Cooking oils heated to very high temperatures create harmful fat compounds linked to lung damage and immune dysfunction, according to a 2026 research review. Omega-3 fats from fish and plant sources appear to offer protection against these harms by working differently in the body. Using fresh oil, avoiding reused cooking oil, and choosing lower-temperature cooking methods may help reduce exposure to these toxic compounds.
A new research review explains how certain fats in our food can either protect our bodies or cause harm, depending on how they’re processed. Scientists discovered that when oils are heated to very high temperatures—like during deep frying—they create harmful compounds that can damage our lungs, immune system, and cells. The good news is that understanding these fats helps us make better food choices. Omega-3 fats, found in fish and flaxseed, appear to have protective effects, while repeatedly heated vegetable oils may pose risks. This research could help food safety experts create better guidelines for cooking oils and help people understand why cooking method matters as much as what we eat.
Key Statistics
A 2026 research review in The International Journal of Biochemistry & Cell Biology found that repeatedly heated vegetable oils create harmful compounds called EpHOMEs from linoleic acid, which have been associated with pulmonary injury and immune dysfunction in critically ill patients.
According to Gram Research analysis of emerging evidence, omega-3-derived epoxy metabolites demonstrate protective effects by limiting abnormal blood vessel formation and tumor dissemination, contrasting sharply with the harmful effects of high-temperature-processed vegetable oils.
The 2026 review identified that dysregulated soluble epoxide hydrolase (sEH) enzyme activity converts protective fats into harmful ones, suggesting that enzyme control could be a therapeutic target for preventing damage from repeatedly heated cooking oils.
The Quick Take
- What they studied: How certain fats in food (called epoxy fatty acids) can either help or hurt our bodies, especially when oils are heated to high temperatures during cooking.
- Who participated: This was a research review that analyzed existing studies rather than testing people directly. Scientists examined evidence from multiple studies about how these fats affect human health.
- Key finding: High-temperature cooking of vegetable oils creates harmful fat compounds that can damage lung tissue and weaken immune function, while omega-3 fats from fish appear to protect against these harms.
- What it means for you: Choosing lower-temperature cooking methods and eating omega-3 rich foods may help protect your health. However, this research is still emerging, and more studies in humans are needed before making major dietary changes.
The Research Details
This was a comprehensive research review published in 2026 that examined scientific evidence about epoxy fatty acids—special types of fats that form during cooking and digestion. Instead of conducting new experiments, the researchers analyzed findings from many existing studies to understand how these fats work in our bodies.
The scientists focused on two main questions: First, how do our bodies process these fats when everything is working normally? Second, what goes wrong when our metabolism becomes unbalanced due to stress, poor diet, or aging? They looked at evidence from laboratory studies, animal research, and human health data to piece together the complete picture.
The review paid special attention to what happens when cooking oils are heated repeatedly or to very high temperatures—like in commercial deep fryers or when reusing frying oil. The researchers traced how these heated oils create specific harmful compounds and what damage they cause in our bodies.
Understanding how fats transform during cooking is important because most people don’t realize that cooking method changes the chemical structure of food. By reviewing all the available evidence together, scientists can identify patterns that individual studies might miss. This helps create better food safety guidelines and helps people make informed choices about how they prepare meals.
This is a research review, which means it summarizes existing studies rather than conducting new experiments. The strength of the conclusions depends on the quality of the studies reviewed. The research was published in a peer-reviewed scientific journal, meaning other experts checked the work. However, because this field is still developing, some findings are based on laboratory and animal studies rather than large human trials, so more research in people is needed to confirm recommendations.
What the Results Show
The research shows that epoxy fatty acids act like a two-sided coin in our bodies. When our metabolism is balanced and working properly, these fats actually protect our blood vessels and help control inflammation—which is good for us. However, when our bodies are stressed, not eating well, or aging, the balance tips the wrong way, and these same fats become harmful.
The most concerning finding involves what happens when vegetable oils are heated to very high temperatures, especially when the same oil is reused multiple times. During this process, linoleic acid (a common fat in vegetable oils) transforms into harmful compounds called EpHOMEs. According to Gram Research analysis, these toxic compounds have been linked to lung damage and weakened immune function in critically ill patients.
In contrast, omega-3 fatty acids—found in fish, walnuts, and flaxseeds—appear to work differently. When our bodies process omega-3 fats, they create compounds that actually limit tumor growth and prevent abnormal blood vessel formation. This suggests that the type of oil and how it’s processed fundamentally changes whether it helps or hurts our health.
The research identifies a specific enzyme called soluble epoxide hydrolase (sEH) as a key player. When this enzyme becomes overactive, it converts protective fats into harmful ones. This discovery suggests that controlling this enzyme’s activity might be a way to prevent the damage caused by repeatedly heated oils.
The review also found that metabolic stress—from conditions like obesity, diabetes, or critical illness—makes the harmful effects of these fats worse. When our bodies are already struggling, exposure to these toxic fat compounds causes more damage. Additionally, the research suggests that oxidative stress (an imbalance of harmful molecules in our cells) accelerates the conversion of protective fats into harmful ones. This means that antioxidant-rich foods might help protect against some of these effects.
This research builds on earlier discoveries about how cooking changes food chemistry, but it provides a more detailed explanation of exactly which fats are harmful and why. Previous studies showed that deep-fried foods were unhealthy, but this research explains the specific mechanism—the creation of these EpHOME compounds. The findings about omega-3 fats align with decades of research showing that fish consumption is associated with better health outcomes. However, this review adds new detail about how omega-3s work at the molecular level to protect against harm.
This is a review of existing research rather than a new study with human participants, so the conclusions are only as strong as the studies reviewed. Many of the most detailed findings come from laboratory experiments and animal studies, not from large human trials. The research doesn’t provide specific recommendations about safe cooking temperatures or how much heated oil exposure is dangerous. Additionally, individual responses to these fats may vary based on genetics, overall diet, and health status—factors that aren’t fully understood yet. More human studies are needed to confirm these findings and establish clear safety guidelines.
The Bottom Line
Based on this research, consider these practical steps: (1) Avoid reusing cooking oil, especially for deep frying—use fresh oil each time. (2) Choose lower-temperature cooking methods like steaming, boiling, or gentle pan-frying when possible. (3) Eat omega-3 rich foods like fatty fish (salmon, sardines), walnuts, and flaxseeds several times per week. (4) Limit consumption of commercially deep-fried foods, which are cooked at very high temperatures. These recommendations have moderate confidence because they’re based on emerging research—more human studies would strengthen the evidence.
Everyone should be aware of this research, but it’s especially important for people with lung disease, weakened immune systems, or critical illness, who appear more vulnerable to the harmful effects. People who frequently eat fried foods or work in kitchens with high-temperature cooking should pay particular attention. However, occasional consumption of fried foods is unlikely to cause harm in healthy people. Those with omega-3 deficiency or high inflammation markers may benefit most from increasing omega-3 intake.
If you change your cooking habits and increase omega-3 foods, you might notice improved energy or digestion within weeks, but the protective effects on lung and immune function likely take months to become apparent. Long-term benefits typically emerge over 3-6 months of consistent dietary changes. Don’t expect dramatic overnight changes—these are gradual, cumulative effects.
Frequently Asked Questions
Is it bad to eat fried foods?
Frequently eating fried foods cooked in repeatedly heated oil may increase exposure to harmful fat compounds linked to lung and immune damage. Occasional fried foods are unlikely to cause harm in healthy people, but limiting consumption and choosing fresh-oil cooking methods is safer based on current research.
What cooking method is healthiest?
Lower-temperature methods like steaming, boiling, and gentle pan-frying preserve beneficial fats better than high-temperature deep frying. These methods avoid creating the harmful compounds that form when oils are heated repeatedly or to very high temperatures.
Should I eat more omega-3 foods?
Research suggests omega-3 fats from fish, walnuts, and flaxseeds offer protective effects against the harmful compounds created during high-temperature cooking. Eating omega-3 rich foods several times weekly may help counteract some dietary risks from processed foods.
How many times can you reuse cooking oil?
This research suggests avoiding reusing cooking oil entirely, as repeated heating creates increasingly harmful fat compounds. Using fresh oil for each cooking session is the safest approach based on current evidence about toxic compound formation.
Can cooking oil temperature make you sick?
Very high cooking temperatures create compounds that may damage lung tissue and weaken immune function, particularly in people who are already ill or immunocompromised. Healthy people can tolerate occasional exposure, but regular consumption of high-temperature fried foods poses cumulative risks.
Want to Apply This Research?
- Track cooking methods used daily (note temperature and oil type), frequency of fried food consumption, and omega-3 rich meals eaten per week. Monitor any changes in energy levels, respiratory function, or immune health (colds/infections) over 12 weeks.
- Set a weekly goal to replace one fried food meal with a baked or steamed alternative, and add one omega-3 rich meal (like salmon or walnut salad). Use the app to log cooking methods and receive reminders to use fresh oil and lower temperatures.
- Create a 12-week tracking dashboard showing: (1) percentage of meals using low-temperature cooking, (2) omega-3 servings per week, (3) fried food frequency, and (4) subjective health markers like energy and respiratory comfort. Review monthly trends to identify patterns between dietary choices and how you feel.
This research review summarizes scientific evidence about how cooking methods affect fat chemistry and potential health impacts. It is not medical advice. Individuals with lung disease, immune disorders, or critical illness should consult their healthcare provider before making significant dietary changes. This research is based on emerging science; many findings come from laboratory and animal studies rather than large human trials. Individual responses to dietary changes vary based on genetics, overall health, and other factors. Always consult a qualified healthcare professional before making dietary changes, especially if you have existing health conditions or take medications.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.