Americans now spend upwards of $2 billion on protein supplements a year. Must be good stuff, right? Well, yes, if you use it right. To be sure, protein powder is a better bet than a lot of the other offerings at the Vitamin Shoppe, but magic superman potion it's not. A protein powder is simply a more convenient vehicle than whole food for delivering exactly the right amino acids at exactly the moment your body needs them to repair and add muscle fiber. In fact, one of the keys to getting the most out of your powder is timing it correctly. That's why the following primer has two parts. The first makes specific recommendations for specific times of day. And the second decodes the ingredients listed on the labels, so you'll be among the select few at your Vitamin Shoppe who actually know what they're buying.

BREAKFAST Lean Body Instant Breakfast Shake ($3/serving; labrada.com) Don't feel like eating in the morning? Go for a meal-replacement formula with a casein blend and some fat and fiber to tide you over until lunch, plus some carbs to get you going. Another good choice: Micellean Bioactive Superfood (vpxsports.com)
PRE-WORKOUT MuscleAde ($1/serving; pacifichealthlabs.com) Research suggests that a pre-workout shake may be even better than the traditional apr�s, since you'll already have the amino acids in your body as soon as you need them. Another good choice: Nitro-Tech (muscletech.com)
POST-WORKOUT Surge ($2/serving; t-nation.com) For the classic usage, you'll want a powder with all (or mostly) whey protein, maltodextrin, and minimal fat or fiber. A high-test hydrolysate product like Surge packs in extra branched-chain amino acids for good measure. Another good choice: Countdown (pacifichealthlabs.com)
SNACK Meso-Tech ($3/serving; muscletech.com) Afternoon is the time for a blend that goes heavy on casein or, like this delicious one, fiber. It tastes just like the shakes at McD's. Other choices: MET-Rx Original (metrx.com), Classic Grow! (t-nation.com), Myoplex (eas.com)

Protein Blend
Usually among the first words you'll see. Companies use the term, as opposed to just citing the various proteins individually, to get around FDA rules that require ingredients be listed in the order of quantity, which might allow something like rice oligodextrin to jump to the top of the label. The exotic names ("Metamyosyn," "AminoPlex," etc.) often given to these blends are mostly hype. Manufacturers generally buy their proteins from a small group of vendors and frequently end up using the very same stuff.

Whey
The most common powder ingredient, either inside the parentheses of a protein blend or on its own in a "100% whey" brand. It's a byproduct of cheese production that used to be thrown away but is now valued because it enters the bloodstream fast. Labels will specify either "concentrate" (the cheapest and most widely used form of whey) or "isolate" (purer, with less fat and lactose, which can upset your stomach).

Casein
Another formerly discarded cheese byproduct, but one that's prized now for the slowness with which it's digested. Because of its high cost, it's almost always found in a blend.

Milk Protein Isolates
Here's where it gets a little confusing. Supplements that list whey and/or casein separately do so with the idea of producing a more efficient muscle-building effect than what dairy provides naturally. But milk protein isolates are designed to be more like the real thing, with the same ratio of whey and casein, but with less stomach-disturbing lactose. Just to make it even more confusing, a protein blend might include whey, casein, and milk protein isolates.

Soy protein isolates
Some muscleheads are wary of soy because of its estrogenic qualities -- which could in theory limit your results in the gym and give you man boobs. But the isolate form has a fantastic mix of amino acids, including at least one thought to boost the immune system.

Maltodextrin
A cheap corn carb, it works with protein to create a surge of insulin, which helps mainline both ingredients into your muscles.

Oat Fiber
This ingredient will help thicken up your protein shake for a creamier "mouth feel" and work with casein to slow digestion when that's the goal.

Xanthan Gum
A slimy sugar used, like fiber, as a thickener.

Sunflower oil
A type of polyunsaturated fat used to add some additional thickness and flavor and slow digestion a touch more.