Supplements to gain muscle: which ones actually work according to science

Published on 1 June 2026

The supplement industry moves billions promising results that science does not support. Here is the honest list of what works, what does not, and why.

The market versus the science

The global sports supplement market exceeds 50 billion dollars a year. Most products are sold with aggressive marketing and studies funded by the industry itself. A rigorous analysis of independent evidence considerably shortens the list of supplements with proven efficacy.

Tier A - Solid evidence, use with confidence

Creatine monohydrate: The most scientifically supported sports supplement. It increases muscle phosphocreatine stores, improves performance in high-intensity efforts (6-30 seconds) and produces additional muscle gain in the long term. Dose: 3-5 g a day with no need for a loading phase. Monohydrate is as effective as more expensive forms (HCl, ethyl ester). Around 20-30% of people are genetic "non-responders".

Protein powder (whey, casein, plant-based): Convenient for reaching daily protein targets (1.6-2.2 g/kg). It has no magic properties compared with food sources: it is simply powdered protein. Whey has the best essential amino acid profile and the fastest absorption. Plant protein (pea + rice) matches it with sufficient quantity. Not necessary if you meet your targets with food.

Caffeine: Improves performance in strength, endurance and power. Reduces the perception of fatigue. Effective dose: 3-6 mg/kg of body weight. Mechanism: blocking adenosine receptors. Tolerance develops with daily use, so strategic pre-workout use (not daily) maximises the ergogenic effect.

Tier B - Marginal or context-dependent benefit

Beta-alanine: Delays fatigue in exercises lasting 1-4 minutes by buffering H+ ions. Useful for high-intensity endurance sports (CrossFit, HIIT). For standard strength training the benefit is limited. The skin tingling (paraesthesia) is harmless but annoying. Dose: 3.2-6.4 g a day in divided doses.

Second-line supplements: moderate evidence

Beyond the essentials (creatine, whey protein, caffeine, and HMB under specific conditions), there is a second category of supplements with enough evidence to justify their use in certain contexts:

Beta-Alanine: The compound that forms muscle carnosine. Carnosine acts as a lactic acid buffer during high-intensity exercise lasting 1-4 minutes. Effective dose: 3.2-6.4 g a day in divided doses (the tingling is a harmless side effect, not a problem). The main benefit is in muscular endurance activities or metabolic circuits; minimal effect in pure strength work.

Citrulline malate: Unlike oral arginine (which is poorly absorbed), citrulline malate does raise plasma arginine levels and muscle nitric oxide. It improves blood flow and fatigue tolerance. Dose: 6-8 g, 30-60 minutes pre-workout. The evidence indicates modest improvements in rep volume during high-intensity sets.

Ashwagandha (KSM-66): The most studied adaptogen. Several clinical trials show improvements in testosterone (8-15% over baseline), reduced cortisol and slight improvements in maximum strength. The effect is real but modest. Dose: 300-600 mg a day of KSM-66 extract. The main benefit is in stress management and recovery during high-load periods; it is not a dramatic testosterone booster.

Completely useless or potentially harmful supplements

CLA (conjugated linoleic acid): Decades of intense marketing, consistently disappointing evidence in humans. Mouse studies showed anti-obesity effects that do not replicate in people. It is not worth what it costs.

Collagen for muscle: Collagen is a protein low in leucine and essentially useless for muscle protein synthesis. Its use is justified for tendon and cartilage health, not for hypertrophy.

Pre-workouts with "proprietary blends": "Proprietary blends" are a marketing tactic for hiding the fact that the active ingredients (creatine, citrulline, beta-alanine) are underdosed. Buy the active ingredients separately and mix your own pre-workout: cheaper, more effective and without the unnecessary fillers.

The correct order of priority

Before investing in supplements, secure these basics: 7-9 hours of quality sleep, 1.6-2.2 g/kg of daily protein from whole foods, at least 80% training adherence, and a caloric deficit or surplus matched to your goal. Supplements in a context of poor nutrition and sleep produce marginal benefits. Creatine does not make up for sleeping 5 hours.

Supplementation protocol by goal

To maximise hypertrophy (muscle gain):
- Creatine monohydrate: 3-5 g a day, at any time
- Whey protein (if you do not reach your daily intake through food): 25-40 g post-workout
- Caffeine (pre-workout): 3-5 mg/kg, 30-45 min before
- Beta-alanine (if there is high-rep work): 3.2 g a day in divided doses

For fat loss without losing muscle:
- Creatine monohydrate (maintains strength during a deficit): 3-5 g a day
- Extra protein (target 2.2-2.8 g/kg): whey or casein depending on time of day
- Caffeine (thermogenic effect plus performance): 200-400 mg a day
- L-carnitine (modest effects on fat mobilisation with exercise): 2 g a day, taken before cardio

For strength performance (powerlifting, weightlifting):
- Creatine monohydrate: optional loading (20 g a day × 5-7 days), then 3-5 g maintenance
- Caffeine: 3-6 mg/kg before competition or a quality session
- Beta-alanine (if there is repeated high-intensity work): 4-6 g a day

What you will spend versus what you will get: supplement ROI

To help you prioritise, this return-on-investment analysis:

Creatine monohydrate: ~15-20€ a month. Effect: +5-15% in strength performance, +1-2 kg of muscle mass in 8 weeks. ROI: very high. It is the most cost-effective supplement available.

Protein powder: ~25-35€ a month (1 kg of whey). Effect: makes it easier to reach protein targets. ROI: high if the alternative is missing your daily targets. Low if you already meet them through food.

Caffeine (tablets, not speciality coffee): ~3-5€ a month. Effect: +3-4% strength performance, -5-10% in perceived fatigue. ROI: extremely high. The supplement with the best price-to-effect ratio on the market.

Beta-alanine: ~10-15€ a month. Effect: useful if you do a lot of high-rep work (15-25 reps) or circuit training. Irrelevant for pure strength. ROI: medium-low for most people.

Branded pre-workouts: ~40-70€ a month. They are usually a combination of caffeine, creatine and beta-alanine with premium marketing and underdosing. ROI: low compared with buying the components separately.

The supplement with the most impact: consistency

Consistency. The athlete who trains 3-4 days a week for 3 years straight, eats enough protein and sleeps well will usually beat the one hunting for the perfect supplement but not maintaining the training. Supplements optimise a marginal percentage of the total result. Consistent work determines 90%. Protein powder does not make up for eating 100 g of protein a day when you need 180 g.

The minimum effective supplementation protocol

If you could only pick three supplements: creatine monohydrate (3-5 g a day), protein powder to cover the dietary protein shortfall, and pre-workout caffeine. These three have the best evidence-to-cost ratio on the market. Everything else is optional. If you want to add a fourth, consider omega-3 (3 g a day EPA+DHA) for its anti-inflammatory properties and its impact on recovery. You need nothing more to maximise hypertrophy naturally and sustainably in the long term.

Where to buy supplements: a practical guide

For creatine: look for pure creatine monohydrate with no flavourings. White-label brands with GMP certification cost 15-20 euros per kg. Avoid advanced creatines such as kre-alkalyn or premium Creapure: generic creatine monohydrate has exactly the same proven efficacy. For whey protein: whey concentrate (70-80% protein) is enough for most people. Isolate (90%+) is useful for those who are lactose intolerant. For caffeine: anhydrous caffeine in tablets (200 mg per tablet) is the purest and cheapest form. Coffee works just as well if you consume the equivalent amount of caffeine.

How often to review your supplement stack

Supplements that work keep working over time (creatine, protein, caffeine). They do not need cycling or periodic rotation, except caffeine, where a week off every 6-8 weeks is recommended to restore sensitivity. It is still worth reviewing your stack every 6 months: are you taking something you no longer need because you meet your nutritional targets through food? Are there new supplements with solid evidence you did not know about? Is the cost-benefit still favourable for each one?

A permanent minimum effective stack: creatine 3-5 g a day. Protein powder if you do not reach 1.6 g/kg through food. Pre-workout caffeine. Vitamin D in winter or if you live at latitudes with little sunlight (low vitamin D levels are associated with worse muscle function and slower recovery). Everything else is optional and context-dependent.

Interactions between supplements: what you should know

Caffeine + creatine: it used to be thought that caffeine reduced creatine's effectiveness, but more recent studies do not confirm this negative interaction. You can take them together without a problem. Protein + creatine: no interaction. They can be taken together post-workout. Beta-alanine + citrulline + caffeine: this is the standard homemade pre-workout combination. They all reinforce each other with no documented negative interactions. Iron + calcium: there is a negative interaction here. Do not take iron and calcium supplements simultaneously; separate them by at least 2 hours.

Supplements with emerging evidence: what the future may offer

Research in sports supplementation advances constantly. These supplements have interesting preliminary evidence but still not enough for a firm recommendation: turkesterone (a plant-derived ecdysone steroid with possible anabolic effects in preliminary studies, though most of the product on the market is of low quality and concentration), ashwagandha (moderate evidence for reducing cortisol and improving recovery; it can be useful in high-stress periods), ursolic acid (a compound present in apples and medicinal plants with anabolic effects in animal studies; the evidence in humans is insufficient), L-carnitine (for muscle recovery after eccentric exercise there is promising evidence; for fat loss the evidence is weak). None of these justifies the investment until the fundamentals (creatine, protein, caffeine, sleep, training) are perfectly established.

Supplements specifically for women: are there differences?

The marketing of women's supplements ("for women" formulas, pink packaging, ingredients "special for the female metabolism") is basically empty marketing. The physiological mechanisms of hypertrophy, strength and recovery are functionally identical in men and women. The same evidence-backed supplements (creatine, protein, caffeine, omega-3) work just as well in women as in men. Doses are the same in mg/kg terms. The only relevant difference is the menstrual cycle: during the follicular phase (first half of the cycle), insulin sensitivity and recovery capacity are slightly better, which can translate into higher performance. During the luteal phase (second half), basal temperature is higher and performance in high-intensity exercise can be slightly lower. If you track your cycle, you can plan your hardest sessions during the follicular phase. No specifically female supplement changes these patterns significantly; periodising training around the cycle has more impact.

Your supplementation protocol: final summary

Maximum-evidence stack (for everyone): creatine monohydrate 3-5 g a day + protein powder if your dietary shortfall requires it + caffeine 3-6 mg/kg pre-workout. Advanced stack (optional with good evidence): beta-alanine 3.2 g a day for long sessions, omega-3 2-3 g EPA+DHA for recovery, vitamin D if there is documented deficiency. The rest is marketing. Invest the remaining budget in better food, not in Tier 3 or 4 supplements.

A final word about the market's honesty

The supplement industry generates more than 50 billion dollars a year worldwide. Exercise science, which is the tool for evaluating what works, is funded independently and its conclusions are systematically less profitable for the industry. Trust the science. Be sceptical of the marketing. Your progress does not depend on your wallet but on your consistency.

Starting point

The evidence on supplements is clear and accessible. Before buying any new supplement, look for human clinical trials with adequate methodology. If there are none, save your money. Your progress in the gym depends on variables that cannot be bought in any shop.

The official document behind beta-alanine

When a supplement appears sorted into an evidence tier, the reasonable question is who decided that. For beta-alanine the answer is specific: a panel of fourteen researchers signed the official position stand of the International Society of Sports Nutrition in 2015, led by Trexler and Smith-Ryan.

Their conclusions are more specific than what usually gets repeated. Four weeks of supplementation at 4 to 6 g daily significantly increases muscle carnosine concentration, which acts as an intracellular pH buffer — that is, it helps blunt the acidity accumulating during intense effort.

And here is the nuance that decides whether it is any use to you: the performance benefit is most pronounced in efforts lasting between one and four minutes. That leaves out most hypertrophy sets, which rarely run past a minute.

The last row settles the most common complaint. The tingling alarms plenty of people and makes them drop the supplement, when it is a known, benign effect that is avoided simply by splitting the dose.

The overall reading is what makes tier classification meaningful: beta-alanine has official backing, a described mechanism and an established dose, but its advantage concentrates in one specific type of effort. A supplement with solid evidence is not a supplement useful for everyone — it is a supplement useful for whoever does the kind of work that was studied.