The Dangers of Cooking Oil Fumes

The Dangers of Cooking Oil Fumes

Some of the major problems of cooking foods are high or very high temperature cooking, the smoke and cooking oil fumes, and the denaturation of oils.

High Temperature Cooking

High temperature cooking has been proven to have some dangers, especially associated with the cooking method and type of foods you are using. Some potentially mutagenic/carcinogenic compounds are formed during high temperature cooking. Let’s take a look:

Cooking Smokes and Cooking Oil Fumes

• Smoke released during cooking is a major health concern mostly in developing countries. Particularly, the common usage of cookstoves that use solid fuels such as wood, crop wastes, and charcoal, release indoor smokes that cause illness.
• Cooking oil fumes (COF), produced when heating and re-heating oils at high temperatures, have been recognized as a major indoor air pollutant²¹.
• A study published in 2021 found key evidence and biomarkers of the toxicity of COF²¹.
• Both cooking smokes and COFs have been proven to increase the risk of lung cancer^21,22,23,24.
• Fumes from cooking oil (COFs) contain aldehydes, a type of chemical considered to be carcinogenic.
• Some studies show that the highest total aldehyde emissions in cooking methods are produced by deep frying, followed by pan frying then by stir frying^24,25.
• In terms of oils used, sunflower oil has a higher risk of producing more aldehydes, while oils that are low in unsaturated fat, like palm oil or rapeseed oil, as well as gentle cooking methods like stir frying, don’t tend to produce such a high quantity, or as many of the types that are thought to be harmful²⁵.
• Poor ventilation or fume extraction is one of the factors that may increase the risk of lung cancer²⁴.
• Avoid cooking fumes
• Use good ventilation or fume extractors.
• Avoid cooking with oils.

Cooking Oil Degradation

• Different cooking oils withstand varying levels of heat; however, overheating of any oil can cause cooking oil hazards.
• When overheated, oils begin to lose nutritional value and flavor, and start producing free radicals and toxic fumes (COFs).
• When exposed to heat, the degradation of cooking oils occurs, and by-products are produced (free fatty acids, secondary products of oxidation, polar compounds), some of which have adverse effects on human health²⁶.
• The major decomposition products of frying oil are non-volatile polar compounds and triacylglycerol dimers and polymers²⁶.
• Some of those polar components (in particular certain aldehydes, alkyl benzenes and other aromatic hydrocarbons) are known to have a detrimental effect on human health (linked to various forms of cancer and neurodegenerative diseases such as Alzheimer’s and Parkinson’s Disease)²⁶.
• The smoke point of an oil (temperature at which oil starts to continuously release smoke) was believed to be correlated with the safety and stability under heat, but a study published in 2018 reported different findings²⁶. This study compared ten of the most commonly used cooking oils: high quality extra virgin olive oil (EVOO), virgin olive oil (VOO), olive oil (OO), canola oil (CO), rice bran oil (RO), grapeseed oil (GO), coconut oil (CoO), high oleic peanut oil (PO), sunflower oil (SO) and avocado oil (AO). The main conclusions were:
• Smoke point does not predict an oil’s performance when heated
• Oxidative stability and UV coefficients are better predictors when combined with total level of polyunsaturated fats
• Of all the oils tested, Extra Virgin Olive Oil (EVOO) was shown to be the oil that produced the lowest level of harmful polar compounds and oxidative by-products
• EVOO’s fatty acid profile and natural antioxidant content allowed the oil to remain stable when heated (unlike oils with high levels of poly-unsaturated fats (PUFAs) which degraded more readily)
• Generation of polar compounds with temperature and time was more pronounced for refined seed oils with higher initial values of smoke point and PUFAs. Canola oil, grapeseed oil and rice bran oil, were found to be the least stable and produced the highest level of polar compounds when heated
• EVOO was demonstrated to be the most stable oil when heated, followed closely by coconut oil and other virgin oils such as avocado and high oleic acid seed oils
• In 2007, another study demonstrated that, despite the heating conditions, virgin olive oil maintained most of its minor compounds and, therefore, most of its nutritional properties²⁷.
• Research also shows that safety level, in terms of aldehydes produced, is higher in the extra virgin olive oil than in the sunflower; in fact, cytotoxic and genotoxic 4-hydroxy-(E)-2-alkenals were not detected in extra virgin olive oil, unlike in sunflower oil²⁸.

Avoid Cooking Oil Degradation

• Avoid heating oils, especially vegetable oils, refined oils and oils with high levels of poly-unsaturated fats.
• When heating oils, choose extra virgin or virgin olive oil, coconut oil or avocado oil.

CONCLUSION: Eat mostly raw foods!

If you do need or want to cook, use the safest cooking methods

• The best technique to retain vitamins and nutrients is to use short cooking times and use as little liquid as possible (e.g., steaming).
• Both boiling and steaming seem to be the safest cooking methods in terms of carcinogen levels.

References

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