Partially Hydrogenated Vegetable Oil

What is partially hydrogenated oil?

Hydrogenation is the process of solidifying liquid vegetable oils by adding hydrogen to them with the help of a catalyst. When the process is stopped before completion, in other words when the oil is partially hydrogenated, some of the fatty acids are converted into the “trans” structure, which is rare in nature.

For many years these oils were widely used in margarine, frying oils and pastries, because they were cheap, extended shelf life and gave products the desired crisp or creamy texture. Fully hydrogenated oils, on the other hand, contain no trans fat; they are converted into saturated fat and are assessed differently.

Which products may contain it?

• Old-style margarine and solid vegetable fats (“vegetable margarine”)
• Ready-made cakes, cookies, biscuits and puff pastry
• Fried fast food and frying oils that are reused again and again
• Coffee creamer, ready-made whipped topping and some frozen pastries
• Microwave popcorn and some confectionery

On the label it appears as “partially hydrogenated vegetable oil”, “partially hydrogenated oil” or “vegetable oil (partially hydrogenated)”. Because of regulatory changes, this term is now seen far less often on packaged products than in the past.

Is it harmful? The scientific assessment

The health effect of trans fats is one of the clearest findings in nutrition science. Industrial trans fats raise LDL cholesterol, lower HDL cholesterol and increase inflammatory processes. The World Health Organization states that trans fat intake contributes to a large number of deaths from heart disease worldwide every year.

For this reason, in 2018 the WHO launched an action plan to eliminate industrial trans fats from the global food supply entirely and called on countries to introduce legal limits. In the United States, the FDA revoked the “generally recognised as safe” (GRAS) status of partially hydrogenated oils; the EU has also set a legal limit on the amount of industrial trans fat in foods.

In Türkiye, too, a 2020 regulation under the Turkish Food Codex limited industrial trans fat in foods supplied to the final consumer to 2 grams per 100 grams of total fat. However, natural trans fats (found in small amounts in dairy and meat products) are outside this limit and are assessed differently.

Who should be careful?

• Everyone: No safe lower limit has been defined for industrial trans fat; it is recommended to eat as little as possible.
• People at risk of cardiovascular disease: Avoiding it is even more important for people with high cholesterol, diabetes or a family history of heart disease.
• People who often eat out: With unpackaged products and fried restaurant food, it is impossible to tell from a label which fat has been used.

What to do when you see it on a label

If you see the words “partially hydrogenated” in the ingredient list, looking for an alternative to that product is in line with the recommendations of health organisations. Because trans fat may not be listed separately in the nutrition table, reading the ingredient list is a more reliable approach. As alternatives, you can choose liquid oils such as olive, sunflower or hazelnut oil and products stated to contain no trans fat. Palm oil contains no trans fat, but is high in saturated fat.