Olive Oil vs. Trans Fat: Two Fats, Two Completely Different Stories

Not All Fats Are Equal — Structure Determines Everything

For decades, 'fat' was a word that prompted caution in the grocery aisle. Yet nutritional science has long emphasised that not all fats behave the same way in the body. Olive oil and trans fat represent the sharpest possible contrast — two substances that share a category name while differing in almost every meaningful respect.

The properties of any fat are governed by the number of double bonds in its carbon chain and by the spatial arrangement of hydrogen atoms around those bonds. Unsaturated fatty acids carry at least one double bond, and depending on whether the hydrogen atoms on either side sit on the same face (cis configuration) or on opposite faces (trans configuration), the fat behaves very differently. Unsaturated fatty acids in natural plant-based oils are almost entirely cis-form. Trans fats, by contrast, arise when vegetable oils undergo industrial hydrogenation — a process that 'hardens' liquid oils into semi-solid fats — producing a configuration found only in trace quantities in nature.

This structural distinction has profound physical and chemical consequences. Trans fats remain close to solid at room temperature, much like saturated fats, which is why they were widely used in margarines, shortenings, and certain frying oils to deliver a crisp texture and an extended shelf life.

The Fatty Acid Profile of Extra Virgin Olive Oil

Extra virgin olive oil (EVOO) is dominated by oleic acid (C18:1), a cis-form monounsaturated fatty acid that accounts for 55–83% of its total fat content. The remainder consists chiefly of palmitic acid and linoleic acid. Trans fatty acid content is at or below detection limits: according to International Olive Council (IOC) standards, extra virgin grade oil must contain no more than 0.05% trans-oleic acid and no more than 0.05% combined trans-linoleic and trans-linolenic acids.

Several observational studies have reported that dietary patterns rich in monounsaturated fatty acids are associated with favourable cardiovascular markers. The PREDIMED study, published in the New England Journal of Medicine in 2013, reported that participants following a Mediterranean diet that included olive oil showed a tendency toward lower combined cardiovascular endpoints compared with the control group. It is important to note, however, that it is too early to attribute these associations to any single food; the results must be interpreted within the context of an overall dietary pattern.

EVOO also contains phenolic compounds such as oleocanthal and oleoaceein. Some studies have reported that these compounds may be associated with markers related to oxidative stress, though the research is ongoing. Polyphenol content varies considerably by cultivar, harvest timing, and processing method, so looking beyond the grade designation to available physicochemical analysis data is recommended.

Why Regulators Around the World Moved Against Trans Fats

In 2018, the World Health Organization launched the REPLACE initiative — a global plan to eliminate industrially produced trans fatty acids (iTFA) from the food supply. According to WHO data, industrial trans fat consumption is associated with an estimated 500,000 cardiovascular-related deaths per year worldwide.

In the United States, the FDA removed partially hydrogenated oils (PHOs) from its Generally Recognized as Safe (GRAS) list in 2018, effectively prohibiting their use in food. Denmark acted far earlier: in 2003, it became one of the first countries to cap trans fat content in foods at 2%, and studies published in the years that followed tracked subsequent changes in cardiovascular-related hospitalisation rates.

In many jurisdictions, nutrition labels are permitted to display '0 g' of trans fat when the amount falls below 0.5 g per serving, meaning trace quantities may still be present even when the label reads zero. Scanning the ingredient list for terms such as 'partially hydrogenated oil,' 'shortening,' or 'margarine' remains the most practical way to identify products that may contain industrial trans fats.

A Practical Guide to Choosing Fat at the Table

Three criteria are most commonly cited when assessing fat quality. The first is fatty acid composition: products with a higher proportion of monounsaturated and polyunsaturated fatty acids and minimal trans fatty acids are generally preferred in dietary guidance. The second is oxidative stability: because EVOO is high in oleic acid, it is considered relatively resistant to oxidation compared with oils higher in polyunsaturated fats. The third is degree of processing: extra virgin grade oil is obtained by physical cold pressing alone, without heat or chemical refining, which means minor bioactive components such as polyphenols are better preserved.

For everyday cooking, EVOO's smoke point of approximately 190–210°C makes it well suited to sautéing, stir-frying, finishing dishes, and salad dressings rather than sustained deep-frying at very high temperatures. Exposure to light, heat, and oxygen accelerates oxidation, so storing oil in a sealed container in a cool, dark place and using it reasonably quickly after opening is advisable.

Foods that commonly contain hidden industrial trans fats include margarines, commercially produced cookies and crackers, some microwave popcorn, instant noodle seasoning sachets, and non-dairy creamers. Developing the habit of reading ingredient lists is widely recommended as the most practical step toward reducing unintended trans fat consumption.

Nutritional science has long maintained that fat quality is not simply a question of eating less fat, but of choosing the right kind. The comparison between olive oil and trans fat stands as one of the clearest illustrations of how two substances with the same calorie density can carry entirely different implications — a difference that begins at the level of molecular geometry and extends all the way to the dinner table.