Whey Protein
The most studied protein supplement there is — fast-digesting, leucine-rich, and the simplest way to close a daily protein gap. Not magic; just convenient food.
Extensive randomised evidence and multiple meta-analyses: with resistance training, protein supplementation increases lean mass and strength versus training alone, with benefit plateauing around 1.6 g/kg/day total intake. Strong for satiety and appetite control. No advantage over whole-food protein when total intake is matched — the benefit is convenience and amino-acid quality, not a supplement effect.
Whey is the liquid fraction left when milk is curdled. It's roughly 20% of milk protein (casein is the rest), and it happens to have the best amino-acid profile of any common protein: high in leucine, the amino acid that flips the switch on muscle protein synthesis. That's why it dominates the literature. What the evidence actually supports is narrow but solid — combined with resistance training it increases lean mass and strength slightly more than the same calories without it, and it improves satiety. It will not build muscle on its own, and it has no advantage over meat, eggs or dairy if you're already hitting your protein target. Its real value is logistical: 25 g of high-quality protein in 30 seconds, which is the difference between hitting 1.6 g/kg and not.
- Form
- Three grades. Concentrate (~70–80% protein) is cheapest and keeps some lactose and fat — fine for most people. Isolate (≥90%) strips nearly all lactose and fat; worth it if dairy bothers you or you're counting every calorie. Hydrolysate is pre-digested for marginally faster absorption, costs much more, tastes bitter, and is rarely worth it. Look for NSF Certified for Sport or Informed Sport on the tub — third-party testing is the single most useful thing on the label, given repeated findings of heavy metals in protein powders.
- Dose
- 20–40 g per serving. The muscle-protein-synthesis response saturates around 25–40 g in most adults (roughly 2.5–3 g of leucine), so bigger scoops mostly buy you calories. What matters far more is total daily protein: about 1.6 g/kg bodyweight for most people training, up to ~2.2 g/kg when dieting or older.
- Timing
- Whenever it's convenient. The 'anabolic window' was oversold — total daily intake dominates. Practically: with or after training, or as the meal you'd otherwise skip. Spreading protein across 3–4 feedings of 25–40 g each edges out one large hit.
- Schedule
- Daily if it helps you hit your target; skip it on days you don't need it. There's no need to cycle it — it's food.
- Side effects
- Bloating, gas and loose stools, almost always from the lactose in concentrate — switch to isolate. Some people report acne flares. Nothing else at normal intakes.
- Interactions
- No meaningful drug interactions. Taken with a meal it can slightly blunt absorption of some antibiotics and levothyroxine via its calcium content — separate those by a couple of hours.
- Contraindications
- True cow's-milk protein allergy (isolate is not safe either — it's still milk protein). Significant lactose intolerance, unless you use isolate. Chronic kidney disease: high protein intakes need medical guidance, though there's no evidence that high protein harms healthy kidneys.
- Lab markers
- None routinely. If you have CKD, track eGFR and creatinine with your clinician — and note that creatinine can rise modestly from a high-protein diet or creatine use without any kidney injury, which trips people up.
- Food sources
- Milk, Greek yogurt, cottage cheese, cheese. A 200 g pot of Greek yogurt is ~20 g of protein; skimmed milk powder is the cheapest whey-plus-casein source going.
Pairs with
Creatine (the two most evidence-backed additions to resistance training; commonly taken in the same shake). Vitamin D3 and magnesium for the wider muscle-function picture. Leucine or EAAs only if you're using a lower-quality plant protein.
Where to buy
Prices are checked periodically and drift — Amazon’s is the live one. We take no commission on these links.
within Protein & meal support