Updated 11 March 2013

Butter vs. margarine: the latest

The unearthing of previously hidden clinical trial data has renewed the focus on the butter vs. margarine debate.

For decades the cornerstone of dietary advice to patients with raised blood fat levels has been to encourage these potential heart disease sufferers to reduce how much saturated fat they eat and to increase their unsaturated fat intakes. At the beginning of February, this approach was turned upside-down by the retrieval of so-called "lost research results" showing that contrary to our belief that unsaturated fats are beneficial, these fats may have the potential to increase the risk of death from heart attacks and cardiovascular disease (BMJ, 2013A).

The status quo

Currently most heart diets are high in poly- and monounsaturated fatty acids derived from plant oils (maize, sunflower, safflower, canola and soybean oils) and soft or tub margarine made from these oils. Such heart-healthy diets also contain less saturated fatty acids (i.e. cream, butter, eggs, fatty meat, hard margarine, and processed foods like cakes, pies, pastries and confectionary containing saturated fats).

Now researchers such as Prof Philip Calder, Professor of Nutritional Immunology, Human Development and Health Academic Unit, Faculty of Medicine, at the University of Southampton in the UK, state that the nutritional advice propagated by such authoritative bodies as the American Heart Association for the use of persons with heart disease, may be doing more harm than good (Calder, 2013). A conundrum of epic proportions!

Hidden clinical trial data

Most scientists and individuals doing research in the fields of pharmacy, medicine, nutrients and other healthcare-related subjects, have probably long suspected or been aware of the fact that a great many research results are not published. This is what has become know as "hidden clinical trial data". According to the British Medical Journal (BMJ), which is a highly respected scientific and medical journal, "it is well documented that researchers and companies often withhold clinical trial results from doctors and patients. Half of all trials are never published". (BMJ, 2013B).

The BMJ is now calling for researchers to make this "hidden clinical trial data" available by publishing it so that we, the public, can make up our own minds about the efficacy of medical treatments, as well as dietary recommendations. In 2012, the BMJ published a special edition devoted to "hidden clinical trial data" (BMJ, 2013B).

In response to this action taken by the BMJ, a group of Australian researchers did an in-depth analysis of the effects of omega-6 linoleic acid (the most common polyunsaturated fatty acid [PUFA] in Western diets) based on previously "missing" data from the Sydney Diet Heart Study which had been conducted from 1966 to 1973, which ultimately indicated that increasing our polyunsaturated fatty acid intake and thereby our intake of linoleic acid, may not be the answer to heart disease prevention after all (BMJ, 2013A).
The Sydney Diet Heart Study
This study involved 458 men aged 30-59 years who had recently suffered a coronary event, such as a heart attack or an episode or angina. The subjects were randomly divided into two groups: the study group were instructed to reduce their intake of saturated fats to less than 10% of their energy intake and to increase their intake of linoleic acid (provided by safflower oil and margarine made from this oil) to 15% of their energy intake. Safflower oil is a particularly concentrated form of omega-6 linoleic acid, but does not provide any omega-3 PUFAs (these omega fatty acids are know to be in short supply in modern western diets and may contribute to the degenerative diseases modern mankind suffers from).

The control group were not given any dietary advice. Both groups participating in the Sydney Diet Heart Study were regularly assessed and had to complete food diaries for more than 3 years (BMJ, 2013A).

Disturbingly, the results showed that high intakes of omega-6 linoleic acid led to an increased risk of death from all causes, as well as from cardiovascular disease, in the study group.

Understandably these "new" results which have been revealed by making previously "hidden clinical trial data" available, are regarded as vital in our understanding of which fats interact with our bodies to cause diseases.

Prof Philip Calder, says that this re-analysis of old data, “provides important information about the impact of high intakes of omega-6 PUFAs, in particular linoleic acid, on cardiovascular mortality at a time when there is considerable debate on this question.” The debate Prof Calder is referring to, is the recent American Heart Association recommendation that Americans should not only maintain, but increase their intakes of omega-6 PUFAs, which in the light of these “new-old” findings may not have the desired beneficial effect (Calder, 2013).

Another blow to PUFA spreads

An article also based on this previously missing, but now newly revealed data on "Heart attack risk in 'healthy spreads'", featured in February 2013 on the Express website in the UK, reports that vegetable fats have been found "to trigger inflammation, which plays a major role in chronic illnesses from heart disease and cancer to arthritis and Alzheimer’s". The inflammation trigger is caused by the conversion of linoleic acid to arachidonic acid in the human body (Express, 2013).

What do we do now?

In the light of these new revelations that are emerging thanks to the publication of "missing data", our concept of what to advise people with raised blood fat levels, potential heart disease victims and patients with cardiovascular disease, has effectively been upended.  

The field of heart disease prevention via diet is not the only area that will be shaken by such tremors as more and more "hidden data" will be made available and many a trusted medication will also be shot down in flames.
I believe that the first Food-Based Dietary Guideline that encourages us to "Eat a Variety of Foods" is probably the best solution while we wait for nutrition researchers to sort out the conundrum regarding our use of dietary fats to change the outcome of heart disease. Thus we can probably eat some butter and some soft margarine and some plant oils, but in small quantities. Try measuring out how much of these fats and oils you use for a few days to see for yourself if you are eating an excess of any type of fat. And if possible, have a serving or two of fatty fish or take salmon oil capsules to boost your omega-3 intake.

(References: BMJ (2013A). Study raises questions about dietary fats and heart disease guidance. ;BMJ (0213B). Open data. ;Calder PC (2013). Old study sheds new light on the fatty acids and cardiovascular health debate. British Medical Journal, 2013;346:1492; Express (2013). Heart attack risk in ‘healthy spreads’. Published online on 7 February 2013.

(Photo of woman eating buttered bread from Shutterstock)


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