Quick answer: Partially hydrogenated oils can produce industrially manufactured trans fats, which are associated with an increased risk of coronary heart disease. However, partially hydrogenated and fully hydrogenated oils are not the same, and the word “hydrogenated” alone does not tell the complete nutritional story.
The most useful step for shoppers is to read the full ingredient list, understand the type of fat being used and avoid assuming that every vegetable oil, shortening, margarine or butter product has the same composition.
What Are Hydrogenated Oils?
Hydrogenation is a process that changes the structure of an oil by adding hydrogen. Food manufacturers have used this process to make liquid oils firmer, improve stability and create particular textures in products such as spreads, pastries, biscuits and commercial baked goods.
Hydrogenation can also help a fat remain stable for longer or perform differently during manufacturing. However, there is an important distinction between partial hydrogenation and full hydrogenation.
These terms should not be treated as interchangeable. Most health concerns about industrial trans fats relate specifically to partially hydrogenated oils.
Partially Hydrogenated vs Fully Hydrogenated Oils
| Feature | Partially Hydrogenated Oil | Fully Hydrogenated Oil |
|---|---|---|
| How extensively it is hydrogenated | Only some unsaturated bonds are hydrogenated | Hydrogenation is carried much further |
| Industrial trans fat | Can contain significant industrially produced trans fat | Generally contains little or no trans fat created by the process |
| Typical texture | Semi-solid and suitable for some shortenings or spreads | Harder and more highly saturated |
| Main nutritional concern | Industrial trans-fat content | Overall saturated-fat content and total dietary context |
Partial hydrogenation can change some of the unsaturated fatty acids into trans-fatty acids. This is why partially hydrogenated oils became a major source of industrial trans fat in processed foods.
Full hydrogenation changes more of the oil’s unsaturated bonds. It generally does not create the same trans-fat profile as partial hydrogenation, although the resulting fat may be more highly saturated.
This does not mean that a fully hydrogenated fat is automatically nutritious or suitable for every diet. It simply means that the two processes should not be described as though they create exactly the same type of fat.
What Are Trans Fats?
Trans fats, also called trans-fatty acids, are a type of unsaturated fatty acid. They can come from two broad sources:
- Industrially produced trans fats, commonly associated with the partial hydrogenation of oils
- Naturally occurring ruminant trans fats, found in small amounts in meat and dairy products from animals such as cows and sheep
The existence of natural trans fat in dairy products is an important detail. It means that statements such as “butter contains no trans fat” are not technically accurate.
Butter does not contain industrial trans fat created by partially hydrogenating vegetable oil. However, because butter is a dairy product, it may naturally contain small amounts of ruminant trans-fatty acids.
Why Are Industrial Trans Fats a Concern?
Industrial trans fats are a concern because they can adversely affect blood cholesterol. They can raise low-density lipoprotein cholesterol, commonly called LDL cholesterol, and may lower high-density lipoprotein cholesterol, commonly called HDL cholesterol.
Higher consumption of industrial trans fats is associated with an increased risk of coronary heart disease. For this reason, health authorities including the World Health Organization have recommended eliminating industrially produced trans fats from the global food supply.
This does not mean that eating one biscuit containing a particular fat will directly cause disease. Nutrition risk depends on the amount consumed, how frequently it is consumed and the overall dietary pattern.
Accurate food information should explain risk without turning every ingredient list into a medical emergency.
Are Trans Fats the Same as Saturated Fats?
No. Trans fats and saturated fats are different types of fatty acids.
Butter, coconut oil, palm oil, shortening and margarine can have very different proportions of saturated, unsaturated and trans fats. The exact profile depends on the ingredient, its source and how it has been processed.
A food can be free from partially hydrogenated oil while still containing saturated fat. Similarly, a product made with vegetable oil is not automatically free from industrial trans fat unless the type of oil and processing method are known.
For this reason, labels should be read as a whole rather than reducing every product to a single marketing phrase such as “made with vegetable oil”, “made with butter” or “trans-fat free”.
Why Were Partially Hydrogenated Oils Used in Food?
Partially hydrogenated oils were used because they offered several practical manufacturing properties. Depending on the formulation, they could:
- Create a firm or semi-solid texture
- Help pastries and biscuits develop a short or flaky structure
- Improve stability during storage
- Withstand certain commercial production conditions
- Provide consistent results across large production runs
These functions help explain why partially hydrogenated oils were once common in shortenings, margarines, commercial baked goods and fried foods.
Many countries have since introduced restrictions, limits or other measures intended to reduce industrial trans fats in the food supply. Regulations and labelling requirements are not identical in every country, so shoppers should not assume that a rule from one market applies everywhere.
How to Read a Food Label
When checking a packaged food, start with the ingredient list. Look for clear and specific descriptions of the fat source.
Words That Deserve Closer Attention
- Partially hydrogenated vegetable oil
- Partially hydrogenated soybean, canola, cottonseed or palm oil
- Hydrogenated vegetable fat
- Vegetable shortening
- Margarine
- Vegetable fat or vegetable oil without further detail
The presence of “partially hydrogenated” is the clearest sign that the ingredient may be a source of industrial trans fat.
Terms such as shortening or margarine do not automatically prove that a product contains partially hydrogenated oil. Modern shortenings and margarines can be made using different processes and fat blends. The full ingredient declaration is more useful than the product category alone.
Check Both the Ingredient List and Nutrition Panel
Nutrition-labelling rules differ between countries. In New Zealand and Australia, trans-fatty acids generally do not have to be listed in the nutrition information panel unless the manufacturer makes certain nutrition claims relating to fats or cholesterol.
This means the absence of a separate “trans fat” line does not necessarily confirm that a product contains none. Reading the ingredient list can provide additional context.
In other markets, including the United States, trans fat may be shown differently on the nutrition panel. Serving-size rules and rounding requirements may also vary. A label should therefore be interpreted according to the rules of the country in which the product is sold.
Does “Zero Trans Fat” Tell the Whole Story?
Not always.
A “zero trans fat” or similar claim must be understood within the local labelling rules. Some countries allow nutrient values to be rounded when the amount per serving falls below a specified threshold.
Serving size also matters. A very small declared serving can make the amount shown on a nutrition panel appear lower, even when a person usually eats several servings at once.
However, this does not mean every zero-trans-fat claim is misleading. It simply means shoppers should check:
- The declared serving size
- The number of servings normally eaten
- The complete ingredient list
- Whether partially hydrogenated oil is present
- The country whose labelling rules apply
Are All Vegetable Oils Unhealthy?
No. “Vegetable oil” describes a broad group of oils, not one single nutritional category.
Olive oil, canola oil, sunflower oil, soybean oil, coconut oil and palm oil have different fatty-acid profiles and different uses. They may also be refined, blended, interesterified, partially hydrogenated or used without hydrogenation.
It is therefore inaccurate to describe all vegetable oils as dangerous simply because partially hydrogenated vegetable oil can contain industrial trans fat.
The more useful question is not simply, “Is this a vegetable oil?” It is:
- Which oil or fat is being used?
- Has it been partially hydrogenated?
- What role does it play in the food?
- How much of the food is normally consumed?
- How does it fit into the overall diet?
Is Butter Automatically a Healthier Alternative?
Butter and partially hydrogenated vegetable oil are different ingredients, but that does not make butter an unrestricted health food.
Butter contains saturated fat and naturally occurring ruminant trans fats. It should not be promoted as heart healthy, anti-inflammatory or automatically healthier than every vegetable oil.
In baking, butter is often selected for its flavour, aroma, melting behaviour and effect on texture. These are culinary characteristics, not proof of a health benefit.
Cultured butter has a deeper and more developed dairy flavour than many regular sweet-cream butters. To understand that flavour distinction, read our guide to cultured butter versus regular butter.
How This Relates to Butter Cookies
Different butter cookies use different fat systems. A recipe may use:
- Butter
- Vegetable oil
- Shortening
- Margarine
- A combination of dairy and vegetable fats
These choices affect flavour, aroma, cost, texture, melting behaviour and storage stability. They do not all produce the same type of cookie.
If you specifically want a butter-focused cookie, check whether butter is clearly named in the ingredient list and whether the butter percentage is disclosed. Our guide to identifying quality butter cookies explains the other information worth checking, including texture, net weight, flavour ingredients, origin and allergens.
Lowrey Original Butter Cookies use four main ingredients:
- New Zealand cultured butter
- Wheat flour
- Corn starch
- Icing sugar
The Original recipe contains approximately 42% New Zealand cultured butter. It is egg-free and has no added salt.
This information explains the product’s ingredients and intended buttery flavour. It should not be interpreted as a claim that butter cookies are a health food or that they can be eaten without considering portion size.
Lowrey also makes Coffee, Chocolate, Matcha, Raspberry and Black Sesame Butter Cookies. These flavours include additional ingredients specific to each flavour, and every tin contains one flavour rather than mixed flavours.
You can view the six single-flavour options in the Lowrey Butter Cookies collection or read what Lowrey Butter Cookies are.
Frequently Asked Questions
Does Every Hydrogenated Oil Contain Industrial Trans Fat?
No. Partially hydrogenated oils are the main concern because partial hydrogenation can produce industrial trans fats. Fully hydrogenated oils generally contain little or no trans fat created by the process, although they may contain more saturated fat.
Does Butter Contain Trans Fat?
Butter may naturally contain small amounts of ruminant trans fat because it is made from cow’s milk. This is different from industrial trans fat produced through partial hydrogenation.
Is Vegetable Shortening Always Partially Hydrogenated?
No. Shortening describes the function and physical form of a fat, not one fixed manufacturing process. Some modern shortenings are made without partially hydrogenated oils. Check the complete ingredient list.
Can I Identify Trans Fat from the Nutrition Panel Alone?
Not in every country. In New Zealand and Australia, trans fat is not always required as a separate line in the nutrition information panel. The ingredient list can therefore provide important additional information.
Does “Made with Butter” Mean a Cookie Contains Only Butter as Its Fat?
Not necessarily. Some products combine butter with vegetable oil, margarine or shortening. Check the complete ingredient list and any disclosed butter percentage.
Are Foods Without Partially Hydrogenated Oil Automatically Healthy?
No. Removing one ingredient does not determine the nutritional quality of the whole food. Total fat, saturated fat, sugar, serving size, frequency of consumption and the overall diet still matter.
The Bottom Line
Partially hydrogenated oils can be a source of industrial trans fats, but not every hydrogenated oil is identical. Partial and full hydrogenation produce different fat profiles, and natural trans fats can also occur in small amounts in dairy and meat.
When comparing packaged foods, read the full ingredient list, check the serving size and interpret nutrition claims according to the rules of the country where the product is sold.
For butter cookies, the ingredient list can also tell you whether the product is built around butter, vegetable fat or a combination of fats. That information is more useful than dramatic claims about “good” and “bad” ingredients.
