Semi-skimmed dairy milk and unsweetened, calcium-fortified soya milk both come out on top for most people in the UK, but the honest answer is that “healthiest” depends on what you actually need from your milk: protein, bone-friendly calcium, fewer calories, or simply something that doesn’t upset your stomach. There’s no single winner for everyone, and the supermarket fridge now stretches from Jersey gold-top to oat, hemp and pea-based cartons, each with a different nutritional fingerprint.
Start with the basics of cow’s milk, because it’s still the benchmark plant-based drinks get measured against. Whole, semi-skimmed and skimmed milk contain almost identical amounts of protein and calcium, roughly 3.4g protein and 120mg calcium per 100ml, the real difference is fat. Whole milk sits around 68 calories per 100ml, semi-skimmed drops to about 46, and skimmed comes in near 35. That’s why the NHS Eatwell Guide suggests semi-skimmed or skimmed as the default choice for most adults, reserving whole milk mainly for children under two, who need the extra energy and fat for rapid growth (NHS guidance on milk and dairy).
Cow’s milk also delivers vitamin B12, riboflavin, and iodine, a nutrient that’s easy to overlook but genuinely important for thyroid function, and one that UK diets have traditionally relied on dairy to supply. Swap milk out entirely without checking your iodine intake elsewhere, and you could end up short. That’s a detail plant-milk marketing rarely mentions.
Key takeaways
- Most plant milks aren’t nutritionally equivalent to dairy—but one comes surprisingly close
- That ‘healthy’ oat milk might contain more sugar than you think
- One critical nutrient in cow’s milk is rarely replaced in plant-based swaps
Where plant-based milks actually stand up
Soya milk is the closest nutritional match to dairy, largely because soya beans are naturally protein-rich. Unsweetened, fortified soya typically provides around 3g protein per 100ml, similar to cow’s milk, along with added calcium, B12 and vitamin D to bring it in line with dairy’s profile. It’s the only mainstream plant milk the British Dietetic Association tends to flag as a reasonable straight swap for people avoiding dairy, precisely because the protein content holds up.
Oat milk has become the trendy choice, and it does bring genuine fibre, particularly beta-glucan, which has a modest cholesterol-lowering effect. But protein is thin, often under 1g per 100ml, and many oat drinks contain more carbohydrate than dairy milk because the oats are processed with enzymes that break starch down into sugars. Some brands add extra sugar on top. Almond milk, meanwhile, is the lightest option calorie-wise, sometimes under 25 calories per 100ml, but that’s partly because there’s barely any almond in it once you check the ingredients list; protein can be as low as 0.5g per 100ml. It’s essentially flavoured water with a fortification pack bolted on, which isn’t necessarily bad, just worth knowing.
Pea milk is the newer entrant worth watching. It manages to match dairy’s protein content, around 3g per 100ml in most versions, while remaining plant-based, which makes it a genuinely interesting option for vegans who miss the protein hit of cow’s milk. It hasn’t caught on in the way oat and almond have, possibly because of taste rather than nutrition.
The sugar and fortification traps
Reading the label matters more with plant milks than with dairy, because the category is far less standardised. “Barista” versions of oat and soya milk, designed to froth well for coffee, often contain added oils and sugars that push the calorie count above semi-skimmed dairy. A plain, unsweetened version of the same brand can look completely different nutritionally. Always check whether “unsweetened” appears on the front of the carton, because plenty of oat and almond drinks default to a sweetened recipe unless you specifically pick otherwise.
Fortification is the other detail that can’t be assumed. Unlike cow’s milk, which naturally contains calcium, iodine and B12, plant milks only offer these nutrients if manufacturers add them back in. Most major UK brands do fortify with calcium and vitamin D, following the same levels found in dairy, but iodine fortification is far less consistent, and B12 levels vary between brands. If you’ve switched to a plant milk as your main drink rather than an occasional addition to tea, it’s worth scanning the nutrition panel for these three nutrients specifically rather than assuming they’re all covered.
So what should actually go in your trolley
For most adults with no dietary restrictions, semi-skimmed cow’s milk remains a sound, unfussy choice: decent protein, reliable iodine and B12, moderate calories, and no need to check labels for fortification. If you’re avoiding dairy, unsweetened calcium-fortified soya milk is the nearest like-for-like swap, particularly if protein intake matters to you, say you’re active or trying to manage appetite. Oat milk suits people who want the fibre benefit and don’t mind the lower protein, though it’s not the best pick if you’re watching sugar intake closely. Almond milk works best as a low-calorie splash in coffee rather than a genuine milk replacement, given how little nutrition it actually carries per glass.
One practical habit worth adopting: buy the plain, unsweetened version of whatever milk you choose, and add your own sweetness if needed. It’s a small switch, but it removes the biggest hidden variable in the whole milk aisle, and it puts you back in control of what actually ends up in your cup of tea. As always, if you’re making major dietary changes, particularly around calcium or iodine intake, it’s worth a quick chat with your GP or a registered dietitian rather than guessing from a carton label.