Avoiding trans fat

(1) Hydrogenated oil

Here, I refer to how to better reduce the intake of trans fat. As I mentioned in Trans fatty acid, trans fat exists in hydrogenated oils including margarine and shortening. Some of these processed oils do not contain trans fats. And such products would be claiming on the labels that "trans fat free" or "no hydrogenated oil" because nowadays people are increasingly well recognizing the adverse health effects of artificial trans fat. This leads us to speculate that fat products without such claims are highly likely to contain trans fats. As far as I have searched, trans fats account for around 10% in margarines and shortenings, though the percentage seems to vary depending on products or manufacturers. I strongly recommend you to evade these hydrogenated oils: not only refrain from buying a new product, but you should also scrap the products now in use.

Foods containing hydrogenated oils

Next, I mention processed foods containing margarine or shortening. You can learn whether margarine or shortening is in a product by reading the food label attached to the product. If the labeling is appropriate, ingredients are listed in descending order of weight, which you may also rely on to guess how much those fats are in it. You should be aware that margarine and shortening are often described as "processed oil" on food labels. The more margarine or shortening seems present in a food, the stronger you should reject it.

Hydrogenated oils are often used in porous foods including breads, cakes, donuts, cookies, and biscuits. Some of these foods, however, contain butter or palm oil instead of hydrogenated oil. You can tell whether the fat is hydrogenated or not by reading the food label. Note that evil manufacturers might disguise the labeling, taking advantage of the content's being difficult to identify: for example, stating butter despite using margarine with butter flavor. Therefore, you should be cautious in reading food labels to speculate the ingredients in foods. By the way, French breads usually do not contain fats, while other breads do, which is why it is harder than others. If you often have bread in your diet, take French bread.

(2) Foods that could contain hydrogenated oils

As of 2012 in Japan, there is no regulation in effect regarding trans fat, which I detail at Trans fat regulation. Two bodies, "Consumer Affairs Agency" and "Food Safety Commission", are dealing with this issue. Though, they are so reluctant to move forward to introduce trans fat regulation that they are not serving the public. Under such circumstances, consumers cannot help but guess the fat content of foods after gathering as much information as possible on their own. I observe below on some foods suspicious of having hydrogenated oil, which are also somewhat based on my speculation.

Vegetable oils

Some vegetable oils are lightly hydrogenated during refining process, which is not to harden vegetable oils. In the cases of soybean, rice bran, and other vegetables that are low in oils, oils are difficult to squeeze and so they are extracted by a chemical method - forcedly in a sense. However, this results in losing beneficial substances such as antioxidants in the vegetables. And there needs to prevent such vegetable oils from being oxidized, or rotting. To do this, alpha-linolenic acid and linoleic acid, which are easily oxidized, are hydrogenated to stand oxidization, followed by adding antioxidants to the oil. Meanwhile, oils extracted only by squeezing contain antioxidants innately existed in the vegetable, which enables the oil to endure for some time without hydrogenation or added antioxidants.

Under these circumstances, refined vegetable oils appear to contain about 1 to 2 percent as trans fat. You might be enough to take care of not taking in an excessive amount of refined oils, considering relatively small percentage of trans fat - some a tenth to a fifth of hydrogenated oil such as margarine and shortening. Nevertheless, if you have some worry, you may well choose vegetable oils that did not undergo a chemical process. Among them are sesame oil and extra virgin olive oil, which are available at supermarkets in Japan. If you cannot find favorite ones in the vicinity, on the Internet may serve your needs.

Snack foods

Snack foods such as potato chips and popcorn usually contain large amounts of fat. And that fat is said to be high in trans fat. But, the food labels fail to state that they contain margarine, shortening, or processed oil: instead, they oddly claim to have vegetable oil. If foods are fried with refined vegetable oils, trans fat should account for 1 to 2 percent. Not so might be because the frying oils are hydrogenated oil. I am not so confident in this point, though, you had better avoid snack foods.

To begin with, snack foods, as well as fast foods mentioned next, are called junk foods. A plenty of sugar and fat is often used in junk foods to make them tasty, with micronutrients - vitamins and minerals - kicked out. Junk foods are foods with extra processing that only to attract those people who simplistically choose not nutritious but delicious foods. These are far from being foods for civilized people. Junk foods deserve foods only when a person must eat something to evade starvation.

Fast foods

Fast food restaurants serves hamburgers, French fries, fried chickens, pizzas, donuts, and so on, which contain a lot of fat. And in many cases, the fat is said to be shortening. I point out that a majority of fast food restaurant is offering take-out services. This could explain why they use hydrogenated oil: to keep the foods' taste and volume (and the customers) even a while after cooking. Some shops claim to have started replacing the conventional hydrogenated oil with ones that have less trans fat. In any case, you need not drop in at fast food restaurants to undermine your health if you have other choices.

Eating out foods

If you frequently eat out (go to restaurants or order lunch boxes), you need take care of fries and tempuras. When you are confident that the fried foods you eat contain little hydrogenated oil, for example, by asking the cook, there is little problem as for trans fat. But in many cases, it would be difficult to know that. So, you should choose menus that include less fries when eating out. If you have no choice but to eat a serving with fries, then you may take measures to leave the coatings of fries.


Mayonnaise is made around 70% out of oil. You might think that mayonnaise possibly contains some hydrogenated oil, as it is viscous. However, such a worry would be unnecessary: mayonnaise consists of vegetable oil, vinegar, and eggs as emulsion, which bring its viscousness. Then, even if the vegetable oil in a mayonnaise has been lightly hydrogenated, trans fat in the mayonnaise is expected to be merely around 1%. You do not need to completely reject mayonnaise unless you eat it too much.


Butter contains no artificial trans fat, as it derives from milk. Nevertheless, I dare mention this food. I am not saying you should avoid naturally occurring trans fat in the ruminant: you need not avoid it in dairy products because it is different from artificial trans fat despite the same name "trans fat". I mean that you must take a genuine butter.

In the time of fierce economic competition and lax penalties on illegalities, the situation seen now in Japan, businesses are more prone to do whatever they can to make profit. To apply this to margarine manufacturers or butter companies, what can happen? They might fabricate margarine-bled butter or butter-flavored margarine, using margarine that is cheaper than butter, and sell them as butter. As a result, consumers run the risk of buying and eating, without notice, "a fake butter" with artificial trans fat instead of a genuine butter. This is not a imaginary story: in fact, I recently found at a supermarket a product that claims to be the mixture of butter and margarine.

Fatty Acids and Health

What is a fatty acid?
Trans fatty acid
Trans fat regulation
Avoiding trans fat
Taking omega-3 fatty acid


Trans fat (Health Canada)
Information on trans fatty acid (Consumer Affairs Agency)
Information on trans fatty acid (Ministry of Agriculture, Forestry and Fisheries)

© 2007 Takashi Shimazaki
Updated: April 14, 2013