As a doctor and gut health expert, this is why I believe milk is for babies and NOT for grown-ups – despite what the dairy industry tries to tell us

From early childhood we’re taught that milk is essential for health.

At primary school in the 1980s, I remember the milkman arriving every day with boxes of slightly sweet, lukewarm milk, which were handed to us like little cartons of goodness.

The message was clear: drink your milk, grow up strong.

Yet as a doctor and gut health, I feel it’s time to debunk this myth. It’s time we accepted a basic truth: milk is for babies, not grown-ups.

Despite what the dairy industry tells us, it’s not essential for strong and healthy bones.

Yogurt is not the superfood it’s made out to be. And as for trendy kefir fermented milk drinks? Well, we need more studies before recommending them to everyone.

But you’re probably asking, haven’t we evolved to drink milk?

To answer this, it’s important to understand the basic biology. Human breast milk is a high-energy fuel containing a dairy sugar called lactose, which babies need for growth and development.

In the gut, lactose is broken down by an enzyme called lactase. After weaning, humans no longer depend on milk for nutrition and the body’s production of lactase starts to decline.

By adulthood, two-thirds of the world’s population no longer produce enough lactase to digest lactose comfortably. So when they drink cow’s milk, the sugars pass undigested into the colon, where bacterial fermentation can cause gas, bloating, cramping, abdominal pain and diarrhoea.

Because cow’s milk is promoted so heavily as essential to health, people who can’t tolerate it may feel there’s something wrong with them – but their inability to digest milk is actually the human default setting.

Even if you are one of the millions of people in the UK uncomfortably familiar with the symptoms of lactose intolerance, you might still be asking: isn’t milk vital for healthy bones?

On billboards, TV adverts and school campaigns, the dairy industry has long promoted the idea that calcium equals bone health, and milk equals calcium. That message but great marketing but the science is less convincing.

Milk provides calcium, which is important for bone health – but across large studies and meta-analyses, higher milk intake has not been shown to reduce the risk of fractures.

Another key point is that calcium isn’t actually made by cows. It’s a mineral in the soil, absorbed by plants, and when these are eaten by cows the calcium passes into the milk. But there are many other rich sources, such as leafy greens, kale, beans and nuts.

For healthy bones, the World Health Organisation recommends at least 500mg of calcium daily for adults. A single serving of cooked spring greens or kale can provide roughly 150mg-250mg of calcium, while pak choi, broccoli, rocket, watercress, beans, almonds and chia seeds can top up your intake.

A 100g serving of calcium-set tofu delivers 350mg-400mg of calcium, roughly the same as a 300ml glass of cow’s milk. Most plant milks these days match cow’s milk for calcium per serving.

In other words, getting enough calcium without cow’s milk is surprisingly easy.

And remember, bone health isn’t just about calcium.

Maintaining bone density also requires vitamin D, which isn’t primarily obtained from food but is produced in the skin through exposure to sunlight, or else taken as a supplement.

Another powerful tool is weight-bearing exercise.

Resistance training, brisk walking, running, dancing, climbing stairs, yoga, tennis or football all help bones keep building and remodelling, staying strong well into older age. To put it another way, bone strength isn’t found in a carton of milk – it’s built through what we eat and how we live.

Fermented dairy products such as yogurt are often easier to digest than unfermented milk, and can be a good source of protein and calcium.

But despite bright packaging and words such as ‘live cultures’, ‘probiotic’ and ‘gut health’, it isn’t a superfood. The common belief is that yogurt provides a natural boost to your microbiome, the vast ecosystem of gut bacteria that supports digestion, immune function, metabolic health and inflammation control. But, again, the science is not as convincing as the claims.

While our gut microbiome contains around 1,500 strains of bacteria, a typical yogurt contains only two to five. Yogurt is also zero fibre, so is lacking a key nutrient for your gut microbes.

People who eat yogurt regularly tend to gain less weight than those who don’t – but that may be because they also exercise more, eat more fibre and have generally healthier diets.

When tested more directly, the picture changes.

Studies in which people simply add yogurt to their diet, without cutting calories or changing other habits, show no meaningful or sustained weight loss.

So if yogurt doesn’t quite live up to the hype, what about kefir?

It can contain far more types of microbes, so it looks like the kind of gut-health fix that people have been hoping for. But the evidence isn’t there yet. While kefir can change the mix of bacteria in the gut, studies don’t consistently show that adding kefir to your diet causes clear improvements in the important results that matter in health, such as blood sugar or inflammation.

In contrast, similar studies looking at the benefits of a healthy, high-fibre, low-meat diet, with or without dairy, have shown that dramatic changes to the microbiome, plus significant improvements in cholesterol levels, fasting glucose – the amount of sugar still in your bloodstream at least eight hours after eating – and markers of chronic inflammation.

For decades, cow’s milk and dairy yogurt have been sold to us not just as foods, but as nutritional necessities. However, the evidence shows human biology doesn’t rely on breast milk or any kind beyond infancy, and most adults around the world can’t fully digest it comfortably.

Like many other foods, dairy products can provide protein and calcium, so, yes, there is space for them in a healthy diet, but they are not essential.

You can enjoy dairy milk, yoghurt and kefir as part of a healthy diet. But choosing to get none of your calories from dairy is also a perfectly valid, healthy choice. What adult humans need is a diverse, calcium-rich diet, regular exercise, vitamin D and evidence-based nutritional advice – not dairy marketing slogans dressed up as science.

What Your Doctor Isn’t Telling You About Food, by Dr Alan Desmond, is out now (Yellow Kite, £22).