Butter vs margarine – the debate spreads
Published: 17 May 2016
Nutrition is like fashion – trends fade into the background, only to regain popularity a few years down the track. Right now, the hot topic is whether we should be using butter or margarine. It’s an old debate that’s once again ‘rearing its head’.
Sparking this fresh debate was an article published in the British Medical Journal (April 2016) about newly discovered data from the Minnesota Heart Study, a 50-year experiment on how fats affect our health (1). The article reports that swapping saturated fat for vegetable oil may not in fact be better for our hearts. More alarming still, it states that too much vegetable oil could actually increase our risk of heart disease, rather than reduce it. The resulting sensational media headlines have cast doubt into the minds of even the most loyal margarine users.
But what did the research really say? Should we go back to spreading lashings of butter on our bread (whole grain, of course)?
By taking a closer look at the Minnesota Heart Study, it’s clear the results are not all they seem to be. Here are some reasons why:
- The study involved older adults who had been admitted into care because they were ill. That means the results cannot be generalised to a healthy younger population living outside of institutionalised care.
- The vegetable oil used in this study was predominately linoleic acid (an omega-6 fatty acid) in the form of corn oil and corn oil polyunsaturated margarine. The amount of linoleic acid given to research subjects was about double the amount eaten by most Americans. So, it’s possible those people involved in the study were having too much of a good thing; the amount they ate was undoing any potential benefits.
- Unfortunately the trial did not include the addition of any omega-3 fats to the diet, only omega-6. Since the completion of the trial some 50 years ago, we have learnt more about the importance of including both omega 3 fatty acids and omega 6 fatty acids in the diet to reduce the risk of heart disease. As with most things, balance reigns supreme.
- Only one quarter of participants followed the diet for more than a year. Altering a person’s diet for a short period of time, especially among unwell older adults, does not necessarily affect long-term health outcomes, such as heart disease.
- As the corn oil was used in place of the usual cooking fats, it’s possible that heating the corn oil during cooking was responsible for some of the trial’s negative effects. Since the original trial was completed, we’ve learned more about the instability of polyunsaturated oils. Here’s a blog about the effects of heating of oils.
What’s the verdict: butter or margarine?
The results of this study don’t provide strong enough evidence that we should be switching from vegetable oils or margarine back to butter. The bulk of evidence still tells us that replacing saturated fats with unsaturated fats, particularly polyunsaturated fats (including both omega 3 and omega 6), helps reduce our risk of heart disease (2).
Butter is the biggest source of saturated fat in the Kiwi diet. While using small amounts of butter every now and then shouldn’t be a problem for most people, the clear, unequivocal evidence remains that it is better for our hearts to replace saturated fats (such as butter, coconut oil and fatty meat) with unsaturated fats. Making the simple swap from butter to margarine spreads is one way to do this.
Other sources of healthy unsaturated fats include: nuts, seeds, oily fish, avocado and plant oils, such as cold-pressed olive, avocado or canola oil. For those who choose not to use margarine spreads, consider avocado, hummus and nut or seed butters as good options for a less-processed, more whole food approach, or use no spread at all.
See the bigger picture
Putting aside the butter versus margarine debate, we need to remember that it’s our whole dietary pattern that counts. Despite what some one-off studies may report, the total available evidence tells us that a heart-healthy dietary pattern is based largely on minimally-processed foods and includes plenty of vegetables and fruit; some whole grains in place of refined grains; legumes; nuts; seeds; and other sources of healthy fats such as oily fish; and may contain non-processed lean meats or poultry and/or dairy.
By following this pattern, the fats in our diet will take care of themselves.
(1) Ramsden CE, Zamaora D, Majchrzak-Hong S, et al. Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73). BMJ, 2016;352:i1246.
(2) Mozaffarian D, Micha R, Wallace S (2010) Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. PLoS Med 7(3): e1000252.
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