Taking CLA supplements for a few weeks may cause more damage to fats in your body, similar to how trans fats do, based on a chemical marker in urine.
Scientific Claim
High intake of conjugated linoleic acid (CLA) for 3 weeks increases urinary 8-iso-PGF(2α) concentration by approximately 167% compared to a control diet rich in oleic acid, indicating elevated lipid peroxidation, a marker of oxidative stress.
Original Statement
“The urine concentration of 8-iso-PGF(2α) [geometric mean (95% CI)] was greater after the ... CLA [1.2 (1.1, 1.3) nmol/mmol creatinine] ... than after the control period [0.45 (0.41, 0.50) nmol/mmol creatinine; P < 0.05].”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
RCT design with randomization and control group supports probabilistic causal language. The effect size and statistical significance (P<0.05) justify the claim with cautious wording.
More Accurate Statement
“High intake of conjugated linoleic acid (CLA) for 3 weeks is likely to increase urinary 8-iso-PGF(2α) concentration by approximately 167% compared to a control diet rich in oleic acid, indicating elevated lipid peroxidation, a marker of oxidative stress.”
Evidence from Studies
Supporting (1)
A High Intake of trans Fatty Acids Has Little Effect on Markers of Inflammation and Oxidative Stress in Humans
The study found that eating a lot of CLA for 3 weeks made a specific chemical in urine — which shows body damage from stress — go up by about 167% compared to eating olive oil-like fats, meaning CLA may cause more oxidative stress.