In the chiller aisle, the pots all look alike. Skyr, Greek yoghurt, Greek-style yoghurt, fromage frais, pots marked high protein or Icelandic style. Some are thick, some are creamy.
To know which has the most protein, you only need to understand what the maker did to the milk, and read one line on the label.
The same milk, strained more or less
It all starts as milk fermented by bacteria that thicken and sour it. To make a thicker product, you strain it. The whey drains off, once through a cloth bag, now often in a centrifuge. For 1 kg of strained Greek yoghurt, 2 to 3 kg of whey are left behind (Karastamatis et al., 2022).
That whey carries away mostly water and lactose, the sugar in milk, with less than 0.7% protein. The protein stays in the pot and becomes more concentrated. In Greece, the law requires strained cow's milk yoghurt to contain at least 5.6% protein.
Skyr comes from Iceland, where people have eaten it since Viking times. Two researchers at the University of Iceland class it as a soft cheese, curdled by acidity, sometimes with a little rennet (Gudmundsson and Kristbergsson, 2016). Cottage cheese follows the same logic, curdled milk with the whey taken off.
Why Greek-style yoghurt often disappoints
In my guides I give simple markers. A Greek-style yoghurt provides about 120 calories and 5 g of protein per 100 g. Skyr provides about 60, for 10 g of protein. For the same portion, skyr gives you twice the protein for half the calories.
With 5 g of protein for 120 calories, most of the calories in Greek-style yoghurt come from fat. In the UK, the Court of Appeal looked at this in 2014. It upheld that "Greek yoghurt" means strained yoghurt made in Greece, and noted that products sold as "Greek style" generally get their thick texture from thickeners rather than straining (Fage v Chobani, 2014).
Even among strained products, the range is wide. According to a review cited by the Greek team, they run from 3.3 to 11% protein around the world. The word on the pot guarantees nothing.
What to read on the label
Turn the pot over. In the nutrition table, the protein line per 100 g tells you straight away what you are dealing with. Above 6 g, the product has been strained or had protein added. Below 5 g, any straining has not changed much.
Then read the ingredients. A plain skyr or yoghurt needs nothing but milk and cultures. Some Greek or high protein products reach their figure by adding milk protein instead of straining, a method described by dairy scientists (Bong and Moraru, 2014). If you see modified starch, flavourings, isolates or a long run of additives, put the pot back. Buy it plain, with as few ingredients as possible, and add your own fruit if you like.
Choosing for your goal
The right pot depends on what you are after. To lose weight, skyr gives you a lot of protein for few calories, and it keeps you full. At the University of Missouri, fifteen women ate 160-calorie afternoon yoghurts with 5, 14 or 24 g of protein. With the richest Greek yoghurt, they were less hungry and asked for dinner 178 minutes later on average, against 152 minutes with the lowest protein version (Douglas et al., 2013).
To build muscle or gain weight when your appetite is low, a fuller-fat dairy or a little cheese helps raise calories without eating more volume.
At the first meal of the day, I aim for about 30 g of protein for a woman, more like 40 to 50 g for a man, and at least 30 g at the evening meal. A 150 g pot of skyr gives about 15 g, half the target for a woman. Three eggs and 200 g of cottage cheese come to about 40 g, if dairy agrees with you. For protein just before bed, I have gone through the research in this article.
Plain yoghurt and kefir keep their place, for another reason. They are fermented foods that feed your gut bacteria.
Pick the plain pot with the highest protein line and the shortest ingredient list, whatever name is printed on it, then adjust the amount to your hunger and your goal.
This article is for information only and does not replace medical advice.