The US’s Food and Drug Administration describes it as a granular protein precipitate that comes from skimmed milk. It’s said to help fortify certain muscles in the chest, legs and shoulders. Unlike whey, the other dairy protein, the one that gives a sudden protein hit, casein has a slow absorption rare in the gut, meaning it releases smaller amounts of amino acids – the acids your body needs to repair itself – over a longer period of time. It’s that stuff that gym fans knock back just before bed, to aid their muscle recovery (and, it’s assumed, to make them a big bigger in turn). It’s casein.
You need it – around 0.8g per kilogram of body weight on a daily basis, which typically you’ll get from a balanced diet. But it’s recommended that athletes pump that up to between 1.2 and 1.7g per kilo of body weight, which necessitates a supplement. And around the same if you’re into endurance or strength training. But, whether you’re looking to build up or slim down – and casein is used for both – do you really need this extra? After all, the FDA – and the same is true of many national food monitoring organisations outside of the US – might describe what it is, but it doesn’t tell you whether it really works. It’s up to manufacturers to ensure the lack of impurities, for example, and that labelling is accurate. The fact is that, if a company selling a sports supplement of this kind – however popular – touts itself has having zero side-effects, it’s probably lying.
What has scientific study actually discovered, if not absolutely conclusively? For one, casein has been found to help satiety, so you feel fuller longer. For another, one study – with a small sample size of 36 subjects strength training – found that the group consuming whey and casein did outperform those on whey and glutamine; it’s assumed because it keeps your body firing on all cylinders all night, preventing it entering starvation mode and starting to break down muscle tissue. Casein also fires up your metabolism, which makes for a more effective fat burn – good to those trying to lose weight.
So, assuming you buy into its effectiveness, what type of casein product should you actually then buy? First off, go for a supplement containing hydrolyzed casein, which is the least adulterated and required the least processing. If you’re aiming to lose weight, avoid those that have too many calories per serving – a serving offering somewhere between 23 and 29g of total protein should have no more than 100 to 140 calories in it (you’ll actually need extra calories if you’re looking to build muscle). And you want a casein powder that’s highly soluble – because some of them just clump up inside the water or milk you mix it into and are really not pleasant to consume.
But while it seems to be some kind of dream scenario – this all happens while you sleep – keep in mind you might not have to consume a casein supplement at all. You could just boost certain areas of your diet – more cottage cheese, more Greek yoghurt, among the foods that stand out on the dairy aisle as being especially high in casein. And when you consider the possible side-effects of casein supplements – bloating and a disrupted immune system, for example – that’s not a bad option at all.