Best Supplements for Focus and Energy: Research Roundup

What actually works for focus and energy?

Walk down any supplement aisle and you'll find dozens of products promising sharper thinking and steady energy. The marketing is confident. The evidence is often less so.

This roundup looks at what the research actually says about the most popular focus and energy supplements. We've graded each one based on the strength of the evidence behind it, and flagged where the claims run ahead of the data.

The short version: caffeine has the strongest evidence for attention, creatine is well-supported for physical performance rather than mental focus, and several other nutrients carry authorised health claims in Great Britain that are worth understanding precisely. L-theanine, despite its popularity, sits on a thinner evidence base in the sources we reviewed.

How we judged the evidence

We weighed each supplement against two standards. First, what do systematic reviews and meta-analyses say? Second, what claims are actually authorised by regulators?

For the second point, we used the Great Britain nutrition and health claims register, the official list of claims that food and supplement brands may legally use in Great Britain¹. Only authorised claims on that register may be used on products sold in Great Britain¹. That register is a useful reality check: it tells you which benefits have cleared a regulatory bar, and which have not.

It's worth noting what the register does not contain. There is no authorised claim for any supplement improving focus, concentration or attention. The authorised claims cover things like normal muscle function, normal psychological function, and the reduction of tiredness and fatigue¹. That gap between what's authorised and what's marketed is where most of the confusion lives.

Caffeine: the strongest evidence for attention

Caffeine is the most researched focus supplement by a wide margin, and the evidence is genuinely encouraging.

A 2025 systematic review and meta-analysis published in Psychopharmacology pooled 31 randomised, double-blinded, placebo-controlled trials with a total of 1,455 participants². All trials examined the acute effect of pure caffeine on behavioural tests of attention in rested, healthy adults².

The results showed small but statistically significant effects in favour of caffeine for both accuracy and reaction time². The effect sizes were modest: g = 0.27 for accuracy and g = 0.28 for reaction time². If you're unfamiliar with effect sizes, g is a standardised measure where 0.2 is generally considered small, 0.5 medium, and 0.8 large. So caffeine's attention benefits are real, but they're not dramatic. We've explained the concept in more detail in our plain guide to effect size.

The dose-response findings are the most practically useful part. Higher doses of 200 mg or more improved both reaction time and accuracy more than lower doses². But the relationship wasn't linear for everything. Reaction time kept improving as the dose increased, while accuracy followed a quadratic pattern: it improved up to a point, then declined at higher intakes². In plain terms, more caffeine keeps you faster, but there's a sweet spot for staying accurate.

The effect didn't depend on how much caffeine people habitually consumed, how complex the task was, or which attention network was being taxed². That suggests the benefit is fairly robust across different people and situations.

On safety, the US Food and Drug Administration cites 400 mg per day as an amount not generally associated with negative effects for most healthy adults³. That's roughly two to three 12-fluid-ounce cups of coffee³. The FDA notes wide variation in sensitivity and how quickly people clear caffeine from their bodies³. Toxic effects like seizures are estimated to occur with rapid consumption of around 1,200 mg³.

Evidence grade: strong. A meta-analysis of randomised controlled trials is about as good as supplement evidence gets. For context on why that matters, see our explainer on what a meta-analysis is.

Creatine: proven for physical bursts, not mental focus

Creatine is often marketed for brain power, but the strongest authorised claim is about physical performance.

The Great Britain register authorises this wording: "Creatine increases physical performance in successive bursts of short-term, high intensity exercise"¹. That claim applies to food providing a daily intake of 3 g of creatine, and it targets adults performing high-intensity exercise¹.

There's also a second authorised claim: daily creatine consumption can enhance the effect of resistance training on muscle strength in adults over the age of 55, at 3 g per day alongside resistance training at least three times per week¹.

What's missing from the register is any authorised claim about focus, attention or cognitive performance. Creatine's brain benefits are an active area of research, but they haven't cleared the regulatory bar in Great Britain in the way its physical performance claims have.

If you're interested in the cognitive side, we've broken down the statistics separately in our piece on creatine for cognitive performance.

For buying creatine, the form used in most research is plain creatine monohydrate powder, available as creatine monohydrate. If you prefer not to mix powder, creatine monohydrate capsules are an alternative. Creapure creatine monohydrate is made from a raw material produced in Germany and sold under several brands. UK sports-nutrition brands like Bulk and Myprotein also sell creatine alongside protein and other supplements.

Evidence grade for physical performance: strong. For focus specifically: limited, with no authorised claim in Great Britain.

L-theanine: popular, but the evidence base is thinner

L-theanine, an amino acid found in tea leaves, is widely sold as a calm-focus supplement, often paired with caffeine. It's available as L-theanine capsules.

Here's the honest position from the sources we were given: we don't have a systematic review or meta-analysis on L-theanine and focus to cite. The Great Britain register contains no authorised claim for L-theanine at all¹. That doesn't mean it does nothing. It means the evidence we can point to in this roundup is thinner than for caffeine or creatine.

A sensible approach is to treat L-theanine as a promising but less-established option. If you want to try it, the common pairing is with caffeine, since the two are often studied together for attention. But we can't put a number on that benefit from the provided sources, and we won't invent one.

Evidence grade for focus: limited, based on the sources reviewed.

Magnesium, vitamin D and omega-3s: authorised claims worth knowing

Several nutrients carry authorised claims in Great Britain that are relevant to energy and general function, even if none of them specifically mention focus.

Magnesium has the most directly relevant wording: "Magnesium contributes to a reduction of tiredness and fatigue"¹. It also carries claims for normal muscle function, normal psychological function, normal functioning of the nervous system, and the maintenance of normal bones¹. None of the authorised magnesium claims mentions sleep, which is worth knowing given how often magnesium is marketed for it¹.

Vitamin D carries claims for the normal function of the immune system, the maintenance of normal bones, and the maintenance of normal muscle function¹. We've covered the mental wellbeing research separately in our piece on vitamin D and mental wellbeing.

Omega-3s carry two relevant claims: EPA and DHA contribute to the normal function of the heart, and DHA contributes to the maintenance of normal brain function¹. The brain function claim is about maintenance, not enhancement. We've looked at the focus question specifically in our piece on whether omega-3 really improves focus.

Evidence grade: authorised claims exist, but none of these nutrients has an authorised claim for focus or attention.

Supplements at a glance

What the authorised claims don't tell you

The Great Britain register is a useful tool, but it has limits. A claim being absent from the register doesn't prove a supplement is useless. It means the evidence submitted didn't meet the regulator's bar for that specific wording, or that no one has applied for it.

Equally, an authorised claim is narrower than most marketing suggests. "Contributes to normal psychological function" is not the same as "improves your focus". "Maintenance of normal brain function" is not "boosts your brainpower". The wording matters, and brands are only allowed to use the authorised wording¹.

When you see a supplement described as "proven to improve focus", that language would not be permitted under the Great Britain rules unless a specific claim existed on the register. It doesn't¹.

How to choose a focus supplement

If you're deciding what to buy, here's a practical framework based on the evidence above.

For a reliable, short-term attention boost: caffeine is the best-supported option. The evidence comes from a meta-analysis of randomised controlled trials². A moderate dose appears to be the sweet spot for accuracy, while higher doses continue to help reaction time². Keep total daily intake within the 400 mg the FDA cites as generally safe for most adults³.

For physical performance during training: creatine monohydrate at 3 g per day is the evidence-backed choice, with authorised claims for short, high-intensity bursts and for strength gains in over-55s doing resistance training¹.

For general tiredness and fatigue: magnesium carries an authorised claim for reducing tiredness and fatigue¹. That's a different thing from focus, but it's relevant if low energy is your main issue.

For overall health alongside any focus goals: vitamin D and omega-3s carry authorised claims for normal immune, bone, muscle, heart and brain function¹. They're not focus supplements, but they support the systems that keep you functioning.

If you're curious about L-theanine: it's widely used and generally well-tolerated, but the evidence we can cite here is thinner than for caffeine. Treat it as an experiment rather than a sure thing.

Before starting any supplement, check with your GP or pharmacist if you take medication, are pregnant or have a health condition. That's especially important for caffeine if you're sensitive to it, since the FDA notes wide variation in how people respond³.

What to do this week

If you want to act on this without overcomplicating it:

1. Audit your caffeine intake. Count your daily milligrams for three days. If you're consistently under 400 mg and want a focus boost, a moderate caffeine dose before demanding work is the most evidence-backed move^2,3. If you're already high, adding more is unlikely to help accuracy and may hurt sleep.

2. Check your magnesium and vitamin D status. These aren't focus supplements, but deficiencies can leave you tired. The authorised claims cover tiredness and fatigue for magnesium and normal muscle and immune function for vitamin D¹. A GP can test for vitamin D if you're concerned.

3. If you train, consider creatine. Three grams a day is the dose behind the authorised performance claims¹. It's cheap, well-studied, and the form used in most research is plain creatine monohydrate.

4. Be sceptical of "focus" claims. No supplement has an authorised focus claim in Great Britain¹. When a product promises sharper thinking, ask what the claim actually says and whether it matches the authorised wording.

The honest summary: caffeine is the only supplement here with strong, direct evidence for attention. Everything else either supports physical performance, general function, or sits on a thinner evidence base than the marketing suggests.