We already know that the home environment can have a big influence on sleep quality — the presence of mold, light pollution, and noise are known to make sleep more difficult. Now it appears that using cooking oil may have a negative effect on sleep, too.
Cooking oil fumes are produced and released whenever food is fried, stir-fried, or grilled using cooking oils at high temperatures. Although our exposure to such fumes is small when cooking at home, long-term exposure can cause health problems. Studies have found that kitchen workers are more susceptible to oxidative DNA damage associated with exposure to such fumes.
A 2017 study published in the journal Environmental Pollution set out to determine whether cooking oil fumes affect sleep quality. Researchers recruited 2,197 participants with an average age of 37 years. The sleep quality of each participant was assessed using the Pittsburgh Sleep Quality Index (PSQI). Their exposure to cooking oil fumes was measured using a questionnaire on cooking habits and the cooking environment along with a urine test for the presence of urinary 1-hydroxypyrene — a biomarker of exposure to cooking oil fumes.
Researchers found that those with poor sleep quality (determined by a PSQI score greater than five) were more likely to:
- Report poor kitchen ventilation
- Preheat oil to smoking point
- Spend more than 30 minutes cooking
After further analysis, researchers found that participants who reported poor kitchen ventilation were nearly twice as likely to report sleep disturbances, while those who preheated oil to smoking point and cooked for longer than 30 minutes were approximately one-and-a-half times more likely to report sleep disturbances.
When researchers analyzed urine samples from participants, those with high levels of urinary 1-hydroxypyrene were more than twice as likely to report poor overall sleep quality.
Why do cooking oil fumes appear to harm our sleep?
The short answer is, we don’t know! More studies are needed to investigate the potential link between exposure to cooking oil fumes and sleep quality before we can definitively conclude that cooking oil fumes harm sleep.
With that being said, we do know that cooking fumes are associated with a number of health issues such as airway irritation and respiratory distress — and this may explain why sleep quality can suffer.
Are all cooking oils created equal?
In 2010, researchers compared the emissions of volatile organic compounds formed when heating coconut, safflower, canola, and extra virgin olive oils. They found that emissions drastically increased when oils began to smoke, implying that low smoke point oils may not be the best option for deep-frying. The authors found canola oil generated the lowest levels of volatile chemicals while coconut oil generated the most.
With that being said, research published in 2014 suggested that vegetable oils such as corn oil and sunflower oil emitted up to three times more aldehydes (another harmful byproduct of cooking) compared to butter — with coconut oil being found to emit the lowest amounts.
If you’re feeling confused, you aren’t alone! Although the International Agency for Research on Cancer (IARC) determined that emissions from high temperature frying are probably carcinogenic to humans, they found that neither frying method nor type of oil appeared to have a big influence on their results.
Unless you are a professional chef cooking in an unventilated kitchen, you probably don’t have much to worry about. If you’re a keen home cook, this article should simply serve as a reminder to switch on the extractor fan when you cook (research has found that an extractor fan can remove as much as 75 percent of toxic cooking fumes).
That said, this is an interesting area of research and serves as a reminder that our home environment can have just as much of an effect on sleep as our actions and behaviors.
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Martin is the creator of Insomnia Land’s free insomnia sleep training. His online course uses CBT techniques to teach participants how to sleep better without relying on sleeping pills. More than 5,000 insomniacs have completed his course and 97 percent of graduates say they would recommend it to a friend.