Why some cooking oils get toxic when heated or left in the sun
Analysis of the Generation of Harmful Aldehydes in Edible Oils During Sunlight Exposure and Deep-Frying Using High-Field Proton Nuclear Magnetic Resonance Spectroscopy
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
When oils like sunflower or sesame are fried or left in sunlight, they break down and make harmful chemicals that can hurt your body.
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
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A snapshot of a population at a single point in time. Can identify correlations and prevalence, but cannot determine the direction of cause and effect.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
When oils like sunflower or sesame are fried or left in sunlight, they break down and make harmful chemicals that can hurt your body.
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Systematic Reviews & Meta-Analyses
Max 100Randomized Controlled Trials
Max 90Cohort Studies
Max 72Case-Control Studies
Max 58Cross-Sectional Studies
Max 44Case Reports & Case Series
Max 30Expert Opinion & Narrative Reviews
Max 56 / 44
Evidence Score
A snapshot of a population at a single point in time. Can identify correlations and prevalence, but cannot determine the direction of cause and effect.
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Claims (8)
Oils with more unsaturated fats (like sunflower and sesame) break down faster and make more harmful chemicals when heated or left in the sun than oils with more saturated fats (like peanut or olive).
Whether you leave oil in the sun or fry food in it, the same bad chemicals form — just at different speeds.
Leaving cooking oils in the sun for a long time makes them break down and form harmful chemicals, especially if they’re made from seeds with lots of unsaturated fats.
Frying food in oil at high heat for an hour creates toxic chemicals in the oil, especially in sesame oil, even after just 10 minutes.
Extra virgin olive oil isn’t used for deep frying because it breaks down too easily at high heat — even experts avoid it for this reason.