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L-citrulline and citrulline malate

L-citrulline is an amino acid that the body converts to arginine, a precursor of nitric oxide, which widens blood vessels. Citrulline malate combines citrulline with malic acid².

Agmatine sulfate

Agmatine is formed in the body from the amino acid arginine and acts as a signalling molecule in the nervous system. It is sold as agmatine sulfate in sports and nootropic products.

Caffeine

Caffeine is a stimulant that blocks adenosine receptors in the brain, reducing perceived effort and fatigue. It is found in coffee, tea and energy drinks and is a common ingredient in pre-workout products³.

Dicaffeine malate (sold as Infinergy®) is caffeine bonded to malic acid. Its caffeine adds to the total caffeine in a product, but labels do not always state the caffeine equivalent.

L-tyrosine

L-tyrosine is an amino acid that the body uses to make the neurotransmitters dopamine and noradrenaline. It is found in protein-rich foods; N-acetyl-L-tyrosine is a related form⁴.

Phenylethylamine (PEA) and Eria jarensis

β-Phenylethylamine (PEA) is a naturally occurring trace amine with stimulant properties. "Eria jarensis" extract is marketed as a source of related phenethylamines such as N-phenethyldimethylamine. These compounds belong to a large chemical family that also includes synthetic stimulants found in supplements⁵.

Huperzine A

Huperzine A is an alkaloid from the club moss Huperzia serrata. It inhibits acetylcholinesterase, the enzyme that breaks down the neurotransmitter acetylcholine, and it has been used as a medicine for dementia in China⁶.

Choline (choline bitartrate, alpha-GPC)

Choline is an essential nutrient used to make cell membranes and the neurotransmitter acetylcholine. EFSA set an adequate intake of 400 mg a day for adults⁷. Supplements supply it as choline bitartrate, alpha-GPC or citicoline.

Taurine

Taurine is an amino sulfonic acid made by the body and found in meat and fish. It is involved in bile acid formation and cell volume regulation, and it is a common energy-drink ingredient⁸.

L-citrulline and citrulline malate

A review of human studies found that citrulline supplementation raises plasma arginine, and that several studies report improved exercise performance or recovery, but the results are inconsistent².

Agmatine sulfate

Controlled human research on agmatine for exercise performance is very limited. Published human data are mostly small studies and a long-term case report⁹.

Caffeine

The International Society of Sports Nutrition concludes that caffeine consistently improves exercise performance when consumed in doses of about 3–6 mg per kg of body mass, with benefits for muscular endurance, movement velocity, strength, sprinting, jumping and aerobic exercise³.

L-tyrosine

A review found that tyrosine may support cognitive performance in short-term stressful or cognitively demanding situations, when these neurotransmitters are temporarily depleted, but found no consistent effect on physical exercise performance⁴.

Phenylethylamine (PEA) and Eria jarensis

There are no controlled human trials showing that PEA or Eria jarensis extracts improve exercise performance or focus. Most published research concerns detection of phenethylamines in supplements and their regulatory status⁵¹⁰.

Huperzine A

A Cochrane review found some benefit on cognitive function in people with Alzheimer's disease, but only one study was of adequate quality and size, so there was inadequate evidence to recommend its use⁶. A Cochrane review in mild cognitive impairment found the evidence insufficient¹¹.

There is no good evidence that huperzine A improves focus or performance in healthy people.

Choline (choline bitartrate, alpha-GPC)

The EU authorises claims that choline contributes to normal lipid metabolism, homocysteine metabolism and liver function for foods that are a source of choline¹². Claims that choline improves focus or exercise performance are not authorised.

Taurine

There is no authorised EU health claim for taurine, and evidence that taurine on its own improves exercise performance in healthy people is limited.

L-citrulline and citrulline malate

Studies differ in dose, form (citrulline or citrulline malate, often with an unverified ratio) and exercise test, and many are small. The mechanism behind any performance effect is not established².

Agmatine sulfate

There are no large randomised trials showing a performance benefit from agmatine in healthy people. Claims of better "pump" or focus are not established.

Caffeine

Responses vary widely between people, partly because of genetics and habitual caffeine use. Many studies use pure caffeine, so results do not automatically apply to multi-ingredient products³.

L-tyrosine

Most studies are small and use single doses in laboratory settings⁴.

Phenylethylamine (PEA) and Eria jarensis

Product labels for phenethylamine ingredients are often unreliable. Supplements labelled as containing Eria jarensis that were tested were inaccurately labelled and contained high quantities of caffeine and undeclared stimulants¹³⁵.

Huperzine A

The trials are mostly small, of limited quality and in people with cognitive disease, so they do not apply to healthy users⁶¹¹.

Choline (choline bitartrate, alpha-GPC)

Evidence on cognitive or performance effects in healthy adults is limited.

Taurine

Most of the research uses taurine in combination with caffeine or other ingredients.

• Do not exceed the recommended daily dose.
• Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle.
• Keep out of the reach of young children.
• Contains caffeine (150 mg per serving). Not recommended for children, or for pregnant or breastfeeding women.

L-citrulline and citrulline malate

Citrulline is generally well tolerated in the doses studied. Digestive discomfort has been reported, and people taking blood-pressure or erectile-dysfunction medication should ask a doctor, because citrulline raises arginine and nitric oxide production².

Agmatine sulfate

A case report described 5 years of high daily agmatine intake without detected adverse effects⁹. One case report cannot establish safety for the wider population.

Caffeine

EFSA concluded that single doses of up to 200 mg, and daily intakes of up to 400 mg from all sources, do not raise safety concerns for healthy adults. For pregnant and breastfeeding women, daily intakes up to 200 mg do not raise concerns for the foetus or infant¹.

Higher intakes can cause anxiety, sleep disturbance, raised heart rate and blood pressure, and digestive upset. Combining several caffeine sources (coffee, energy drinks, pre-workouts) raises total intake¹³.

L-tyrosine

People taking MAO inhibitors or thyroid medication should not use tyrosine supplements without medical advice.

Phenylethylamine (PEA) and Eria jarensis

Stimulants of this family can raise heart rate and blood pressure. A case report linked a supplement containing the related compound β-methylphenylethylamine to a haemorrhagic stroke during exercise¹⁴. Avoid combining with other stimulants, MAO inhibitors or antidepressants.

Huperzine A

As an acetylcholinesterase inhibitor, huperzine A can cause nausea, diarrhoea, sweating and a slow heart rate, and it may interact with medicines that affect acetylcholine or heart rate. Anyone taking medication or with heart, lung or digestive conditions should ask a doctor first.

Choline (choline bitartrate, alpha-GPC)

High intakes can cause a fishy body odour, sweating and digestive upset.

Taurine

A risk assessment identified an observed safe level of 3 g a day of supplemental taurine¹⁵, and EFSA did not raise safety concerns for the amounts used in energy drinks⁸.

Sold as a food supplement. No health claims are made for this product.

L-citrulline and citrulline malate

L-citrulline is used in EU food supplements under national rules. No health claim for citrulline is authorised in the EU¹².

Agmatine sulfate

Agmatine sulfate is used in some EU food supplements under national rules. No health claim is authorised¹². Whether a product needs novel food authorisation depends on its history of use¹⁶.

Caffeine

Caffeine is permitted in EU foods and food supplements, subject to labelling rules. It is not on the World Anti-Doping Agency Prohibited List¹⁷.

L-tyrosine

Amino acids such as L-tyrosine are used in EU food supplements under national rules. No health claim is authorised¹².

Phenylethylamine (PEA) and Eria jarensis

Phenethylamine stimulants are not authorised EU food supplement ingredients, and several related compounds are on the World Anti-Doping Agency Prohibited List as stimulants¹⁷¹⁶.

Huperzine A

Huperzine A is a pharmacologically active substance. Its status as a food ingredient is not harmonised in the EU, and some Member States treat it as a medicinal substance¹⁸¹⁶.

Choline (choline bitartrate, alpha-GPC)

Choline is a permitted nutrient source in EU food supplements¹⁹¹².

Taurine

Taurine is used in EU foods and food supplements. No health claim is authorised¹².