In the spring of 2018, New York was gripped by a sudden, very particular and, for some, calamitous food shortage. Gaps appeared on grocery shelves. Coffee shops put out signs, turning customers away. Twitter and Instagram brimmed with outrage. The truly desperate searched from Williamsburg to Harlem, but it seemed undeniable: New York was out of oat milk.

It wasn’t just New York, in fact. The entire US was suffering from a shortage of Oatly, a Swedish plant milk whose rapid rise from obscure digestive health brand to the dairy alternative of choice had caught even Oatly by surprise. Since its US launch in 2016, Oatly had gone from supplying a handful of upscale New York coffee shops to more than 3,000 cafes and grocery stores nationwide. The company had ramped up production by 1,250%, but when I spoke to CEO Toni Petersson in late summer, they were still struggling to meet demand. “How do we supply when the growth is this crazy?” Petersson said.

Fortunately, when it comes to milk, in 2019 there is no shortage of alternative alternatives. Visit your local supermarket and you will find a refrigerated aisle overflowing with choice: almond milk, hazelnut milk, peanut, tiger nut, walnut, cashew – and that’s just the nuts. Coconut, hemp, spelt, quinoa, pea – you name it, somewhere a health-food startup is milking it. London tube stations are filled with ads for new plant milks – or rather, “mylks” (EU law prevents dairy alternatives from using the word milk if it isn’t produced by a lactating mammal). Cookbooks dedicate entire chapters to blending and straining your own. Sainsbury’s now stocks around 70 different options. There are the wellness punks (Rebel Kitchen, Rude Health), the dairy puns (Malk, Milkadamia, Mooala) and the nourishers (LoveRaw, Good Karma, Plenish). “People are just looking at every nut that exists and seeing if they can squash it into a milk,” said Glynis Murray, one of the owners of Good, which squashes hemp seeds into oil and milk.

It seems unthinkable now, but as recently as 2008, alternatives to cow’s milk largely meant soya (invariably Alpro in the UK, Silk in the US). For anything else, you’d need to scour health-food shops for drab, clinical-looking, long-life cartons of rice milk buried in the back with the other digestive aids. “It was the deathly aisle,” said John Schoolcraft, Oatly’s global creative director. “It was just for people who were lactose intolerant [or] had an allergy to milk; vegans, vegetarians – people who, at that time, were on the fringe of society.”

Plant milks are no longer fringe. Just over one in 10 of Pret a Manger’s hot drinks in the UK are ordered with dairy alternative milks (organic soya milk or organic rice-coconut milk). According to research firm Mintel, UK plant milk sales have grown by 30% since 2015, buoyed by a surge in vegan and vegetarian diets. In the US, nearly half of all shoppers now add a plant milk to their baskets. Globally, the industry is estimated to be worth $16bn.

Meanwhile, reduced demand for cow’s milk and falling prices led to the closure of 1,000 dairy farms in the UK between 2013 and 2016. Milk’s reputation as a healthy food is under threat from anxieties about bovine antibiotics, animal cruelty and the industry’s environmental impact, as well as increased diagnosis of lactose intolerance. Teenagers now consider cow’s milk less healthy than plant milk alternatives, a development the former chairman of Dairy UK, David Dobbin, called “a demographic time bomb”.

“Consumers are really not sure about the dairy industry,” Caroline Roux, a dairy analyst at Mintel, told me. “They’re not convinced these products are good for them any more.”

But the plant milk boom is, as one entrepreneur told me, “way bigger than just switching your milk”. To converts, almond and oat milk are the next wave in a fundamental shift towards a more conscious, sustainable way of living. To critics, they’re little more than cleverly marketed nut juice with additives – a symptom of everything that’s wrong with modern food culture. And so a strange battle has emerged, between an industry trying to replace something it says we don’t need in the first place, and dairy, a business that for a century sold itself as the foundation of a healthy diet, while ignoring the fact that most of the world does just fine without it.

We are all born milk drinkers. Babies’ guts produce the enzyme lactase, which breaks down lactose, the sugar in breastmilk (and cow’s milk), into the simpler sugars glucose and galactose. But for the majority of humans, production of the enzyme lactase plummets after weaning. “From a human perspective – no, to go further than that, from a mammalian perspective – the norm is to be able to tolerate your mother’s breast milk, and then as you get past infancy, to stop producing lactase and become lactose intolerant,” said Adam Fox, a consultant paediatric allergist at Guy’s and St Thomas’s hospitals, and one of the UK’s leading food allergy experts. “Then you’ve got a small group of humans that have a mutation which means they maintain production of lactase into adulthood. Northern Europeans, the Masai [in east Africa], some Arab groups as well. But that’s the exception, not the rule.”

That schism between milk-drinkers and the rest – actually a series of independent genetic mutations – appears to have occurred about 10,000 years ago, around the time humans were domesticating farm animals. It is the reason that in countries such as the UK, Sweden and Ireland, more than 90% of adults can drink milk without suffering any ill effects, but worldwide, more than two-thirds of all adults are considered lactose intolerant. For lactose-intolerant people, a glass of milk can induce bloating, stomach pains and diarrhoea. (Lactose intolerance should not be – though often is – confused with cow’s milk allergy, an immune response to the proteins in cow’s milk that affects around 1% of UK adults.)

Even in northern Europe, milk as we know it is a recent phenomenon. Fresh milk, left unrefrigerated, spoils quickly and can harbour a variety of deadly pathogens, including E Coli and tuberculosis. For most of history it was either consumed within moments of milking, or processed as cheese or yoghurt. Few drunk milk in its liquid form. “The Romans considered it a sign of barbarism,” said Mark Kurlansky, author of Milk! A 10,000-Year Food Fracas. “The only people who drank milk were people on farms, because they were the only ones who could get it fresh enough.” (Even then, cow’s milk was considered inferior to alternatives such as goat or donkey.) In the 19th century, “swill milk” – so called because cows were fed the filthy runoff from inner-city breweries, turning their milk blue – was linked with thousands of infant deaths. Only in the early 20th century, with the introduction of mandatory pasteurisation – in which milk is heated to kill off any bacteria before bottling – did milk become safe enough for most people to drink regularly.

Cows being machine-milked in France in 2017. Photograph: Philippe Huguen/AFP/Getty Images

It was the first world war that ultimately aligned political forces behind the dairy business. In Britain, rationing meant food was limited, and child malnutrition was rife. The emerging field of nutritional science identified milk – with its high protein content and newly discovered “vital amines”, or vitamins – as a potential solution. Thanks to government price controls, milk was one thing not in short supply. Soon, “consumers everywhere witnessed a snowfall of propaganda documenting the miracles worked by milk”, writes Deborah Valenze in Milk: A Local and Global History. Milk became the original superfood: a boundless source of calcium, protein and vitamins. In 1946, Clement Attlee and Harry S Truman’s governments both passed measures to ensure milk was available free with school meals. Industry alliances like the UK’s Milk Marketing Board embarked on campaigns to enhance milk’s image. More recently, in the US, the Got Milk? campaign showed celebrities from Beyoncé to Kermit the Frog with milk moustaches. The message was clear: if you wanted your children to grow up big and strong, they needed to be drinking milk.

Today, dairy is a vast and highly regulated behemoth, worth more than $400bn, produced by a global herd of more than 274 million cows. Politicians mess with milk at their peril (when Margaret Thatcher, as education secretary, in 1971 took the draconian step of cutting free school milk for the over-sevens, she was branded “milk snatcher”). And yet, for many consumers, the allure of milk is on the wane. In 1975, the average American consumed 247 pounds (around 130 litres) of milk per year; in 2017, it was just 149 pounds (66 litres). In the US, milk sales have fallen 15% since 2012.

Milk’s “share of throat” – an industry term for the proportion of total liquid we consume in a day – has been eroded by a steady flow of soft drinks, juices and smoothies, even bottled water. But none of these presented an existential threat. Blanket marketing established the connection between milk and wholesomeness and good nutrition. Now new forms of persuasion, more targeted and pervasive, have stripped away that healthy sheen from dairy.

The internet has given animal rights activists new reach. Search for “dairy” on YouTube and you will be assaulted by videos with titles like Dairy Is Scary (5m views), which depicts in graphic detail the suffering of dairy cows. Netflix, too, has provided previously untapped audiences for documentaries like Cowspiracy and What the Health. Besides the ill-treatment of animals, evidence has mounted that the dairy industry is catastrophic for the environment. Animal agriculture contributes more greenhouse gases than aviation, shipping and road vehicles combined. One recent study led by Oxford University claimed that observing a vegetarian or vegan diet is the single most effective way to reduce your own environmental footprint.

Plant milks received a boost from their association with clean eating, a craze that has also had the effect of linking dairy with negative health issues. Clean eating, advocated by a fresh-skinned, glossy crop of wellness bloggers and Instagram celebrities, argued for the elimination of any foods deemed overly processed, allergenic, or otherwise “unnatural”: gluten, caffeine, meat and dairy. Its proponents blamed lactose intolerance as the cause of a range of ailments, including acne, eczema, lethargy, joint pain and a variety of digestive issues. And, as the clean eaters warned their readers off dairy, they sent them into the willing arms of plant milk startups. A steady supply of attractive millennial influencers filled their Instagram feeds with appetising shots of peanut-milk Thai curries and gluten-free beetroot bread. (According to industry analysts, one of the keys to the plant-based trend is that it looks appetising on Instagram.) The clean eaters did what years of vegan campaigning never could. Suddenly, giving up milk wasn’t just a health issue. It was part of living your best and most beautiful life.

The notion of milking plants is not new. In China, soya milk has been made since at least the 14th century, most commonly as a step in making tofu. The earliest written mention of almond milk appears in a Baghdadi cookbook from 1226, the Kitab al-Tabikh. “If you look at Medieval recipes, they will often give you a choice between milk or almond milk,” said Mark Kurlansky (whose best-seller Cod: A Biography, launched an entire genre of food microhistories).

In the west, until recently, almond and soya milk remained relatively unknown, except by vegetarians and the odd eccentric (Henry Ford, of the car company, was an early soya evangelist). In 1956, the Plantmilk Society was established in London by Leslie Cross, then vice-president of the British Vegan Society, a nascent group of animal rights activists. Cross, who particularly objected to the cruelty of the dairy industry, set about trying to find a dairy replacement using crops that could be grown in Britain.

“The big issue originally was: how do you get a protein in a liquid that can emulate dairy milk?” said Adrian Ling, whose father, Arthur, was chair of the new organisation. Photos from the time show the smiling pioneers in white lab coats examining many glasses of questionable opaque liquids. “They did a lot of work on cabbage,” Ling said. Eventually, they settled on the soya bean. “It was a very small market – a few hundred people,” said Ling. “They lost a lot of money.”

In 1981, a young Belgian food tech named Philippe Vandemoortele decided to use a new packing technology, the sterile Tetra Brik, to sell soya milk. “I started in a garage with pots and pans, a grinder. I was young, and very naive,” Vandemoortele, now 73, told me. He called his soya milk Alpro. Reviews were mixed. The local supermarket refused to stock it. “The buyer tasted my product, and he said: ‘Whoa. It’s awful!’” But Vandemoortele persisted. Today Alpro is owned by Danone, and in 2017 had a turnover in excess of £183m.

Soya’s real break came in the late 90s, when a Colorado soya company called WhiteWave made what seems like a confoundingly obvious discovery: if they moved the product to the refrigerated aisle alongside the dairy milk, more people bought it. WhiteWave’s new refrigerated soya drink, which it called Silk, was a sensation. At the same time, Silk, Alpro and others jumped on emerging evidence about the link between high cholesterol and heart disease to market themselves as a healthy alternative. All of a sudden, soya was for everyone.

Soya’s rapid growth was short-lived, in large part due to the fact that it doesn’t taste very good. Even modern soya milks, which add sugar, thickeners and other additives to imitate dairy milk, have a beany taste and odour. In the early 2000s, soya had its own health scare. Soya contains phytoestrogens, oestrogen-like compounds that can mimic the hormone’s effects in humans, a discovery that led to fears about it disrupting hormones and “feminising” men. Clinical studies have consistently shown those fears are overstated. Even so, neo-Nazis continue to push the theory that soya milk is a liberal conspiracy to emasculate men, and drink cow’s milk at rallies to demonstrate “digestive superiority”.

In 2008, the Blue Diamond Growers, a large cooperative of almond farmers in California, sensed an opportunity. Its milk, Almond Breeze, had long lagged behind Silk, by then America’s leading soya brand. “We knew if we were wanting to compete with them, we would need to be in the refrigerated case,” Al Greenlee, Blue Diamond’s director of marketing, told me. Supermarkets maintain a tight grip on shelf space, charging high fees to stock a new product. Lucrative, high-traffic displays like the refrigerated case are fiercely competitive. The owners of Silk at that time – the dairy giant Dean Foods – had leveraged its industry clout to get Silk positioned alongside milk. “So we followed a similar path, and established a partnership with the second largest dairy in the country”. Blue Diamond started in Florida, targeting neighbourhoods with large Hispanic populations, who have a higher genetic incidence of lactose intolerance.

Meanwhile, the California almond industry embarked on a vast marketing spree, funding – and publicising – new research into the health benefits of almonds. The effect was immediate. Glossy magazines proclaimed almonds a “superfood”. Almond Breeze was so successful that within two years Silk launched its own almond milk to try and keep up. By 2013, almond had overtaken soya as the best-selling plant milk in the US.

In today’s crowded market, newcomers require something special to stand out. An Australian milk called Nutty Bruce boasts of “activated almonds”, which is a nod to the current craze for charcoal (superheated and then oxidised, “activated” charcoal is marketed as a detoxifier), but at closer inspection just means the almonds are soaked in water for slightly longer than usual. A San Francisco startup called Ripple claims to have developed a hi-tech process to isolate the protein in yellow peas without any of the associated flavours or colourings. Cheryl Mitchell, the chief scientist of the New York-based producer Elmhurst Milked, told me excitedly about her patented extraction process, which uses “high-pressure water and a sloughing action” to break down nuts and pulses while keeping the proteins intact.

Mitchell comes from an esteemed line of food technologists: her father, Bill, invented Cool Whip imitation cream, the Pop Rocks popping candy and Tang fruit-flavoured drink. In the 1980s, she helped develop Rice Dream. Elmhurst was a dairy for 90 years; at its peak, it supplied public schools and Starbucks branches across Manhattan. But in 2016, its owners sold off the cattle and switched to plant milk. It now sells 11 varieties. “Wait till they see the corn milk,” she said. “It’s yellow, but it has more antioxidants than blueberries!”

It seems every ingredient has its acolytes. “We are here to spread a philosophy about a way of being, one which is much more harmonious and symbiotic with nature,” Tamara Arbib, the founder of London-based coconut drinks company Rebel Kitchen, told me. Rebel Kitchen’s Mylk, launched in 2014, is a blend of coconut, rice and cashew. “I’m a massive fan of eating right for your blood type,” Arbib said. “A lot of blood types do better without dairy.”

In July, I went to see one of the UK’s most prominent plant milk startups, Rude Health, in London. Launched by Camilla and Nick Barnard in 2005, Rude Health started out selling muesli, but quickly grew into a small health food empire. It was the tail end of a heatwave, at brunch time, and the Rude Health Cafe hummed with healthy looking professionals sipping cashew lattes. Nick, who has sharp features, grey hair, and wore an open-collared white shirt, ordered a kombucha. “I’m having dairy,” Camilla said, conspiratorially.

Rude Health had attracted negative press in 2017, after some vegans became incensed at a company blogpost promoting sustainable dairy. “It hadn’t crossed our minds that to be for dairy free, we were expected to be against dairy,” Camilla said. “We were just chugging along, thinking we were for good quality.” The episode had made them reconsider their marketing strategy, to clarify that they’re not an exclusively vegan brand. “Why does everything have to be the magic pill, or the devil? Why do you have to be for or against?”

Rude Health got into plant milks in 2013, selling three flavours: oat, brown rice and almond. Today, it sells 10, including Tiger Nut, Cashew and Hazelnut & Cacao. We walked over to the company’s offices nearby for a tasting session. Rival products and plant-based cookbooks lined the shelves. Nick poured shots of various shades of beige into small glasses. Many plant milk brands add calcium carbonate – chalk – to make the liquid whiter and more opaque (the calcium content is a happy bonus) but the colouring in these plant milks, Camilla assured me, was natural. We tried a few. The coconut was sweet, like a Bounty dissolved in water. The hazelnut was pleasingly thick, if slightly overwhelming. “Tondo Gentile,” Nick said, approvingly. “A gourmet hazelnut.”

The almond tasted thin by comparison. The brand’s regular Almond Drink contains brown rice, “cold-pressed” sunflower oil and sea salt, but Rude Health also offers Ultimate Almond – just nuts and water – intended for purists. “There is a hardcore market,” Camilla said.

Today, almond makes up around two thirds of all plant milks sold, but it is suffering its own reputational crisis. One issue is environmental: it takes 4.5 litres of water to grow a single almond (technically not a nut, but a seed). In California, which grows eight in 10 of the world’s almond crop, almond growing consumes an estimated 10% of the entire water supply – a controversial issue in a state often afflicted by drought.

Consumers have also caught on that the actual almond content of most almond milks is minuscule. Both Silk and Alpro contain just 2% almonds. “It’s actually a water-based emulsion that you’re adding oils, a lot of sugar and gums to, and then just adding a couple of nuts on top,” Elmhurst’s Cheryl Mitchell said. “As a business model, it’s great – any time you can sell water, right? That’s essentially what they’re doing.” The industry insiders I spoke to agreed that almond’s moment is over. Right now the real growth is in coconut, and in oat.

In 2012, when Petersson took over as CEO of Oatly, almost nobody had heard of oat milk outside Sweden. The company was founded in 1994 by Rickard Öste, a researcher at the university of Lund. “It’s a really good crop. You can grow oats everywhere,” said Petersson. “It has carbs, it has fat, it has protein and it has fibre.” Compared to oat milk, he said, almond is just “flavoured plant juice”.

‘Welcome to the cult’ … an Oatly marketing campaign. Photograph: Oatly

Petersson, who is 50, with dark hair and slim features, set about reinventing oat milk’s image. He hired John Schoolcraft, a marketing and advertising executive who had been running his own company, to help him. The concept, Schoolcraft said, was simple: “If you’re not lactose intolerant, why would you notice our product?” The pair redesigned its packaging, ditching its previous generic, 1990s aesthetic for a brash, millennial-friendly redesign: Oatly was restyled as Oat-ly! and the side of each carton displayed one of more than 80 messages written by Oatly staff, which congratulated readers on being part of the “post-milk generation” and, only semi-ironically, joining “the cult”.

Oatly’s real masterstroke was the creation of its Barista Edition. Most plant milks split in hot drinks – one reason that so many manufacturers use acidity regulators and other additives – and don’t foam like cow’s milk (the problem is the plant proteins). There, Oatly has an advantage: it foams, and the taste of oat is mostly masked by the coffee. Petersson and Schoolcraft ignored supermarkets and targeted coffee bars in the hip neighbourhoods of Brooklyn in New York and Shoreditch in London. “The volume comes from retail, but the demand is created in coffee shops,” Petersson explained. “That’s where you try our product and experience oat for the first time, in an environment that you like.”

“It blew my hair back,” said Stuart Forsyth, a former barista and the co-founder of vegan coffee brand Minor Figures. “Oatly made oats sexy.”

Oatly’s growth hasn’t been without controversy. In 2015, the Swedish milk industry sued it, claiming its ad slogan “Like milk, but made for humans” unfairly denigrated cow’s milk. Oatly lost, but Petersson and Schoolcraft continue to use the slogan outside Sweden. “The line implies what everyone already knows. Milk is produced by cows for the benefit of baby cows,” said Schoolcraft.

Whether or not plant milks really are a healthy substitute for cow’s milk is a matter of fierce debate, and not an inconsequential one. In June 2017, a Belgian couple were convicted of unintentionally causing the death of their seven-month-old baby, after feeding him oat and quinoa milks instead of infant formula. The parents, who ran a health-food shop, believed the child was lactose intolerant and sought the advice of homeopaths rather than seeking medical attention.

Much of the debate revolves around whether or not plant milks should be fortified with additional vitamins to better imitate cow’s milk. Oatly fortifies its product according to WHO guidelines. Rude Health doesn’t. “The minute you start fortifying, you’re pretending it’s milk,” Camilla Barnard told me. “I don’t want to do that. It feels dishonest.” Because the Soil Association refuses organic certification to fortified products, many new plant milks choose the “purity” (and associated high price) of organic over the use of additional nutrients. Califia Farms’ unsweetened almond milk boasts “50% more calcium than milk” on its bottle – but it doesn’t contain Vitamin D, B12, Riboflavin or any of the other nutrients found in milk or other fortified plant milks.

“A consumer has to read the label and understand the variation that exists in these milks, because they range tremendously,” said Dennis Savaiano, a professor of nutrition science at Purdue University who has studied milk for more than 30 years.

What most plant milks are desperate to tell you is what they don’t have in them. Dairy-free; sugar-free; soya-free; gluten-free; GMO-free; bisphenol A-free – in some cases, the “free from” declarations are actually longer than the ingredients list. Califia Farms boasts its products are carrageenan-free, despite the widely used stabiliser being approved as safe by the European commission, the US Food and Drug Administration and the WHO. It’s the inevitable culmination of today’s anxious eating culture: we’ve gone from buying foods on the merits of their ingredients, to buying them on the basis of what’s left out.

“If you look at our category, it’s a little bit messed up, you know?” Petersson conceded. “What’s the definition of an oat milk? Think of the comparison between oat milk and soya milk and almond or rice – are those all plant-based milks, or not? Nobody really knows.”

To protect against such uncertainty – and protect the dairy industry from the upstarts – a US senator from Wisconsin sponsored a bill in 2017 called the Dairy Pride (Defending Against Imitations and Replacements of Yogurt, Milk and Cheese to Promote Regular Intake of Dairy Everyday) Act, which would ban plant drinks from impersonating dairy.

“No one is necessarily drinking milk for the nutritional benefits of it,” said Tamara Arbib of Rebel Kitchen. “When you’re an adult, you’re having it because you want something creamy in your drinks.” It is true that our postwar worries about child malnutrition have been replaced with fears about childhood obesity. And the two-thirds of the world that can’t drink milk aren’t suffering from osteoporosis or rickets; in fact, China and Japan have lower rates of these conditions than Europe.

“A lot of scientists think this thing about how children have to drink cow’s milk is bogus. This idea that it makes you big and strong is clearly bogus,” Mark Kurlansky, the food historian, told me. “On the other hand, this idea that ‘milk is bad for you so I’m going to have almond milk or soya milk or something’ – that’s bogus, too. Because it’s a totally different food.”

Every nutritionist I spoke to emphasised that milk is no less healthy than it’s ever been; in fact, it’s never been safer. “From a scientific perspective, the data that suggests milk is a bad food just doesn’t exist,” said Savaiano. “It has a lot of nutrients in it. It’s a great source of calcium, it’s a great source of protein, it’s a good source of riboflavin and potassium. So you can’t make the argument it’s not a nutritious food.” Nor could any health professional I spoke to point to any data showing a confirmed rise in diagnosed lactose intolerance, though most agreed that cases of self-diagnosis are rising.

But the plant milk boom is not really about nutrition. Nor is it the first wave of a shift towards ethical, plant-based living – much as we need it. “Those other things might be on people’s lists, but they’re secondary selling characteristics,” explained Julian Mellentin, director of New Nutrition Business, a food industry analyst firm that has tracked plant milk’s rise. He pointed out that 90% of plant milk buyers still purchase other dairy products, like cheese and ice cream, both of which are still growing. The forces driving us towards plant milk are really something bigger: a manifestation of a collective anxiety that something is wrong with our bodies. That we aren’t as healthy and happy as we could be – or perhaps, should be – and something, or someone, must be to blame.

“There’s a lot of people discovering dairy intolerances and gluten intolerances and that kind of stuff, but actually I think what you’re looking at is much more intolerance to the life we’ve been living,” said Arbib.

Our growing suspicion of milk is perhaps a symptom of a lost faith: in Big Agriculture, in nutritional science. “People have learned that dietary advice changes,” Mellentin said. First saturated fat was killing us, now sugar is the number one enemy. Eggs and nuts were sources of bad cholesterol, now they’re superfoods. “So, understandably, people have become sceptical,” Mellentin went on. “Why listen to an expert when they change their mind all the time?” It doesn’t matter that that is how science works. Science changes, so who’s to say that your blood type doesn’t affect your dairy tolerance, or that carrageenan wasn’t the reason for some unspecified malaise? Just because our newfound lactose anxiety isn’t necessarily medically diagnosable, Mellentin said, that doesn’t mean it should be written off. “It’s not to do with allergies. It’s to do with how people feel, and making themselves feel better,” he said. How can you argue with that?

Recently, Oatly has begun eyeing plant milk’s next target: China. It launched in the country in 2016, after receiving an undisclosed investment from a Chinese conglomerate. Sales have been promising. Demand for milk in China is growing, and Chinese businesses are investing heavily in plant milk and lactose-free alternatives. To Oatly, conquering China is more than business, it’s an ethical obligation. “The worst thing that could happen [environmentally] is if the Chinese people started to drink dairy milk, because there wouldn’t be enough cows in the world to support that,” said Toni Petersson, the CEO. The company’s latest challenge is competition: Quaker has announced plans for a line of oat drinks, and in January Silk launched its own oat brand, Oat Yeah. “We think oats can become its own category,” Petersson said.

Other plant milk entrepreneurs were more cautious. Everyone knows how quickly health-food hype – juice cleanses, coconut oil – can die off. Meanwhile, kombucha is gaining ground as the gut-friendly food cure of the moment. Mellentin was blunt: “Peak plant milk is about three to five years away, at most.”

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• This article was amended on 29 January 2019. An earlier version stated that Winston Churchill introduced free milk to schools in 1946. Clement Attlee was prime minister at that time, and it was his government that passed those measures.