling rural poverty by putting a floor under farm commodity prices. The twin systems of supermarkets and farm subsidies dramatically transformed food production in the United States. In 1935 it had 6.8 million farms. By 2010 it had only 2.2 million – but some of them were enormous. As American supermarkets grew into mammoth corporations, so did American farms.

It all started out so hopefully. In January 1955 Life magazine brought out a food issue with a cover that showed a smiling toddler in a supermarket trolley crammed with food packages. The magazine trumpeted the American dream; this was a country whose population had grown from 5.3 million in 1800, most of them subsistence farmers, to 163.5 million by the middle of the 20th century, when only 12 per cent of them were farmers.

It was on the face of it an incredible success story. Through ingenuity, clever logistics and hard work, people were freed from the tedious labour of feeding themselves. The system had created an alluring vision of plenty that could be replicated to ease poverty and hunger across the globe.

"Americans who are as well fed as any people in the world are also prize specimens of what good feeding does to a people," Life magazine declared. "Each generation is taller, bigger and healthier than the preceding one – and each has a longer life expectancy."

But there was a flip side to the agribusiness-and-supermarket model. Farm subsidies turned corn into cheap high-fructose syrup, which was packed into products piled high and sold low, alongside cheap grain-fed meat, two primary factors now blamed for chronic US obesity, whose medical costs are put at between $150 billion and $200 billion a year.

Life boasted in 1955 that supermarkets had "many new retailing tricks to take advantage of the fact that much buying is done on impulse. Related items like pancake mix and syrup are displayed together at eye level, while staples like bleach and floor wax are stored below. Meat counters are often placed at the rear, leading shoppers past the greatest possible number of shelves."

Five years after that issue of the magazine appeared Feargal Quinn opened Quinns Supermarkets in Dundalk in 1960. In 1966 Dunnes Stores, which had begun to sell clothes in the 1940s, opened its first out-of-town shopping centre, at Cornelscourt in south Dublin.

Retailing tricks

Since then supermarket culture, with its “retailing tricks”, has had a phenomenal effect on how our lives, towns and cities, farms and food systems are organised. We may be what we eat, but how we live now revolves around how we buy what we eat.

It’s a culture that has put the job of feeding millions of people into the hands of a small number of enormously powerful businesses. In 2009 the Department of Agriculture reported that retail chains in Ireland, “given their scale and market domination, have enormous bargaining power over producers. It appears they prefer to be supplied from one or two sources and they exert unrelenting pressure on producers to drive down prices.”

That pressure has had dramatic effects in rural Ireland. Teagasc, the agriculture and food advisory agency, has estimated that fewer than a fifth of beef farms are economically viable. Irish beef is processed by just three processors, all of which are pressing farmers to produce meat more cheaply and more quickly.

Grain silos are now a feature of most Irish beef farms, replicating the US model of fattening animals faster by taking them off grass. Dairy farmers face similar pressure to intensify production by housing their animals and feeding them more productive alternatives to grass, regardless of the wastefulness of feeding human food to animals.

When grainsand soya beans, among other foods, are fed to factory-farmed animals we have "farmageddon", according to Philip Lymbery of Compassion in World Farming, a group that aims to end factory farming. Lymbery's book Farmageddon details the hidden costs of cheap meat. He points out the waste that is created at every stage in the factory-farm-to-supermarket-shelf system. Eliminating that waste could free up enough food to feed a global population of 11 billion people, he argues.

Supermarket buyers have a world food basket from which to choose, with consequences for Irish-grown food. At the height of the boom of the early 2000s fruit and vegetable growers here were giving up trying to compete with cheap imports.

Between 2004 and 2008 the number of mushroom growers fell from 242 to 85, the number of growers of field vegetables, including potatoes, fell from 238 to 190. Outdoor-fruit growers fell from 104 to 72.

Supermarkets have changed farmers’ lives but also the food we eat. Even foods we think of as raw ingredients are processed to enhance their shelf life and appearance. Milk is homogenised – blasted through mesh to break up its fat globules – turning it into what some farmers call manufactured milk: a brighter liquid with a longer life.

Packets of supermarket meat contain not regular air but a modified, low-oxygen version that will keep it pink and attractive. Legislators have failed to keep up with clever packaging and with marketing terms such as “farm fresh”. Consumers are still not entitled to know, through labelling, whether the meat or milk they buy is from animals fed on grass. We still don’t have country-of-origin rules for processed pork, so “Irish” sausages can be made with Polish, Danish and Dutch pig meat.

Fresh fruit and vegetables are coated, waxed, stored for months in modified- atmosphere warehouses, and packaged to look their best. The enormous range of varieties of apples and potatoes has dwindled to a handful of key supermarket-friendly ones that look best on the shelves.

But supermarkets are going through torrid times. In 2013 the horsemeat scandal, exposed by the Food Safety Authority of Ireland, highlighted the complexity of food chains that lie behind the brightly lit fridges. Tesco's Everyday Value beef burger made at Larry Goodman's ABP plant in Ballybay, Co Monaghan, turned out to contain 29 per cent horsemeat. Tesco shares tumbled despite its "We apologise" advertisements.

German discounters

Just as supermarkets were Depression-era babies, so the Irish supermarket scene is now a product of the crash. Tesco, the dominant force here along with SuperValu (which took over the Superquinn brand) and the third player, Dunnes, lost out to the German discounters.

Lidl's market share grew from 6.4 per cent in 2012 to 8.8 per cent this year. Aldi was up to 8.6 per cent in the two years from 2012. Over the past 12 weeks Tesco and SuperValu have been neck and neck, with market shares of 24.5 and 24.4 per cent. Figures compiled by Kantar show we have moved away from the single weekly big shop captured in that Life cover. The 1.6 million weekly Irish shoppers spend an average of €104 a week on 58 items – not in one big trip but in 4.7 trips to at least two different supermarkets.

The discounter-and-second-shop combination is increasingly part of Irish habits. The main shop is now 38.8 per cent of the weekly spend, with “top up missions” accounting for 61.2 per cent.

So the big-box, out-of-town, park-and-load-up-for-the-week model that an Irish-American helped to invent has shifted. Tesco has learned the hard way that big is not what consumers seem to want any more. Dunnes Stores is showing signs of aspiring to become the Waitrose of Ireland, leaving the cheap-food sector to the discounters, at least in its more affluent neighbourhoods.

Supermarkets can be a force for good, which is why Compassion in World Farming works with them. The EU took 12 years to phase out battery cages for hens. Sainsbury's, Waitrose and Marks & and Spencer changed the trade more quickly by a consumer-prompted move to stock only free-range eggs.

The supermarket model could be said to reach its 100th birthday next year if we go back to Saunders’s Piggly Wiggly in Memphis. The personal service he abandoned in a race to value may now be built back into the model he helped to create.

Supermarkets may be struggling, but they are here to stay. As informed consumers we are powerful activists. We can vote with our weekly food budgets to get the kinds of supermarkets and the kinds of farms and food systems that we deserve.