Quick answer
Casein is the slow-digesting protein in milk: in a classic tracer study it held blood amino acids at a moderate level for hours, where whey spiked fast and dropped. Bulk Micellar Casein is the value pick, with 80g of protein per 100g in Strawberry for 71p per 25g of protein in the 2.5kg bag, checked 3 October 2026. WheyWise checked every label and price here on the brand's own site, and casein earns its place as a bedtime shake or a long gap between meals, not as a replacement for whey after training.
Casein is one of the two main proteins in milk, alongside whey, and the one that digests slowly. Most UK casein powders are micellar casein: Bulk Micellar Casein, for example, is made from ultra-filtered skimmed milk and has 80g of protein per 100g in its Strawberry flavour, checked on bulk.com on 3 October 2026.
What is casein protein?
Casein protein is the slow-release milk protein, sold as a powder for shakes that are meant to drip-feed protein over several hours. Micellar casein is the form most brands sell, and the two names mean the same protein in practice. A 30g serving of Bulk Micellar Casein gives 24g of protein, and a 30g serving of Myprotein Impact Micellar Casein gives 24g, according to their labels. Like whey, casein is a complete dairy protein, so it is vegetarian but not vegan.
Does casein really digest more slowly than whey?
Yes. In Boirie et al., 1997, healthy adults drank either casein or whey with the same amount of leucine. Whey caused a dramatic but short rise in blood amino acids, while casein gave a prolonged plateau, which the authors put down to slower stomach emptying. Whey stimulated protein synthesis more (68% against 31%), but casein cut protein breakdown by 34% and left a more positive leucine balance over the following 7 hours. Fast and slow, in other words, not better and worse.
Should you take casein before bed?
It is the one job casein has good evidence for. In Res et al., 2012, 16 young men who trained in the evening and drank 40g of casein 30 minutes before sleep had higher whole-body protein synthesis and a positive overnight protein balance, against a negative one on placebo. The ISSN protein position stand (Jäger et al., 2017) puts the pre-sleep dose at 30g to 40g of casein. If you already hit your daily protein target, a bedtime shake is a nice extra, not a necessity.
How much does casein cost in the UK?
Bulk Micellar Casein is the cheapest of these three casein powders, at 71p per 25g of protein in the 2.5kg bag at £56.99, checked 3 October 2026.
| Casein | Protein per 100g | Largest bag | Cost per 25g of protein |
|---|---|---|---|
| Bulk Micellar Casein | 80g | 2.5kg, £56.99 | 71p |
| Protein Works 100% Micellar Casein Black | 78g | 4kg, £104.99 | 84p |
| Myprotein Impact Micellar Casein | 79g | 2.7kg, £75.49 | 88p |
One-off prices before discount codes. Bulk (Strawberry, the only flavour in stock) and Myprotein checked 3 October 2026 on each brand's site; Protein Works label (Chocolate Silk) and price checked 23 September 2026 on theproteinworks.com.
Cheapest casein per gram of protein
Bulk Micellar Casein
1kg bag
The value micellar casein: the lowest cost per gram of protein of the three big UK casein powders.
or compare all UK prices →Cheapest casein per gram of protein
Bulk Micellar Casein
1kg bagPros
- + 71p per 25g of protein in the 2.5kg bag at £56.99, checked 3 October 2026
- + 80g of protein per 100g, 24g in a 30g serving
- + Listed as vegetarian and halal on bulk.com
Cons
- – Only Strawberry was in stock on bulk.com on 3 October 2026
- – Sweetened with sucralose
●Nutrition per scoop · 24g protein in 30g▼
Protein makes up 80%
of this 30g scoop · 106 kcal total
Casein suits anyone who wants a filling bedtime shake or a protein source that lasts through a long gap between meals. Skip it if you only have one shake a day: whey is cheaper and does more after training. For every casein ranked, see the best casein protein UK guide, or compare live prices on the casein price comparison.
Frequently asked questions
What is the difference between casein and micellar casein?
In practice there is none: micellar casein is the casein sold in most UK casein powders. Bulk says its Micellar Casein is made from ultra-filtered skimmed milk, and Myprotein sells Impact Micellar Casein as a slow-release milk protein. Both give 24g of protein per 30g serving on their labels, checked 3 October 2026.
Is casein better than whey?
Not overall. Whey is absorbed quickly and casein slowly. In Boirie et al., 1997, whey raised protein synthesis more after a meal, while casein cut protein breakdown by 34% and gave a more positive leucine balance over 7 hours. Use whey after training and casein when you will go hours without food, such as overnight.
Is casein protein vegetarian?
Usually, but check the label. Bulk lists its Micellar Casein as vegetarian and Myprotein lists Impact Micellar Casein as suitable for vegetarians, both checked 3 October 2026. Casein is a milk protein, so it is not vegan.