The basic fats of the matter

What are trans fats?

Trans fats, or trans fatty acids, form naturally in some meat and milk and artificially as a product of fats and oils altered by industrial processes. In the milk and meat of ruminant animals (cows and sheep) this occurs via bacterial activity in the stomach.

Artificially manufactured trans fats are created when vegetable oils are partially hydrogenated or "hardened" for use as spreads such as margarine, cooking fats for deep frying, and shortening for baking.

What's the problem?

There is compelling evidence that foods high in trans fatty acids increase low-density lipoprotein (LDL) or "bad" cholesterol levels and inflammation. This increases the risk of coronary heart disease, which can lead to a heart attack, and also increases the risk of stroke.

Unlike saturated fats, trans fatty acids also lower the levels of high-density lipoprotein (HDL), the "good" cholesterol. Gram for gram, trans fatty acids are two to five times more harmful to your heart than saturated fats.

How much trans fats are in our food?

New Zealanders obtain only 0.6 per cent of their daily kilojoules from trans fatty acids - below the World Health Organisation recommendation of 1 per cent. In most countries, trans fats come mainly from hydrogenated vegetable oils, but in some countries, like Denmark and New Zealand, we eat less processed trans fats and more dairy trans fats.

Which foods contain trans fats?

Trans fatty acids can be found in butter, margarine, table spreads, crackers, biscuits, snack foods, fried foods, baked goods, pastry, pies, cakes, and other processed foods made with partially hydrogenated vegetable oils.

The amount and kind of trans fats produced in milk and meat is determined by what the animal eats. New Zealand cows, which graze in rich pasture with clover produce more trans fats than those that are grain fed.

Food survey data shows that of the products with trans fat concentrations greater than 2g per 100g (the Danish limit), 60 per cent were products which contain ruminant fats.

Are trans fatty acids identified on food labels?

The Australia New Zealand Food Standards Code does not require manufacturers to list the trans fatty acid content of foods in the Nutrition Information Panel unless they make a nutrition claim about cholesterol, saturated, polyunsaturated, mono-unsaturated or trans fatty acids, or omega 3, omega 6 or omega 9 fatty acids.

Many edible oil spread manufacturers in New Zealand have chosen to voluntarily label their products.

Is the Government taking action to reduce trans fatty acids in food?

New Zealand has a non-regulatory approach to reducing the levels of trans fatty acids in the food supply. This contrasts with Canada, Europe and the United States, which have mandatory labelling for trans fatty acids in food and, in some cases, have placed limits on the permissions for trans fatty acids in processed foods.

* Adapted from Food Standards Australia New Zealand and New Zealand Food and Safety Authority information sheets; Review Report: Intakes of trans fatty acids in New Zealand and Australia (2009); Research papers published in the New Zealand Medical Journal.