Trans-fatty acids have been hypothesised to be carcinogenic, although there is limited data in humans testing this hypothesis. A diet laden with margarine could increase cancer risk and is also associated with heart disease.
Both glycidol and 3-MCPD are harmful by-products of heating vegetable oil to higher than 200 degrees Celsius, occurring most when the oil is refined to remove volatile or bad-smelling materials.
When that refined oil is used in margarine, the two compounds often go in with it.
The International Agency for Research on Cancer, under the World Health Organisation, classes glycidol and 3-MCPD as class-2 carcinogens – both “possibly carcinogenic”, based on animal tests.
The European Food Safety Authority (EFSA) classifies glycidol as “genotoxic and carcinogenic”, meaning it may damage DNA and cause tumours.
In a study published in the National Library of Medicine, the intake of trans fatty acids from partially hydrogenated vegetable oil in relation to cancer risk was further investigated.
A total of 77,568 men and women were followed up through 2007, during which time 12,004 cancer cases occurred.
“Intake of trans fatty acids (TFA) may influence systemic inflammation, insulin resistance and adiposity, but whether TFA intake influences cancer risk is insufficiently studied,” began the study.
The research found that trans-fat in margarine is associated with an increased risk of lung, colon, rectum, breast, endometrium and prostate cancers.
It’s important to note that not all kinds of margarine are the same recipe, and therefore they can have different health impacts.
A study published in Harvard Health Publishing said: “Today the butter-versus-margarine issue is really a false one.
“From the standpoint of heart disease, butter remains on the list of foods to use sparingly mostly because it is high in saturated fat.
“Margarines, though, aren’t so easy to classify.
“The older stick margarines turned out to be clearly worse for you than butter.
“Some of the newer margarines that are low in saturated fat, high in unsaturated fat, and free of trans fats are fine as long as you don’t use too much (they are still rich in calories).”
“Not all margarines are created equal, and some margarines contain trans-fat,” added Dr Katherine Zeratsky.
“In general, the more solid the margarine, the more trans-fat it contains.
“So, stick margarines usually have more trans-fat than tub margarines do.
“Trans-fat, like saturated fat, increases blood cholesterol levels and the risk of heart disease.
“In addition, trans fat lowers high-density lipoprotein (HDL), or ‘good,’ cholesterol levels.”
She concluded: “Skip the stick and opt for soft or liquid margarine instead.”
Saturated fats are found in animal sources of food such as meat, poultry, butter and cheese.
They’re also found in tropical oils like coconut, palm and palm kernel oils.
Trans fats are found in foods that are made with or cooked in partially hydrogenated fat.
Some crackers, potato chips, baked goods, deep-fried fast foods and margarines contain trans fats.
It’s best to avoid these types of fats – or make them a once-in-a-while part of your diet.