BBC Radio 4 this morning had a brief item about margarine. The item focused on the fact that margarine manufacturers can trumpet the presence of ‘heart-healthy’ omega-3 fats on the label. Professor Jack Winkler, Professor of Nutrition Policy at London Metropolitan University made the claim that such labelling is misleading. It seems that margarine manufacturers are putting ‘cheap’ plant-based omega-3 fats (I assume alpha linolenic acid) and kinda passing them off as fish oils. Professor Winkler appeared to claim that fish-derived omega-3 fats have proven cardiovascular benefits that do not extend to plant-derived omega-3. What he wants is for food manufacturers to be able to make claims about the omega-3 content of their products, but only if they contain actual marine omega-3. Seems fine to me.

But why stop there? Why not look and see what evidence there is for the other nutritional attributes of this ‘food’?

The major constituents of margarine are ‘vegetable’ oils, obtained from foods such as sunflower seeds, rapeseed or soya beans. These oils are usually extracted using the application of pressure and heat, and maybe the use of solvents too. This processing can damage the fats and impart some unhealthy properties on them. The oil obtained by this process is then treated with sodium hydroxide to ‘neutralise’ certain fats in the oil that are unstable and may cause spoilage. After this, the oil is then bleached, filtered and steam-treated to produce what is essentially a colourless, flavourless liquid.

To convert this into margarine, this oil is subjected to chemical processes such as interesterifcation or hydrogenation. Interestification involves the use of high temperature and pressure, along with enzymes or acids, to ‘harden’ the oil. In hydrogenation, hydrogen is bubbled through the oil at high temperature. The ‘partially-hydrogenated’ fats so produced can be tainted with trans fats that are strongly linked with heart disease. As a result, manufacturers now use interesterification as their preferred processing method. However, question marks remain regarding the health effects of these fats [1] – a situation that is essentially the same as the one when partially hydrogenated fats were introduced into the food supply and lauded as a healthy step forward.

After this, hydrogenation or interesterification, the solidified fat is generally blended with other fats, which can be of vegetable or animal origin. And then the product needs to be both coloured and flavoured. Then, what are known as ‘emulsifying agents’ are added to prevent the product from separating out. And finally, the end result is extruded into a plastic tub.

While margarine is passed off as something generally healthy, it is (in my view) a highly-processed, chemicalised food that does not really deserve the title of ‘food’ at all. It was originally sold to us on the basis that it is low in heart-stopping’ saturated fat, and therefore a healthy alternative to butter. However, hard as one looks, there is really no good evidence that saturated fat causes heart disease.

Oh, and then we have margarine’s cholesterol-reducing properties. Except that taking dietary steps to reduce cholesterol does not appear to have broad benefits for health.

And even if cholesterol-lowering did have apparently miraculous health benefits, does that mean that something that reduced cholesterol must be healthy. If a known poison was found to reduce cholesterol, would that somehow make it ‘healthy’? What is critically important is not the impact of a food (or anything else) on cholesterol levels, but it’s impact on health.

So, what does the science show in this regard?

One study in the scientific literature which examined the association between butter and margarine consumption and risk of heart disease in men [2]. This study found that butter consumption was not associated with heart disease risk. In other words, those men eating more butter were not at increased risk of suffering from heart disease. On the other hand, margarine consumption was associated with an increased risk of heart disease: in the long term, for each teaspoon of margarine consumed each day, risk of heart disease was found to be raised by 10 per cent.

In another study [3], this one in women, long-term margarine consumption was associated with a 67 per cent increased risk of heart disease. These studies are old, but I’m not able to find any newer ones. Some say these studies reflect what we know about trans fats, but now we have interesterified fats, there’s no cause for concern. However, as I pointed out above, the health effects of these fats are essentially unknown. In my opinion, we really are not in a position to declare these fats as healthy. They may not even be safe.

It appears as though there is no good evidence that margarine is healthier than butter. In fact, the evidence suggests butter is the preferred choice (it also tastes better, of course). The marketing of margarine to the masses seems distinctly unscientific and misleading to me, whatever the source of omega-3 fats it may contain.

References:

1. Karupaiah T, et al. Effects of stereospecific positioning of fatty acids in triacylglycerol structures in native and randomized fats: a review of their nutritional implications. Nutrition & Metabolism 2007;4:16

2. Gillman MW, et al. Margarine intake and subsequent coronary heart disease in men. Epidemiology. 1997;8(2):144-149

3. Willett WC, et al. Intake of trans fatty acids and risk of coronary heart disease among women. Lancet. 1993;341(8845):581-5