Fitness Supplements: What Works and What Doesn't
The supplement industry is worth billions, but most products don't work. Learn which supplements have real scientific backing, which are a waste of money, and how to spend less by focusing on what's proven.
The Truth About Supplements the Industry Doesn't Want You to Know
Only a handful of supplements are genuinely worth buying: creatine monohydrate, caffeine, and whey protein if you struggle to hit your protein target from food. Almost everything else on the shelf is marketing.
The supplement industry earns over 50 billion dollars a year selling promises in bottles. The marketing is aggressive, influencers push products at every turn, and the packaging promises "explosive results" and "revolutionary formulas." The reality is different: most supplements on the market have weak or zero scientific evidence that they work.
That does not mean ALL supplements are useless. A few products have a solid scientific foundation and can genuinely improve your results - but only as an addition to quality nutrition and training, never as a replacement. This guide separates the science from the marketing.
Supplements That Actually Work (Category A)
1. Creatine Monohydrate
Creatine is the most studied supplement in the history of sports science, with over 700 peer-reviewed studies behind it. It increases phosphocreatine stores in your muscles, which directly improves strength, explosiveness and high-intensity work capacity. Average strength improvement: 5-10%. Average muscle gain: 1-2 kg in the first 4-8 weeks.
The short version: take 3-5 grams of plain creatine monohydrate every day, timing does not matter, and skip the loading phase and the expensive "advanced" forms. For dosing details, side effects, myths and everything else, read our full complete guide to creatine for strength and muscle.
2. Caffeine
Caffeine improves endurance, strength and focus during training. It works by blocking adenosine receptors in the brain, reducing your perception of fatigue. Studies consistently show a 3-5% performance improvement - which translates into an extra rep or two on every set.
How to use it:
- Dose: 3-6 mg per kilogram of body weight (200-400 mg for most people)
- Timing: 30-60 minutes before training
- Source: black coffee is the cheapest option. Pre-workout supplements contain the same ingredient at a higher price
- Caution: avoid caffeine within 6+ hours of bedtime - poor sleep cancels out every benefit
3. Whey Protein
Whey protein is not magic - it is simply a concentrated protein source from milk. Its only real benefit is convenience: it is faster and easier to consume than preparing a protein-rich meal. If you already get enough protein from food (1.6-2.0 g per kg of body weight), you do not need whey. Not sure what your target should be? Our guide on how much protein you need to build muscle covers it in detail.
When it makes sense:
- You have no time for a meal after training
- You struggle to hit your daily protein target from food alone
- You are traveling and have no access to a kitchen
Supplements With Moderate Evidence (Category B)
4. Vitamin D
Most people in Europe are deficient in vitamin D, especially through the winter. Vitamin D deficiency is linked to weaker muscle function, poorer recovery and reduced testosterone. Supplementing 2000-4000 IU daily during the winter months is a sensible move for most active people.
5. Omega-3 Fatty Acids
Omega-3s (EPA and DHA) from fish oil have anti-inflammatory properties that may improve post-training recovery. A dose of 2-3 grams of combined EPA+DHA daily shows moderate benefits. If you already eat fatty fish 2-3 times per week, supplementation is probably unnecessary.
6. Magnesium
Magnesium is involved in over 300 enzymatic reactions, including muscle contraction and protein synthesis. Many active people run suboptimal levels because of losses through sweat. Supplementing 200-400 mg of magnesium glycinate or citrate can improve sleep quality and reduce muscle cramps.
Supplements That Are a Waste of Money (Category C)
7. BCAAs (Branched-Chain Amino Acids)
BCAAs were popular for years, but the science is clear: if you eat enough protein (which every active person should), BCAAs provide zero additional benefit. Whey protein already contains all the BCAAs in optimal ratios. Buying BCAAs on top of adequate protein intake is like buying bottled water when you have a tap.
8. Glutamine
Glutamine is marketed as a recovery supplement, but research consistently shows no effect on muscle regeneration or immunity in healthy people who eat normally. Your body produces plenty of glutamine on its own - supplementing does not raise it above normal levels.
9. Testosterone Boosters
Tribulus, D-aspartic acid, fenugreek - none of the popular "natural testosterone boosters" raise testosterone to a degree that would affect muscle growth. Studies show either no effect or increases so small they are clinically meaningless. Skip these products entirely and put that money into better food - the results will be indisputably better.
10. Fat Burners
Fat burners are mostly caffeine in expensive packaging, sometimes combined with ingredients that have no proven effectiveness. The only ingredient in most fat burners that actually works is caffeine - which you can get from a simple cup of coffee for a tiny fraction of the price of a box of pills.
How to Evaluate Any Supplement in 30 Seconds
New products appear every month, so it helps to have a filter. Before buying anything, run it through these questions:
- Is there human research? Rat studies and test-tube results do not count. Look for randomized controlled trials in trained humans.
- Is the effect size meaningful? "Statistically significant" can still mean practically irrelevant. A 1% improvement is not worth a monthly subscription.
- Is the dose in the product the dose in the studies? Many products include proven ingredients at a fraction of the effective dose, hidden behind a "proprietary blend" label.
- Is it third-party tested? Certifications like Informed Sport or NSF verify that what is on the label is actually in the tub - and nothing else.
- Would fixing your diet solve the same problem for free? Nine times out of ten, the answer is yes.
Your Priority List (In Order of Importance)
- 1. Creatine monohydrate: the best effect-to-cost ratio in the entire industry
- 2. Caffeine (black coffee): essentially free if you already drink coffee
- 3. Whey protein (if needed): only if you cannot reach your protein target from food
- 4. Vitamin D (in winter): roughly November through March
That short list covers everything with real evidence behind it. Everything beyond it is either a minor bonus or pure marketing.
Track Your Diet Before You Buy Supplements
Supplements are useless if your basic nutrition is off. Before spending money on any product, check whether you are eating enough protein, carbohydrates and calories for your goals. The diet tracker on Trainera.fit shows you exactly how many macronutrients you take in each day - and you will often discover the problem is not a missing supplement, but not enough protein from food.
If you want a personalized nutrition and supplementation plan, certified coaches on Trainera.fit can analyze your daily intake and recommend only what you actually need - without wasting money on products that do not work.