Seed Oils, Industrial Processing, Hexane and AGEs: Should You Be Worried?
- Alastair Hunt
- May 3
- 4 min read
Updated: 4 days ago
Part 4 of the Seed Oils Series
Processing
One of the major concerns raised about seed oils relates to how they are processed. Unlike cold-pressed olive oil, many commercial seed oils are refined using industrial methods involving heat, chemical extraction, and deodorisation. Critics argue that these processes introduce toxins such as residual solvents (like hexane) and damage the oil’s structure, creating harmful byproducts that could promote disease.
First, the chemical extraction process often uses hexane, a petroleum-derived solvent. After extraction, the hexane is evaporated during refining, leaving behind minimal residues. Regulatory agencies such as the European Food Safety Authority (EFSA) and the United States Food and Drug Administration (FDA) have established strict limits on allowable hexane residues in food-grade oils. Analyses consistently show that residual hexane levels in bottled seed oils are extremely low, typically well below safety thresholds.
Human studies do not show any link between dietary intake of refined seed oils and hexane toxicity - there is no evidence of neurological damage from food sources which is what one would expect to see. Most toxicity concerns around hexane come from industrial exposure, where workers inhale high concentrations over long periods - a completely different scenario from trace dietary exposure.
Processing can, however, alter oils chemically. High heat, oxygen exposure and extended storage can promote the formation of lipid peroxidation products, such as aldehydes and hydroperoxides. Some aldehydes have been associated with oxidative damage in laboratory settings when present at high concentrations. Seed oils are often criticised for being prone to oxidation during manufacturing, however, these concerns are balanced by research showing that long-term health outcomes from consuming these oils are positive.
Cooking
In addition high-heat cooking methods - particularly deep frying - can lead to the formation of Advanced Glycation End Products (AGEs). AGEs form when fats or proteins react with sugars under high temperatures. They are naturally present in many cooked foods, but excessive intake of dietary AGEs has been linked to oxidative stress, inflammation, insulin resistance and an increased risk of cardiovascular disease in observational studies.
The concern with reheated seed oils in fast-food environments is twofold:
The accumulation of lipid oxidation products over time.
The production of additional AGEs due to repeated high-temperature exposure.
Note that AGEs are created on the surface of foods themselves, as part of the browning process of cooking - the maillard reaction - from frying, roasting, grilling etc. However, home cooking practices are unlikely to produce the same risks. Using oils with an appropriate smoke point, cooking at moderate temperatures, avoiding visible burning or charring and not reusing oil multiple times (a problem associated with fast foods or restaurants that reuse oils) can significantly reduce the formation of harmful byproducts.
Practical strategies to minimise exposure include:
Choose fresh, cold-pressed oils (olive oil) when possible for low-heat cooking.
Use high-smoke-point oils such as peanut, sunflower, or canola oil for frying if necessary.
Avoid smoking oils or visibly burnt foods.
Prioritise gentler cooking methods such as baking, steaming, poaching, or sautéing.
If you are particularly sensitive to oxidative stress (e.g., living with diabetes, cardiovascular disease or inflammatory conditions), discussing cooking strategies with your healthcare provider may be wise.
At the population level, it is clear that an ultra-processed, fried-food-heavy diet poses greater risk than moderate, thoughtful use of seed oils at home.
Next... Part 5: Seed Oils vs Saturated Fats: Clearing the Confusion
Final Thoughts
While seed oils can be a divisive issue online, we are relatively agnostic when it come to diet and eating patterns. If you enjoy cooking with olive oil, a dab of butter, avocado oil or (as a treat) duck fat, we do too. In the same regard, we are not concerned about a splash of canola in our stir fry and we try to avoid ultra-processed foods as part of our daily eating.
Changing health for the better is about progress, not perfection, and even small changes can make a meaningful difference over time. For most people, improving health is about finding motivation and prioritising self-care - with an ultimate goal of taking action. If you want to take effective and targeted steps that fit into your unique lifestyle and circumstances, The Whole Health Practice is here to help.
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Stay Healthy,
Alastair
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Related Studies
Uribarri J, Woodruff S, Goodman S, Cai W, Chen X, Pyzik R, Yong A, Striker GE, Vlassara H. Advanced glycation end products in foods and a practical guide to their reduction in the diet. J Am Diet Assoc. 2010 Jun;110(6):911-16.e12. doi: 10.1016/j.jada.2010.03.018. PMID: 20497781; PMCID: PMC3704564.
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