Smart Brothers NZT King 20 caps

Flmodafinil (modafinil analogue)

Flmodafinil is a fluorinated analogue of modafinil, a prescription wakefulness drug. It is sold online as a "nootropic".

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 adults¹. Supplements supply it as choline bitartrate, alpha-GPC or citicoline.

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 form².

Rhodiola rosea

Rhodiola rosea is a plant from cold regions whose root extract (standardised to rosavins and salidroside) is marketed as an adaptogen.

Theacrine (TeaCrine®) and theobromine

Theacrine is a purine alkaloid related to caffeine, found in some tea plants; theobromine is the related methylxanthine in cocoa. Both are used in stimulant 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-carnitine (Carnipure®, ALCAR)

L-carnitine transports fatty acids into mitochondria for energy production. The body makes it, and it is found in meat. Acetyl-L-carnitine (ALCAR) is a related form.

Grape seed extract (OPC)

Grape seed extract is rich in oligomeric proanthocyanidins (OPCs), polyphenolic antioxidants.

Flmodafinil (modafinil analogue)

There are no published controlled human trials of flmodafinil. Research concerns its detection in doping control⁴.

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 choline⁵. Claims that choline improves focus or exercise performance are not authorised.

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 performance².

Rhodiola rosea

A 2025 meta-analysis concluded that Rhodiola supplementation can improve endurance performance and related biomarkers, although differences between studies call for cautious interpretation⁶.

Theacrine (TeaCrine®) and theobromine

An 8-week study of daily theacrine (TeaCrine®) up to 300 mg a day reported no safety concerns and no tolerance effect⁷. Evidence for performance benefits is limited.

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-carnitine (Carnipure®, ALCAR)

A meta-analysis in healthy people found that L-carnitine supplementation may improve some measures of physical performance, but concluded that more robust trials are needed to determine the best dose⁸.

Grape seed extract (OPC)

A meta-analysis of 16 randomised controlled trials examined the effect of grape seed extract on blood pressure⁹.

Flmodafinil (modafinil analogue)

Effects and safety are unknown.

Choline (choline bitartrate, alpha-GPC)

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

L-tyrosine

Most studies are small and use single doses in laboratory settings².

Rhodiola rosea

Studies are heterogeneous in extract and dose⁶.

Theacrine (TeaCrine®) and theobromine

Studies are few, small and often industry-funded⁷.

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-carnitine (Carnipure®, ALCAR)

The trials are heterogeneous⁸.

Grape seed extract (OPC)

Trials are small and use different extracts and doses⁹.

Flmodafinil (modafinil analogue)

As a modafinil-type stimulant it may cause insomnia, anxiety, headache and raised heart rate. Official medicines control laboratories have found illicit "smart drugs" in products sold in Europe¹⁰.

Choline (choline bitartrate, alpha-GPC)

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

L-tyrosine

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

Rhodiola rosea

Generally well tolerated; it may interact with antidepressants and blood-pressure or diabetes medicines.

Theacrine (TeaCrine®) and theobromine

Combined with caffeine and other stimulants, these compounds add to the overall stimulant load¹¹.

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 infant¹¹.

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 intake¹¹³.

L-carnitine (Carnipure®, ALCAR)

Generally well tolerated; high doses can cause digestive upset and a fishy body odour.

Grape seed extract (OPC)

Generally well tolerated; it may add to the effect of blood-thinning medicines.

Contains a synthetic research compound that is not authorised as food (novel food) or as a medicinal product in the EU. No dosing information for human use is provided.

Flmodafinil (modafinil analogue)

Modafinil-type substances are prescription medicines; flmodafinil is not an authorised medicine or food in the EU¹². Modafinil and its analogues are prohibited in competition by the World Anti-Doping Agency⁴¹³.

Choline (choline bitartrate, alpha-GPC)

Choline is a permitted nutrient source in EU food supplements¹⁴⁵.

L-tyrosine

Amino acids such as L-tyrosine are used in EU food supplements under national rules. No health claim is authorised⁵.

Rhodiola rosea

No health claim is authorised⁵.

Theacrine (TeaCrine®) and theobromine

Theacrine is not an authorised novel food in the EU¹⁵; theobromine occurs naturally in cocoa. No health claim for this ingredient is authorised in the EU⁵; botanical ingredients are sold under national food-supplement rules¹⁴.

Caffeine

Caffeine is permitted in EU foods and food supplements, subject to labelling rules. It is not on the World Anti-Doping Agency Prohibited List¹³.

L-carnitine (Carnipure®, ALCAR)

No health claim for this ingredient is authorised in the EU⁵; it is sold under national food-supplement rules¹⁴.

Grape seed extract (OPC)

No health claim for this ingredient is authorised in the EU⁵; it is sold under national food-supplement rules¹⁴.