Truth about milk: What Oxford scientists say can fight cancer, the secrets of ultra-processed products... and the ones that will make you put on weight without realising, revealed by experts

Perhaps the pushback began in earnest in 2023, when model Hailey Bieber, who'd previously espoused a mostly plant-based diet, posed for her 50 million Instagram followers wearing a T-shirt emblazoned with the dairy industry's campaign logo, 'Got Milk?'

An improbable slew of young dairy-farming influencers were next, stalwartly defending the white stuff. And then, last week, the knockout blow.

Not the University of Oxford research that found drinking one large glass of milk a day is linked to a 17 per cent reduced risk of bowel cancer. Or the other study that concluded those who drank plant-based milk were at a higher risk of both anxiety and depression compared with dairy drinkers.

No, the cow's milk comeback was sealed when Nicole Kidman stood up to accept a Best Actress award for her film Babygirl in New York – and celebrated by downing a glass of milk on stage. In the movie, a young intern uses cow's milk to seduce Kidman's CEO character, raising the shocking prospect that milk is now sexy.

The scene, which has caused almost Saltburn levels of uproar, was based on an incident that happened to the film's director, Halina Reijn. She says she found it both 'courageous' and 'hot' when a young actor ordered a glass of milk for her at a bar. As for Kidman, she told an interviewer: 'I really like milk.'

It's an unlikely moment for milk to be in the limelight, given that ONS data shows our average consumption of cow's milk has fallen by 50 per cent since 1983.

The dairy decline started due to concerns over whole milk's (modest) fat content among dieters, and by the 2010s milk was derided at every turn – by vegans for being cruel to cows, by environmentalists for the impact of dairy farms on global warming, and by everyone in between who insisted it was downright weird to drink the milk of an animal.

Meanwhile, trendier, apparently more virtuous 'plant milks' soared in popularity, prompting a bitter war that both sides have milked for all it is worth.

Swedish manufacturer Oatly landed the first punch in 2014, with its advertising strapline 'It's like milk, but made for humans'. Dairy company LRF Mjolk sued Oatly for smearing its product and won – but the publicity saw Oatly's sales rise and a new dawn of milk substitutes emerge.

Suddenly every conceivable nut, vegetable and grain – from rice and pea to potato – was being pulped and sold for profit. Wellness guru Gwyneth Paltrow was an early proponent of almond milk – added to kale smoothies, of course. And suddenly plant milks were a lifestyle choice, with oat lattes clutched by manicured post-Pilates hands on every aspirational social media feed.

In 2015, Starbucks added coconut milk to its menu. By 2019, more than one in ten of Pret a Manger's hot drinks were ordered with dairy alternatives.

Soon ordering your latte with plain old cow's milk was about as socially acceptable to a squeamish Gen Z as streaking. One study found that those over 65 drank around three times as much milk as those aged five to 24.

Even so, cow's milk was still significantly cheaper than plant alternatives. Today a litre costs £1.20 in Sainsbury's, compared to £2.10 for the equivalent oat drink – a critical difference in the cost-of-living crisis. So perhaps it's not surprising that sales of whole milk grew by 2.5 per cent last year, just as we began to wonder if cow's milk might be healthier than plant-based alternatives, too.

After all, don't some of the latter fall into the category of – whisper it – ultra-processed foods? Take oat milk. It makes for such a rich, creamy, satisfying coffee because it often contains an acidity regulator to stop it separating when added to hot drinks.

Added oil also sometimes gives plant-based milks their creaminess, 'and many contain thickeners, gums and emulsifiers to give a creamy mouth feel and frothiness', says nutritionist Laura Southern of London Food Therapy. She adds: 'Milk is far from perfect, but it's more natural than the alternatives.'

Cow's milk is, of course, high in calcium – essential for healthy bones and teeth, as well as linked to a reduced cancer risk. And while many plant substitutes are fortified with calcium, 'when calcium is added in synthetic form, our bodies find it more difficult to absorb', says Southern.

Typically, oat milk has just under a third of the protein content of semi-skimmed cow's milk (1.1g versus 3.6g per 100ml) – and a third more carbs (7.1g versus 4.8g per 100ml).

Jessie Inchauspe, the biochemist better known as the Glucose Goddess, scathingly explains – in a clip now viewed more than four million times on TikTok – that 'oats are a grain, and grains are starch', and so oat milk is 'juice with a lot of glucose in it. So it leads to a big glucose spike'.

What about the other plant-based substitutes? Nut milk is among the most natural, but Alpro's Almond No Sugars long-life dairy-free drink, for example, still contains two stabilisers and an emulsifier.

Certainly, protein – essential for building muscle – is one of milk's wonder ingredients. One study of 1,456 women aged 70 to 85 in the Journal of the Academy of Nutrition and Dietetics found that those who drank the most milk had 'significantly greater' muscle mass. Research has also linked whole cow's milk to lower rates of obesity, potentially because protein keeps us feeling fuller for longer and calcium can inhibit fat absorption.

But what of the eco credentials? A 2018 study found producing a glass of dairy milk results in almost three times more greenhouse gas emissions than any plant-based milk. But alternatives are hardly the epitome of environmental responsibility either – it takes around a gallon of water to grow a single almond for almond milk.

When drought hit California, where 80 per cent of the world's almonds were produced, between 2011 and 2017, progressive American magazine Mother Jones headlined an article: 'Lay Off The Almond Milk, You Ignorant Hipsters'. That, of course, was before 20 per cent of Los Angeles's hydrants ran dry last week as fires decimated the city.

Producers of coconut milk, only made in tropical climates such as in the Philippines, have been accused of exploiting workers and destroying rainforests.

So perhaps good old-fashioned cow's milk might be best after all. For now, the war of the white stuff continues – although, as with so many cultural touchpoints, what the Hollywood stars are saying may matter less than they'd like to think.