First things first: no supplement will do for you what training, food and rest don't. If those three are off, it doesn't matter what you take. If they're on point, supplements can give you a small extra. Nothing more.
That said, some of them do have good evidence behind them. Here's what each one does.
Creatine
What it does: helps you perform better in short, intense efforts, like a set of strength work. Over time, that adds up to a bit more strength and muscle.
How to take it: creatine monohydrate, 3–5 g a day, every day, whenever you like. No loading phase needed.
Heads-up: you may gain a kilo or two at first because your muscles hold more water. It isn't fat.
It's the most studied supplement and the one I recommend most if you want to take one.
Protein powder
What it does: nothing food doesn't. It's protein, the same as in chicken or eggs, just more convenient.
Who it helps: people who don't reach their daily protein through food. For building muscle, a common reference is 1.6 to 2.2 g per kilo of bodyweight per day.
If you already get there with food, you don't need it.
Caffeine
What it does: more alertness, less feeling of fatigue and a bit more performance.
How to take it: 30 to 60 minutes before training. A coffee already gives you caffeine; you don't need a "pre-workout".
Heads-up: if you train in the afternoon or evening, it can cost you sleep. And bad sleep takes away more than caffeine gives you.
Vitamin D
What it does: it matters for your bones, your muscles and your immune system.
Who it helps: people who are deficient, which you find out with a blood test. If yours comes back low, your doctor will tell you how much to take.
Omega-3
What it does: it has benefits for general health. Its effect on strength is small.
Who it helps: people who eat little oily fish.
Beta-alanine
What it does: it can help in efforts lasting 1 to 4 minutes. For short strength sets it adds little.
Heads-up: it causes a harmless tingling on the skin.
The ones you can skip
- BCAAs: if you eat enough protein, they add nothing.
- Fat burners: what works in them is usually the caffeine, at a premium price.
- Testosterone "boosters": they don't do what they promise.
- Pre-workouts with odd blends: almost all of their effect comes from caffeine.
If you compete
Powerlifting has drug testing, and some supplements can be contaminated with banned substances. Choose brands with third-party testing, such as Informed Sport.
Before you take anything
If you take medication, have a health condition (kidney or heart disease, for example) or are under 18, check with your doctor first.
The right order
- Train with a plan and be consistent.
- Eat enough, with enough protein.
- Sleep 7–9 hours.
- Then, if you want, creatine.
If you'd like help with the first three, which are the ones that really make the difference, start here.