Supplements: what the evidence supports, and what to skip

Guides · Nutrition

The supplement aisle is one of the loudest, most over-promised corners of fitness. Almost everything on the shelf claims to burn fat, build muscle, or boost energy — and most of it does very little. The honest, useful truth is smaller and calmer than the marketing: a short list of products has genuinely good evidence behind it, a couple more help in specific situations, and a great deal is safe to skip. This guide walks through that list plainly, so you can spend your money — if you spend it at all — on the few things that tend to earn their place.

The single most important frame to keep in mind: supplements are optional extras, not essentials. The word is literal — they supplement a diet and a training plan that are already doing the real work. No powder, capsule or scoop out-works consistent training, enough sleep, and a sensible diet built mostly from whole food. Nothing on this page is a shortcut, and none of it is required to get results. With that settled, here's what the evidence actually says.

1. The whole guide, at a glance

Here's the punchline first, because it saves you money and reading time. Supplements sort cleanly into three tiers by how strong the evidence is and how many people they actually help. Everything after this section simply explains each row in depth.

Notice what dominates the list: the things that work are cheap, boring, and few. That's the opposite of how supplements are usually sold. If you take nothing else from this page, take the table — and the reminder that a good diet and consistent training make every row here optional.

2. Creatine — the most-studied one that works

If there is a single supplement with strong, repeatedly replicated evidence for training, it's creatine monohydrate. It's also one of the most researched sports supplements in existence, which is exactly why it can be recommended calmly rather than hyped.

What it does

Your muscles use a molecule called ATP as their immediate energy currency, and for short, hard efforts they lean on a fast-recharge system built around phosphocreatine. Supplementing creatine tends to raise the amount of phosphocreatine your muscles store, which helps you regenerate ATP a little faster between hard efforts. In plain terms: it can support your ability to do slightly more high-intensity work — an extra rep or two on a heavy set, a bit more quality in repeated sprints — and it's that extra accumulated training, over weeks, that tends to translate into strength and muscle gains. Creatine doesn't build muscle directly; it helps you train a touch harder, and the training builds the muscle.

How to take it — the simple approach

This is refreshingly uncomplicated. A common, well-supported approach is a steady 3–5 g per day, every day, of plain creatine monohydrate. Take it at whatever time you'll remember — timing around your workout is a minor detail, and consistency across the week is what matters. You do not need to "load" (the higher-dose first week you'll see on labels); loading fills your muscle stores faster, but a steady daily dose gets you to the same place within a few weeks with less fuss. Monohydrate is the form with the most evidence and the lowest price — the fancier, pricier forms don't reliably out-perform it.

Is it safe?

For healthy people with healthy kidneys, creatine monohydrate has a long track record and is generally considered well tolerated at these everyday doses. The main visible effect is a small amount of water drawn into the muscle, which can nudge scale weight up a little at the start — that's intramuscular water, not fat. As always, the caveat that earns the disclaimer at the foot of this page: if you have kidney disease or another relevant medical condition, or you're pregnant or breastfeeding, clear it with a professional first.

3. Protein powder — convenience, not magic

Protein powder has good evidence behind it, but it's important to be precise about what the evidence supports. Powder isn't a special muscle-building substance. It's simply a convenient, concentrated source of dietary protein — and the benefit comes from the protein, not the powder. If your total daily protein is already where it should be from food, adding powder does little.

What protein actually does

Protein supplies the amino acids your body uses to build and repair tissue, including muscle. Eating protein — especially sources rich in the amino acid leucine — briefly raises muscle protein synthesis, the process of building new muscle protein. Paired with resistance training, adequate protein helps you build muscle when you're eating enough, and helps protect muscle when you're eating in a deficit. Whey, casein, and blended plant powders (soy, pea, rice) are all just efficient ways to deliver that protein when whole food is inconvenient.

Do you need it?

Only if you'd otherwise miss your protein target. Most people can hit their needs from food — eggs, dairy, fish, poultry, lean meat, legumes, tofu, tempeh — without any powder at all. Where a scoop genuinely helps is the practical stuff: you're busy, travelling, not very hungry after training, or you simply find it easier to close a daily gap with a shake than to cook another protein-heavy meal. That's a real, honest use case. It just isn't a requirement, and it isn't worth spending heavily on.

For how much protein to actually aim for — the evidence-based per-kilogram range, why it protects muscle in a deficit, and where the internet overstates it — see our deeper guide to protein and muscle. The one-line version: get most of your protein from food, spread across the day, and use powder only to top up if you fall short.

4. Electrolytes — situational, not daily

Electrolytes — chiefly sodium, along with potassium, magnesium and chloride — are minerals your body uses to manage fluid balance, nerve signalling and muscle contraction. You lose some of them in sweat, mostly sodium. This is where electrolyte drinks and tablets have a real, legitimate role — and also where they're wildly over-sold as an everyday health drink.

When they genuinely help

The honest rule of thumb is about duration, heat, and sweat. Electrolytes tend to matter when a session is long, hot, or leaves you visibly sweaty and salt-crusted — think an hour-plus of hard work, training in the heat, or being a naturally heavy or salty sweater. In those cases, replacing sodium (and drinking to your thirst) helps you maintain fluid balance and hold performance better than water alone. For the everyday short-to-moderate session, though, plain water is enough, and a normal diet already contains plenty of sodium.

A neat way to think about it, and one Strathlon's day-by-day view maps onto naturally, is to match your hydration approach to the kind of day you're having:

For most people, most weeks, that means electrolytes are an occasional tool for specific sessions — not a daily supplement, and certainly not a substitute for water.

5. Vitamin D — fix a deficiency, don't chase a high

Vitamin D matters for bone health, muscle function and the immune system, and your body makes it when skin is exposed to sunlight. This is the key to reading the evidence honestly: the benefit of supplementing comes almost entirely from correcting a genuine shortfall — not from pushing an already-normal level higher.

Who tends to benefit

Low vitamin D is genuinely common, and more likely if you get little sunlight (indoor lifestyle, covered skin, high latitude, winter months), have darker skin (which makes less vitamin D for a given amount of sun), are older, or spend most daylight hours indoors. For people who are actually low, supplementing to restore a healthy level is sensible and can support bone and muscle health. For people who are already sufficient, the evidence that more vitamin D adds anything — including any performance boost — is weak. The gain is in fixing the deficiency, not in exceeding it.

The sensible approach

Because it depends entirely on your own level, the accurate advice is: if you suspect you're low, the best move is to get it tested and let a professional advise a dose to correct it, rather than guessing. Vitamin D is fat-soluble, which means the body stores it and it's possible to take too much over time, so more-is-better does not apply here — a modest, appropriate dose to restore a normal level is the goal, not a mega-dose. Many people in low-sun conditions reasonably take a modest daily amount over winter; if in doubt, a test removes the guesswork.

6. What to skip for most people

Being even-handed means saying plainly what the evidence doesn't support, too. For most healthy people eating enough protein, the following are safe to skip — not because they're necessarily dangerous, but because the evidence that they help is weak, mixed, or absent, and the money is better kept.

• BCAAs (branched-chain amino acids). Marketed for muscle building and recovery, but they're just three of the amino acids you already get from any complete protein. If your total protein intake is adequate — from food or a protein supplement — separate BCAAs are largely redundant and add little for most people. Spend on hitting your protein target instead.
• "Fat-burners" and metabolism boosters. These lean heavily on marketing. Some contain stimulants that make you feel something, but there's no good evidence they meaningfully change body composition beyond what diet and activity do — and stimulant-heavy blends can carry side effects. Fat loss comes from a sustained energy deficit, not a capsule.
• "Testosterone boosters." The vast majority of over-the-counter products sold to "boost testosterone" have weak or no evidence of doing anything useful in healthy people. (Genuine clinical low testosterone is a medical issue for a doctor, not a supplement-shelf purchase.)
• Most "detox," cleanse, and exotic single-ingredient weight-loss products. Your liver and kidneys already handle detoxification; these products tend to be long on claims and short on evidence.

There's an honest nuance worth keeping: "skip for most people" isn't "useless for everyone." A clinician might recommend a specific supplement for a diagnosed deficiency — for example B12 for some people eating fully plant-based, or iron for tested low iron. Those are targeted fixes for an identified gap, decided with a professional — a very different thing from buying a general "booster" off a shelf on the promise of an edge.

7. A worked routine you can copy

To make all of this concrete, here are two simple, honest examples. They're illustrative starting points to adjust to your own body and needs — not prescriptions.

Everyday: the one-supplement routine

For most people training regularly, the entire evidence-based supplement plan can be a single line:

If your protein intake from food runs low on busy days, add a scoop of protein powder only to top up the shortfall — a convenience, not a second "must-take." That's a complete, defensible routine for a large majority of active people.

Match day / big session: electrolytes plus post-session protein

Now the situational pieces come in — but only because the day calls for them. Picture a long, hard match or a heavy training session, on a warm day, where you'll sweat a lot:

• During (long / hot / heavy-sweat): sip an electrolyte drink (mainly sodium) and drink to your thirst. This is exactly the day type where electrolytes earn their place — and it's why they're not part of your everyday routine.
• After: have a protein-containing meal or shake to support recovery — roughly a normal serving of protein (many people use something in the region of 20–40 g, but the exact number isn't critical). Whole food is perfectly good here; a shake is just handy if you're not hungry or you're still out.

And here's the reassuring part that corrects the biggest timing myth: the post-session protein window is wide, not a sprint. You don't need to slam a shake within minutes of the final whistle. Getting a solid protein meal in within a few hours — and, more importantly, hitting your total protein for the whole day — is what actually matters. The "eat-immediately-or-lose-your-gains" urgency is marketing, not physiology.

8. Takeaways, and how Strathlon fits

• Supplements are optional extras, not essentials. Diet, training and sleep do the real work. Every product here is something you can add, never something you must.
• Creatine is the standout. Well studied, cheap, and simple — 3–5 g/day of monohydrate, no loading or cycling needed, for healthy people.
• Protein powder is a convenience tool. Useful only to top up a protein target you'd otherwise miss; whole food covers most people. The deeper "how much" is in our protein and muscle guide.
• Electrolytes are situational. Reach for them on long, hot, heavy-sweat days; water is enough for everyday training.
• Vitamin D is about fixing a shortfall. Worthwhile if you're low — little sun, darker skin, winter — best guided by a test. Not a booster for the already-sufficient.
• Skip the hype tier. BCAAs (if you eat enough protein), fat-burners and "test boosters" have weak-to-no evidence for most people.

Where it's honest to say so: Strathlon doesn't sell supplements and doesn't need you to buy any. What it does do is handle the part that actually moves the needle — building your training and nutrition around your body and goals, and giving you a personalised protein target and an energy-balance view so you can see whether the fundamentals are in place. Get those right and, for most people, the supplement question shrinks to a short, cheap answer: maybe some creatine, protein powder if it's convenient, electrolytes on the hard days, and vitamin D if you're low. If you'd like the food side that all of this sits on top of, our guide to eating for results is the companion to this one.

This is general educational information, not medical or dietetic advice. Individual variation is large, and figures such as the 3–5 g/day creatine dose and the illustrative post-session protein serving are approximate, evidence-based starting points rather than exact prescriptions. Supplements can interact with medications and medical conditions, the industry is loosely regulated in many places, and "natural" does not mean proven or safe. Anyone with a health condition — including kidney disease — anyone who is pregnant or breastfeeding, anyone on medication, and anyone competing under anti-doping rules should consult a qualified physician, pharmacist or registered dietitian before adding any supplement. See our Terms for more.

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