Why swapping cow's milk for oat drinks could be bad news for your bones, teeth… and waistline

When was the last time you heard someone order a coffee with ordinary milk? These days, it’s oat, almond or another dairy-free alternative, as what was once a niche trend has become mainstream – with four in ten consumers in the UK now using dairy alternatives, according to market research company Mintel.But then last week came research, published in The Lancet Planetary Health, which warned that swapping even some of the cow’s milk, cheese or yoghurt in your diet for plant-based alternatives could leave you missing out on vital nutrients.Teenage girls and young women face the greatest risks, with the researchers, from the University of Surrey and Queen’s University Belfast, calculating that replacing just a third of dairy with plant-based alternatives could leave 65 per cent of adolescent girls missing out on iodine, a mineral essential for thyroid function.But older people – i.e. those aged over 65 – could also be at risk, with some oat milks containing 85 per cent less protein than dairy, at an age when getting enough protein is vital to prevent muscle loss – a major cause of falls, the leading cause of accidental death in this age group.Another concern is that plant-based milk can lack two key B vitamins, B2 and B12 – which are found naturally in cow’s milk.A prolonged lack of vitamin B2 can cause mouth sores and skin problems such as a red, scaly rash, while too little B12 can cause anaemia, leading to extreme tiredness and breathlessness. A milkman making a delivery in 1972. Today, cow's milk is falling in popularity with four in ten UK consumers now using dairy alternatives‘Lower food intakes [of these two B vitamins] in older people can put marginal insufficiency into deficiency,’ Mike Lean, a professor of human nutrition at the University of Glasgow, told Good Health.For the latest study, researchers examined nutritional information of 289 plant-based milks, yoghurts and cheeses sold in the UK and found that just 12 per cent contained added iodine. Fewer than half contained vitamin B12 and only one in five had vitamin B2.Professor Lean blames ‘the current craze for dairy avoidance’ on ‘a quest to reduce weight gain – and a misplaced belief that dairy products are hazardous by increasing cholesterol’.Indeed, a study involving more than 136,000 people, published in The Lancet in 2018, found that those consuming more than two portions of dairy a day had a 16 per cent lower risk of dying or suffering serious heart problems – including heart attacks and strokes – than those who consumed none.One theory is that the calcium in cheese, for instance, binds to the fat in the gut, allowing it to pass out of the body rather than being absorbed. Professor Lean adds: ‘The non-dairy industry has amplified these incorrect beliefs for commercial reasons.’And the consequences of missing out on other nutrients can be serious. Particularly worrying is that women who are pregnant or planning to have a baby don’t get enough iodine during pregnancy.‘Iodine is especially important prior to and during pregnancy,’ says Sarah Bath, an associate professor of public health nutrition at the University of Surrey and a co-author of the latest study. ‘It supports thyroid hormone production, growth and foetal brain development.’The researchers calculated that if teenage girls gave up dairy completely, 71 per cent would get too little calcium, potentially putting their future bone health at risk (most of our bone mass is built during childhood and adolescence).‘Low calcium can stunt growth in younger people and exacerbate osteoporosis in older people,’ Dr Simon Welham, a nutrition expert at the University of Nottingham, told Good Health.And don’t assume organic plant milks are healthier.‘Organic plant-based milks are the worst because they’re prohibited [under organic food regulations] from adding vitamins and minerals,’ says Tom Sanders, an emeritus professor of nutrition and dietetics at King’s College London.Given such products’ popularity, Dr Pauline Scheelbeek, an associate professor at the London School of Hygiene & Tropical Medicine, says this raises questions about whether organic rules should be changed to allow plant milks to be fortified too.Some manufacturers acknowledge the discrepancy in terms of nutrition. For instance, on Arla’s website it says: ‘You should not think of non-dairy milk alternatives as substitutes for cow’s nutrient-dense milk.’But it’s not just the nutrients that are missing. Some plant milks contain oils, emulsifiers and stabilisers to make them look and taste more like dairy.In 2025, the Government’s Scientific Advisory Committee on Nutrition warned that most plant-based milks would be classed as ultra-processed foods (UPFs). As a rough rule of thumb these contain industrially processed ingredients and additives which are not used in home cooking. A diet high in UPFs is linked to weight gain, type 2 diabetes and heart disease. And while plant milks generally have a lower environmental impact than dairy, Professor Lean warns that their green credentials are not straightforward.‘Manufacturing, packaging and transport can add greenhouse gas production,’ he says.Sugar is another concern. Some plant milks have sugar added. A study published in the British Journal of Nutrition earlier this year found that almost three in ten plant milks sold in the UK were sweetened, up from fewer than one in four in 2020.The amounts can be surprisingly high – even in those labelled as having no added sugar. One organic rice milk labelled as ‘no added sugar’ contains almost 18g in a 250ml glass. This is equivalent to eight McVitie’s digestive biscuits. New research has warned that swapping cow’s milk, cheese or yoghurt in your diet for plant-based alternatives could leave you missing out on vital nutrientsSweetened versions can contain as much as 25g, more than twice the amount in cow’s milk.Meanwhile, oat milk contains maltose, a type of sugar produced when the oats are broken down during manufacturing. This means even drinks that are labelled ‘no added sugar’ can contain sugars.Bacteria in the mouth feed on these sugars, producing acids which damage tooth enamel.The sugar in milk (lactose) is less likely to cause dental decay as it produces less acid – and because milk also contains calcium and proteins which protect teeth, says Bridget Benelam, a nutrition scientist at the British Nutrition Foundation.The Government’s Scientific Advisory Committee on Nutrition has recently warned that switching to plant-based milks could increase sugar intake across all age groups. It advised that sweetened plant milks should not be used as a replacement for cow’s milk in children aged one to five.‘It’s best to choose unsweetened plant-based drinks fortified with micronutrients including calcium, iodine and B12,’ says Bridget Benelam.It’s not just plant-based milk. Cheeses and yoghurts made with vegetable oils, starch, soya and coconut are increasingly popular, yet many contain little of the protein, calcium or other nutrients people might expect them to have.The Coconut Collab’s natural coconut yoghurt contains just 1.2g of protein per 100g, compared with roughly 4g in ordinary natural dairy yoghurt.It also contains 9g of saturated fat per 100g, compared with around 2.6g in full-fat natural dairy yoghurt – and there’s no added calcium or iodine listed on its nutritional information.Professor Sanders warns: ‘The plant alternatives are not nutritionally equivalent.’The solution would be to add the ‘missing’ nutrients. Indeed, in July last year, the Government’s scientific advisers recommended that plant-based drinks should be fortified with iodine, calcium and vitamins B2 and B12 at levels which are comparable with semi-skimmed cow’s milk.Yet while some are fortified, ‘others are not’, says Gunter Kuhnle, a professor of nutrition and food science at the University of Reading. ‘That makes it confusing for a consumer who does not want to spend ages reading food labels,’ he adds.Professor Lean believes we shouldn’t be so worried about consuming dairy. ‘Humans have used dairy products for most of our current civilisations, within most cultures for more than 9,000 years,’ he says. So what's in your oat milk? A bottle of M&S Barista Oat Drink, which due to the additives it contains, counts as an ultra-processed foodCow's milk has just one ingredient: milk. But some oat milks contain many more.Take M&S Barista Oat Drink (£2.20 for 1 litre), with its 14 ingredients: water, oats, sunflower oil, chicory fibre, broad bean protein, coconut oil, calcium phosphates, E340 (an acidity regulator), sea salt, E471 (an emulsifier), E418 (a stabiliser), iodine, vitamins B12 and D.Technically, thanks to the additives (including the added fibre), this counts as an ultra-processed food.‘Current advice is that these additives have been extensively tested for toxicology and are safe for human consumption,’ says Jules Griffin, a professor of nutrition and metabolism at the University of Aberdeen.However, he points out that studies have linked ultra-processed foods to ill health in ways that cannot be explained simply by their high levels of salt, sugar and saturated fat – additives are thought to be the key. You could make your own oat milk, which is simple and cheap (although it has little protein, and no calcium, iodine or vitamins B2 and B12).How to make itBlend 100g of porridge oats and one litre of very cold water in a food blender for 30 seconds (any longer and the mixture can become unpleasantly slimy).Strain through a fine sieve lined with muslin or a clean tea towel. Pour into a clean bottle and refrigerate for up to three days, shaking well before use.