Supplements with the strongest evidence, and why those

If you could only take two things off the whole supplement shelf, which two? That question comes up in every gym, and the answer is shorter than most people expect. What is genuinely well researched fits into a few lines; everything else sits somewhere between “might help a little” and “sells well”.

What follows is sorted by how strong the evidence actually is: what stands firm, what looks promising but unfinished, and what gets passed around wrongly.

What we know reliably

Creatine monohydrate

The evidence here is about as consistent as sports science gets. Creatine tops up the phosphocreatine stored in muscle, which in practice means a rep or two more on sets lasting up to roughly ten seconds, slightly quicker recovery between sets, and over months a bigger gain in strength and muscle than the same training without it.

Dosing is simple: 3 to 5 grams a day, every day, training day or not. A loading phase of about 20 grams a day for five to seven days only speeds up saturation — it is optional and more likely to upset your stomach. Monohydrate is the most studied form and the cheapest one, and the pricier versions have never shown an advantage over it.

The effect is not dramatic. Realistically it is a few per cent on short, hard efforts. By supplement standards, that is a lot.

Caffeine

Second on the list for strength of evidence. It lowers how hard the effort feels, stretches out endurance, and adds a small amount of strength and power. The usual range is 3 to 6 milligrams per kilogram of body weight, taken 30 to 60 minutes before training, though people who drink it all day respond less. We covered dosing and who caffeine genuinely does not suit in a separate piece on caffeine and performance.

One cost is real. Caffeine taken after midday shortens and fragments sleep in most people, including those who insist they do not feel it. Since sleep is one of the strongest levers on recovery and growth, an evening dose often takes more than it gives.

Protein powder

Protein powder is not really a supplement — it is food in a convenient tub. The evidence is clear that total daily protein, somewhere around 1.6 to 2.2 grams per kilogram of body weight, supports muscle growth and protects muscle while you are losing fat. Evidence that the powder does something chicken, eggs, fish or beans cannot do: none.

So the question is simple. Do you hit your daily number from food? If yes, you do not need the tub. If not, one scoop is the cheapest and fastest way to close the gap.

Vitamin D, but only if you are short

This one needs precision. Topping up helps people who are deficient, and does nothing for strength or muscle mass in people whose levels are already fine. Deficiency is common through the winter, but it is confirmed by a blood test, not by how you feel, and the dose is a matter for your doctor and that test rather than a forum thread.

Probable, but not settled

The next group has decent but unfinished evidence, mostly because the benefit depends on the type of effort or shows up only in narrow conditions.

• Beta-alanine. It helps buffer acidity in the muscle, so the payoff is clearest in efforts lasting roughly one to four minutes — rowing, swimming, sets of 20 or more reps, combat sport rounds. On a set of five heavy reps it does close to nothing. It needs several weeks of daily use and often causes harmless skin tingling.
• Beetroot nitrates. They improve efficiency in endurance work in recreational athletes; in well-trained endurance athletes the effect is smaller and inconsistent. In the weights room the benefit is minor.
• Sodium bicarbonate. It works for short, very intense efforts, but it gives a lot of people serious gut trouble, which cancels out the gain in practice.
• Omega-3. There is reasonable ground for general health; specifically for muscle growth and recovery the findings are mixed and any effect is small.
• Collagen with vitamin C for tendons. An interesting idea and some of the findings are encouraging, but this is poorly settled so far and not something to build a plan around.

What they share is that none of them shifts your training outcome the way a sensible programme and enough food do.

What gets repeated wrongly

“Creatine wrecks your kidneys.” In healthy people, years of use at normal doses has not shown kidney damage. What does happen is that creatine nudges blood creatinine up, so the test result looks worse than the situation is — worth telling your doctor you take it before you give blood.

“Creatine is just water.” It is true that you hold a bit of extra water in the muscle in the first few weeks, usually one to two kilos on the scale. But the gain in strength and in muscle tissue across months of training is real and shows up separately from that water.

BCAAs and glutamine. The two most expensive habits in the gym. If your total protein intake is adequate, extra BCAAs add nothing measurable to muscle growth, and glutamine has no support for sporting goals in healthy people.

Testosterone boosters and fat burners. This is where the evidence is weakest and the promises are largest. The ingredient in those blends that actually does something is usually caffeine; most of the rest of the label is price.

Anti-inflammatory products taken after training. Large doses of antioxidants taken constantly can blunt part of the signal your body uses to adapt. On top of that, post-training soreness is not a measure of how good the session was, so switching that feeling off is not a goal worth chasing.

What this means for your training and eating

In practice the whole thing comes down to three steps. First, cover total protein and total calories. Second, if you want to, add creatine — 3 to 5 grams daily, every day, and do not expect to feel anything in the first month. Third, use caffeine deliberately, before your harder sessions, rather than as an all-day habit that eats into your sleep.

Everything above that is tuning at the margins. If the base is missing — you train irregularly, you never add weight or reps, you sleep six hours — no powder repairs that. It works the other way too: when the base is solid, a few per cent from creatine and caffeine adds up to something visible over a year.

It also helps to know what a supplement does not solve. Load selection and how close your sets come to failure matter far more, and lighter weights build muscle perfectly well when the sets are taken close enough to failure.

One adjustment goes with age: older muscle responds less to the same amount of protein, so the recommendation shifts towards the top of the range and towards larger amounts per meal. We looked at what actually changes in muscle after 60 separately.

When to see a doctor

Check before you start if you have kidney or liver disease, high blood pressure, a heart rhythm problem, if you are pregnant or breastfeeding, or if you take regular medication — caffeine and some herbal preparations interact with prescriptions. If a supplement brings on palpitations, swelling, dark urine or persistent stomach pain, stop and speak to a doctor.

In short

• Strong, consistent evidence: creatine monohydrate, caffeine, adequate total protein, vitamin D where deficiency is confirmed.
• Probably useful, but in narrow situations: beta-alanine, nitrates, bicarbonate; omega-3 more for health than for muscle.
• Weak evidence with big promises: BCAAs, glutamine, testosterone boosters, fat burners.
• Creatine: 3–5 g a day, loading optional, no harm shown in healthy kidneys.
• Caffeine: 3–6 mg/kg before training, but not in the afternoon.
• None of them makes up for irregular training, low protein or poor sleep.