Casein Protein
The slow half of milk protein — it gels in the stomach and drip-feeds amino acids for hours, which is why it's the classic pre-bed protein.
Controlled trials show pre-sleep casein (~40 g) raises overnight muscle protein synthesis and improves strength and hypertrophy over a training block versus placebo. But the comparisons that matter — casein versus simply eating the same protein earlier — show much smaller differences, and total daily protein remains the dominant variable. Solid mechanism, modest real-world edge.
Casein is about 80% of milk's protein and behaves very differently from whey: it clots in stomach acid and empties slowly, producing a low, sustained rise in blood amino acids over roughly 5–7 hours instead of whey's sharp spike. That property is the entire case for it. Pre-sleep casein (30–40 g) measurably raises overnight muscle protein synthesis and, across a training block, modestly improves muscle gains. In practice the effect is small and mostly disappears if your total daily protein is already high and well distributed — so treat it as a useful tool for people who struggle to hit their target, or who finish training late, rather than a must-have.
- Form
- Micellar casein — the intact, natural form — is what the pre-sleep research used and what you want. Calcium caseinate is processed differently, absorbs faster, and loses the point. Thickness varies a lot between brands; it will never mix like whey. Look for NSF Certified for Sport or Informed Sport.
- Dose
- 30–40 g. Pre-sleep studies use 40 g, which is on the high side; 30 g is a sensible practical dose.
- Timing
- 30–60 minutes before bed is the evidence-backed use. Otherwise, as a between-meals protein when you want something that keeps you full.
- Schedule
- Daily, or on training days only. No cycling.
- Side effects
- Bloating and a heavy, full feeling are common — it's a gel in your stomach. Lactose content is low but not zero. Some people find it disturbs sleep if taken too close to lying down.
- Interactions
- No meaningful drug interactions. Calcium content can interfere with levothyroxine and some antibiotics — separate by a couple of hours, which the bedtime timing usually handles.
- Contraindications
- Cow's-milk protein allergy. Significant lactose intolerance (though casein is lower in lactose than whey concentrate). Chronic kidney disease needs medical guidance on protein load.
- Lab markers
- None routine.
- Food sources
- Cottage cheese is the original pre-bed casein — a 200 g pot is roughly 25 g of predominantly casein protein, plus it's cheaper than the powder. Greek yogurt, milk and cheese all supply it.
Pairs with
Whey (the two are complementary — fast and slow). Creatine. Magnesium or glycine if the pre-bed serving is part of a sleep routine.
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