Core Labs Therma Lean 60 caps

3,5-Diiodo-L-thyronine (T2) and other thyroid compounds

3,5-Diiodo-L-thyronine (T2) is a thyroid hormone metabolite. Thyroid hormones raise metabolic rate and are prescription medicines.

Higenamine

Higenamine is a plant alkaloid that stimulates β2-adrenergic receptors, the same receptor family targeted by asthma bronchodilators. It is found in plants such as Nandina domestica¹.

Yohimbine (yohimbe bark, rauwolscine)

Yohimbine is an alkaloid from the bark of the African tree Pausinystalia yohimbe. It blocks α2-adrenergic receptors, which increases noradrenaline release. Rauwolscine (alpha-yohimbine) is a closely related alkaloid.

Synephrine (bitter orange, Citrus aurantium)

p-Synephrine is the main protoalkaloid of bitter orange (Citrus aurantium). It is structurally related to adrenaline and is used in weight-loss and pre-workout products².

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.

Hordenine

Hordenine (N,N-dimethyltyramine) is a phenethylamine alkaloid found in barley and beer. It acts on the dopamine D2 receptor and is marketed in pre-workout and fat-burning products⁴.

Mucuna pruriens (velvet bean, L-DOPA)

Mucuna pruriens seeds naturally contain L-DOPA (levodopa), the precursor of dopamine and the main medicine for Parkinson's disease.

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 adults⁵. Supplements supply it as choline bitartrate, alpha-GPC or citicoline.

Capsaicin (cayenne pepper, capsinoids)

Capsaicin is the pungent compound in chilli and cayenne pepper; capsinoids are milder relatives.

Green tea extract (catechins, EGCG)

Green tea extracts are concentrated sources of catechins, mainly epigallocatechin gallate (EGCG), and usually contain caffeine.

Grape seed extract (OPC)

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

Resveratrol

Resveratrol is a polyphenol found in grape skins and Japanese knotweed (Polygonum cuspidatum).

3,5-Diiodo-L-thyronine (T2) and other thyroid compounds

Analyses of US supplements found thyroid hormone compounds, including T2, in products labelled as plant extracts or vitamins, at up to 740 µg a day of 3,5-T2⁶. No controlled trials support their safety for weight loss.

Higenamine

There are no controlled human trials showing that higenamine improves exercise performance or weight loss. Analyses of US supplements found up to about 62 mg per serving, with labels that often did not state the amount¹.

Yohimbine (yohimbe bark, rauwolscine)

A small trial in professional soccer players found reduced body fat with yohimbine but no change in body mass, muscle mass or performance⁷. Larger, independent trials are lacking.

Synephrine (bitter orange, Citrus aurantium)

A review of human clinical studies reported small increases in energy expenditure and modest weight loss with bitter orange extract or p-synephrine products over 6–12 weeks, many in combination with other ingredients².

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.

Hordenine

There are no controlled human trials of hordenine for exercise performance or weight loss. Human research concerns its absorption from beer, where plasma levels were too low for a direct effect on dopamine receptors⁴.

Mucuna pruriens (velvet bean, L-DOPA)

A 12-month randomised trial in untreated Parkinson's disease in sub-Saharan Africa found Mucuna pruriens could be a cost-effective alternative where commercial levodopa is not available⁸. There is no good evidence that it raises testosterone or improves mood 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 choline⁹. Claims that choline improves focus or exercise performance are not authorised.

Capsaicin (cayenne pepper, capsinoids)

A meta-analysis in healthy adults found moderate increases in resting metabolic rate and fat oxidation with capsaicinoids or capsinoids, and called for higher-quality studies¹⁰.

Green tea extract (catechins, EGCG)

Evidence for weight loss from green tea extracts is limited and effects are small; no health claim is authorised⁹.

Grape seed extract (OPC)

A meta-analysis of 16 randomised controlled trials examined the effect of grape seed extract on blood pressure¹¹.

Resveratrol

An umbrella review of meta-analyses found high-certainty evidence that resveratrol reduced waist circumference, lowered blood pressure in people with type 2 diabetes and reduced total cholesterol in overweight adults¹².

3,5-Diiodo-L-thyronine (T2) and other thyroid compounds

Human data are limited⁶.

Higenamine

Published research concerns supplement analysis rather than effects in humans¹.

Yohimbine (yohimbe bark, rauwolscine)

Evidence for fat loss or performance is limited to small studies. Supplement labels are often inaccurate: of 49 US yohimbine supplements tested, only 2 gave accurate information on both the quantity and the known adverse effects¹³.

Synephrine (bitter orange, Citrus aurantium)

Most studies are small, short and use multi-ingredient products, and longer studies are needed to establish efficacy and safety².

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.

Hordenine

Supplement amounts are much higher than the amounts studied from beer, and their effects have not been studied⁴.

Mucuna pruriens (velvet bean, L-DOPA)

The trial used standardised preparations under medical supervision; larger double-blind trials are needed⁸. Supplements rarely state their L-DOPA content.

Choline (choline bitartrate, alpha-GPC)

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

Capsaicin (cayenne pepper, capsinoids)

Effects are small and the studies are heterogeneous¹⁰.

Green tea extract (catechins, EGCG)

Results depend on caffeine content and extract type.

Grape seed extract (OPC)

Trials are small and use different extracts and doses¹¹.

Resveratrol

Effects are modest and differ by population and dose¹².

• Not suitable for stimulant-sensitive users or those with cardiovascular conditions.

3,5-Diiodo-L-thyronine (T2) and other thyroid compounds

Thyroid hormone activity can cause a fast heart rate, palpitations, anxiety and loss of bone and muscle, and can suppress the thyroid. People with heart disease must avoid it.

Higenamine

As a β2-agonist, higenamine may raise heart rate and cause palpitations, and its safety at supplement doses has not been established¹.

Yohimbine (yohimbe bark, rauwolscine)

A review of poison-centre cases found that adverse events with yohimbine products had more serious outcomes than average exposures, including rapid heart rate, anxiety, high blood pressure and agitation¹⁴. People with heart conditions, high blood pressure, anxiety disorders or taking antidepressants should not use yohimbine.

Synephrine (bitter orange, Citrus aurantium)

The reviewed studies did not report serious adverse effects at the doses tested², but combining synephrine with caffeine and other stimulants increases cardiovascular stress. People with high blood pressure, heart-rhythm disorders or taking stimulant or antidepressant medication should avoid it.

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 infant¹⁵.

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 intake¹⁵³.

Hordenine

Human safety data at supplement doses are lacking. It may interact with MAO inhibitors and other stimulants. Analyses of sports and weight-loss supplements have repeatedly found stimulants that were not declared, or quantities different from the label¹⁶¹⁷.

Mucuna pruriens (velvet bean, L-DOPA)

L-DOPA can cause nausea, low blood pressure, involuntary movements and psychiatric effects, and it interacts with MAO inhibitors, antipsychotics and Parkinson's medicines. People with heart disease, psychiatric conditions or melanoma history should not use it without medical advice.

Choline (choline bitartrate, alpha-GPC)

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

Capsaicin (cayenne pepper, capsinoids)

Can cause stomach irritation and heartburn.

Green tea extract (catechins, EGCG)

EFSA concluded that intakes of 800 mg EGCG a day or more, taken as a food supplement, significantly increased liver transaminases, a sign of liver stress¹⁸. Green tea extracts have been linked to liver injury; take them with food and do not exceed the label serving.

Grape seed extract (OPC)

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

Resveratrol

Generally well tolerated; high doses can cause digestive upset and may interact with blood thinners.

Contains 3,5-diiodo-L-thyronine (T2), a thyroid hormone metabolite that is not authorised as food (novel food) in the EU. Contains higenamine and/or octopamine, which are on the WADA Prohibited List. Contains yohimbine. Isolated yohimbine is classified as a medicinal substance in several EU member states; its legal status depends on the country of sale.

3,5-Diiodo-L-thyronine (T2) and other thyroid compounds

Thyroid hormones and their analogues are medicinal substances and are not permitted in food supplements in the EU¹⁹.

Higenamine

Higenamine is not an authorised food supplement ingredient in the EU²⁰ and is prohibited at all times by the World Anti-Doping Agency as a β2-agonist¹⁷²¹.

Yohimbine (yohimbe bark, rauwolscine)

Yohimbine is a pharmacologically active substance. Its use in food is regulated under Regulation (EC) No 1925/2006 and national rules²², and several EU Member States treat it as a medicinal substance¹⁹.

Synephrine (bitter orange, Citrus aurantium)

Bitter orange extracts are used in EU food supplements under national rules, which differ between Member States²³.

Caffeine

Caffeine is permitted in EU foods and food supplements, subject to labelling rules. It is not on the World Anti-Doping Agency Prohibited List²¹.

Hordenine

Hordenine is not an authorised food supplement ingredient in the EU; its status depends on novel food rules²⁰.

Mucuna pruriens (velvet bean, L-DOPA)

Because it contains levodopa, a medicinal substance, the classification of Mucuna pruriens products differs between EU Member States¹⁹. No health claim for this ingredient is authorised in the EU⁹; botanical ingredients are sold under national food-supplement rules²³.

Choline (choline bitartrate, alpha-GPC)

Choline is a permitted nutrient source in EU food supplements²³⁹.

Capsaicin (cayenne pepper, capsinoids)

No health claim for this ingredient is authorised in the EU⁹; it is sold under national food-supplement rules²³.

Green tea extract (catechins, EGCG)

The EU restricts green tea extracts containing EGCG in foods under Regulation (EC) No 1925/2006 on the addition of other substances to foods²²¹⁸. No health claim for this ingredient is authorised in the EU⁹; it is sold under national food-supplement rules²³.

Grape seed extract (OPC)

No health claim for this ingredient is authorised in the EU⁹; it is sold under national food-supplement rules²³.

Resveratrol

Trans-resveratrol is authorised as a novel food in the EU under specific conditions²⁰. No health claim for this ingredient is authorised in the EU⁹; it is sold under national food-supplement rules²³.