Supplements worth considering, and the very short list

Supplements are marketed as the interesting part of nutrition and they are the least important part. What follows sorts the field roughly by evidence quality.

Genuinely well supported

Creatine monohydrate. Covered in detail elsewhere. Three to five grams daily, cheap, safe for healthy people, modest but real effects on performance and muscle gain. The only supplement most lifters need to think about.

Caffeine. One of the best-evidenced ergogenic aids in existence. Improves endurance, reduces perceived effort, and has modest benefits for strength and power output.

Doses in the region of three to six milligrams per kilogram of body weight, roughly thirty to sixty minutes before training, are the usual research protocol. Individual sensitivity varies enormously, and habitual users show some tolerance.

Practical caveats: it affects sleep for far longer than people expect, given a half-life of around five hours or more. Late training plus a pre-workout is a reliable route to poor sleep, which costs more than the caffeine gained.

Protein powder. Not magic — it is food. But it is a convenient, cost-effective way to hit a protein target, and for people who struggle to eat enough protein from meals it is genuinely useful.

Vitamin D, for people who are deficient — which, in high latitudes during winter, is a substantial proportion of the population. Correcting a deficiency improves several outcomes; supplementing when already sufficient does little. Worth testing rather than guessing.

Reasonable evidence, narrower application

Beta-alanine. Buffers muscle acidity and has decent evidence for improving performance in efforts lasting roughly one to four minutes. Useful for high-rep training and certain sports; less relevant for heavy low-rep work. Requires daily loading over weeks and causes harmless tingling at higher single doses.

Sodium bicarbonate. Similar buffering mechanism, evidence for high-intensity efforts. Notorious for gastrointestinal distress, which is why it is used less than the evidence might suggest.

Nitrate, usually as beetroot juice. Evidence for endurance performance, less clear for resistance training. Modest effects, and they appear smaller in already well-trained athletes.

Omega-3 fatty acids, for people with low intake of oily fish. General health evidence is reasonable; the specific performance and muscle claims are much weaker.

Iron, for people with diagnosed deficiency, which is common in female athletes and in vegetarians. Do not supplement iron without testing — excess iron is harmful.

Weak or absent evidence

Branched-chain amino acids, for anyone consuming adequate total protein. Testosterone boosters. Most fat burners beyond the caffeine they contain. Glutamine for healthy people. Most joint supplements, where the evidence is mixed at best. Almost everything in a typical proprietary blend, where doses are undisclosed and usually below effective levels.

The contamination problem

The supplement industry is poorly regulated in most jurisdictions. Products have repeatedly been found to contain undeclared ingredients, including banned substances, and to contain substantially less of the listed active ingredient than claimed.

For anyone subject to anti-doping testing, this is not theoretical — positive tests from contaminated supplements are documented. Use products carrying third-party certification, and understand that the athlete is responsible for what is in their body regardless.

For everyone else, third-party testing is still the reasonable filter, because it is the only assurance that the product contains what it says.

Timing and stacking, briefly

Creatine has no timing requirement — daily consistency is the only variable. Caffeine does, and thirty to sixty minutes before training is the usual window. Protein powder is food and goes wherever it fits your intake.

Pre-workout blends combine caffeine with a collection of other ingredients, frequently at doses below anything shown to work, in proprietary blends that do not disclose amounts. If caffeine is what you want, caffeine is cheaper and you know the dose.

Be careful about stacking stimulants. A pre-workout plus coffee plus a fat burner is a substantial caffeine load, and the effect on sleep that night is larger than any performance benefit that afternoon.

The order of operations

Supplements are the last few percent, and they only exist as a meaningful few percent once everything else is handled.

Sleep seven to nine hours. Eat enough total energy. Hit a protein target. Train consistently with progressive overload. Manage stress.

If those five are in place, creatine and caffeine will add something small. If they are not, no supplement compensates, and the money is better spent on food.

The industry exists partly because supplements are an easier thing to buy than a change in behaviour. That is worth noticing before spending.