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ESRU

Conjugated linoleic acid (CLA)

Mixture of positional and geometric linoleic acid isomers; supplement for «fat burning» and sports nutrition; not registered as a medicine by AEMPS

ATC code: A08AX-CLA

Brand names: Tonalin CLA, Clarinol CLA, Sports Research CLA, NOW CLA

Updated · Methodology

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

D

Weight loss

Not recommended

CLA is widely marketed as a «fat burner» and «lean mass» supplement. The Whigham 2007 meta-analysis in overweight adults reported an average -0.09 kg fat mass per week – clinically negligible: at 12 weeks the difference vs placebo was about 1 kg. AEMPS has not approved CLA for weight loss; rejected the corresponding health claim. Evidence-based options are caloric deficit, physical activity and GLP-1 agonists (semaglutide, liraglutide) under medical supervision when indicated. Prolonged CLA use is linked to raised insulin-resistance markers and risk of non-alcoholic fatty liver disease.

Sources

  1. AJCN: Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis (2007)
F

Anti-aging and longevity

Not recommended

Sports blogs include CLA in stacks for «lean mass», «anti-ageing» and «metabolism boost». No long-term RCTs in healthy adults with mortality or age-related disease endpoints exist. and AEMPS have not registered the substance as a geroprotector. Known risks of prolonged use are raised and insulin resistance, hepatotoxicity in predisposed individuals and increased systemic inflammation markers. Evidence-based ageing-slowing options are regular aerobic and resistance training, Mediterranean diet, smoking cessation, BP and glucose control.

Sources

  1. AJCN: Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis (2007)
How to read tiers A–F
  • AStrong evidence – first or second line in international guidelines
  • BRecommended in selected cases
  • CStudy data contradict each other
  • DBenefit not proven, no documented harm
  • FDocumented harm, or risk without benefit

Mechanism of action

Natural mixture of linoleic acid isomers with conjugated double bonds. Commercial supplements contain two main isomers, cis-9, trans-11 and trans-10, cis-12, usually 50:50 (Tonalin, Clarinol). Putative in vitro mechanisms include inhibition of lipogenesis via stearoyl-CoA desaturase, PPAR-α activation and increased adipocyte apoptosis. In humans the effects on body composition are weak and not reproducible. CLA reduces fat mass in mice; a comparable effect in humans has not been demonstrated.

Safety

Contraindications

  • Pregnancy and lactation
  • Metabolic syndrome and non-alcoholic fatty liver disease
  • Poorly controlled diabetes mellitus
  • Age under 18 years
  • Hypersensitivity to the components

Serious adverse effects

  • Raised ALT and AST; cases of drug-induced hepatitis have been reported
  • Worsened insulin resistance and risk of manifest type 2 diabetes
  • Reduced HDL cholesterol
  • Cases of non-alcoholic fatty liver disease have been reported with long-term use

Common adverse effects

  • Nausea
  • Diarrhoea and flatulence
  • Epigastric pain
  • Heartburn

Pregnancy: can you take Conjugated linoleic acid (CLA)?

Adequate safety data in pregnancy are lacking. AESAN does not recommend CLA supplements during gestation.

Breastfeeding: can you take Conjugated linoleic acid (CLA)?

No milk transfer data are available. AESAN does not recommend use during lactation.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

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Frequently asked

What is Conjugated linoleic acid (CLA) used for?

Conjugated linoleic acid (CLA) is evaluated for the following indications with varying evidence strength: Weight loss (evidence tier D), Anti-aging and longevity (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Conjugated linoleic acid (CLA)?

Common side effects of Conjugated linoleic acid (CLA) (≥ 1 in 100): Nausea, Diarrhoea and flatulence, Epigastric pain, Heartburn. See the Safety section for uncommon and serious reactions.

Is Conjugated linoleic acid (CLA) safe during pregnancy?

Adequate safety data in pregnancy are lacking. AESAN does not recommend CLA supplements during gestation.

Is Conjugated linoleic acid (CLA) compatible with breastfeeding?

No milk transfer data are available. AESAN does not recommend use during lactation.

Who should not take Conjugated linoleic acid (CLA)?

Conjugated linoleic acid (CLA) is contraindicated in: Pregnancy and lactation; Metabolic syndrome and non-alcoholic fatty liver disease; Poorly controlled diabetes mellitus; Age under 18 years; Hypersensitivity to the components. Full list in the Safety section.

Other drugs in this group

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