Butter gets points for taste; margarine for being easy to spread. But the healthiest option is not strictly called butter or margarine - it's a 'spread'.
To improve the health of your heart, choose a spread with the lowest amount of saturated fat and trans fat per 100 grams. You will find this information in the 'per 100 grams' column of the nutrition information panel.
Butter contains about 50 per cent saturated fat, while margarine has a maximum of 20 per cent saturated fat. The fat content of "light" or fat-reduced spreads is lowered by replacing some fat with protein and water, meaning many are much lower than 20 per cent.
If you choose a full-fat spread (best for cooking), aim for less than 27 grams of saturated fat and one gram of trans fat per 100 grams. For fat-reduced spreads (best for bread and toast), aim for less than six grams of saturates and 0.2 grams of trans fat per 100 grams.
For a product to be called butter, it must be derived exclusively from milk and ingredients that are obtained from milk, including at least 80 per cent milk fat. It may also contain water, salt, lactic acid producing microorganisms and flavour-producing microorganisms.
When you see products in the supermarket that are packaged up like butter, or use words such as 'butter-flavoured' without specifically stating the product is butter, it's likely they have been altered in such a way that it no longer meets the content requirements above.
To call a spread margarine, the product must be a spreadable food made of edible oils and water, containing at least 80 grams of edible oils per 100 grams. It may also include water, edible proteins, salt, lactic acid-producing microorganisms, flavour-producing microorganisms and milk products.
Some margarines contain added plant sterols and stanols, a type of fat found in vegetable oil, nuts, legumes, grains, cereals, wood pulp and leaves, which are able to reduce cholesterol absorption from the small intestine into the bloodstream. If you have high blood cholesterol, you may want to use such a product, though you need to consume 20 to 25 grams per day for the maximum effect.
As soon as the fat content of margarine drops below 80 gram per 100 grams, it cannot technically be called "margarine". This is why the word "margarine" does not appear on labels for spreads that are fat-reduced. These are the healthiest options if you are trying to reduce your total fat and kilojoule intake.
If you are trying to lower your salt intake, check the sodium column on the nutrition information panel and aim for less than 400 milligrams per 100grams.
Cholesterol and saturated fat
Although the debate rages about the potency of specific fats in raising blood cholesterol, most Australians consume too much saturated fat from animal products. Saturated fat from foods and drinks gets manufactured in your body into low-density-lipoprotein (LDL) cholesterol, or commonly referred to as "bad" cholesterol, which then appears in your blood.
Excess LDL cholesterol that cannot be cleared by the liver ends up lining your artery walls. This makes your blood vessels hard and inflexible and they gradually become blocked. From there, it is just a matter of time before the blockage triggers a heart attack or stroke.
Saturated fat is a solid at room temperature and is the predominate fat found in the white fat in meat and dairy products, including milk, cheese, cream and butter.
Replacing butter for a spread that has a lower level of saturated fat is not the only change that can help lower your total saturated fat intake. For many Australians, the majority of their saturated fat comes from full-fat dairy, foods processed using palm oil or coconut oil, fried and fatty takeaway food, and packaged biscuits, cakes, pastries and dips.
The healthier fats are monounsaturated (avocados, almonds, cashews, peanuts, cooking oils made from sunflower, canola, soybean, olive, sesame and peanut) and polyunsaturated (omega-6 fats from sesame seed, margarine, linseed or flaxseed, sunflower and safflower oil, pine nuts and brazil nuts; omega-3 fats from walnuts, linseed and oily fish such as tuna, salmon, sardines and blue mackerel).
The one exception is trans fat. Technically it is an unsaturated fat. However, chemically it behaves exactly like saturated fat and increases LDL cholesterol. The problem is that trans fat also lowers HDL, the "good" cholesterol that carries circulating LDL back to the liver rather than it being deposited on artery walls.
In Australia, trans fat levels in spreads are among the lowest in the world. While most nutrition information panels indicate trans fat content of spreads, companies currently do not have to report it. When the nutrition information panel does not report trans fats, check the ingredients list for hydrogenated oil and partially hydrogenated vegetable oil, from which trans fats are derived.
No matter what the type of fat, they all have the same kilojoule value of 37kJ per gram. So, whether you opt for butter, margarine, a fat spread, nothing, or perhaps some avocado, hummus or tahini paste, keep an eye on the total saturated plus trans fat, and the kilojoules. And overall, try to choose foods that have a better fat quality.
* Clare Collins is a Professor in Nutrition and Dietetics at University of Newcastle