An Australian Institute of Health and Welfare report in 1994 quoted industry sources that put 1992 market shares of butter and margarine at 26.1 per cent and 73.9 per cent respectively. In the late ’90s, margarine sales began to decline. In 2015  Roy Morgan research showed that butter was making a comeback, with more people buying butter than margarine.

Margarine enjoyed at least two decades of popularity as a healthier alternative to butter. Until the mid-1970s the industry had been subject to government quotas designed to protect dairy farmers. It was deregulated in 1975 and 1976 by the Federal, New South Wales and South Australian governments. At the same time, there was increasing publicity about cholesterol and its supposed role in heart disease.  The increased availability of the product and its reputation as a healthier choice (backed by significant advertising campaigns) saw margarine sales rise.

However, 1993 was a turning point. In the United States, Professor Walter Willett published data from a long-term study showing that the trans fats produced when vegetable oils were hardened by hydrogenation were potentially even worse than cholesterol.  Women in the study who consumed a lot of trans fats were twice as likely to have a heart attack as those who consumed fewer. The professor even called hydrogenation “the biggest food-processing disaster in US history”. The results of the study had press coverage in Australia.

As this information became known, margarine sales suffered. While most manufacturers scrambled to change their processes to remove trans fats, consumer confidence in the health benefits of margarine was dented. In 1998, AC Nielsen pegged margarine as the third-fastest declining category in supermarket sales, down 4 per cent for the year.

The balance between butter and margarine sales has continued to shift in favour of butter. The Roy Morgan research found that butter buyers were more likely than margarine buyers to enjoy cooking, entertaining spontaneously and trying new and exotic foods. They were also more likely to be looking for unprocessed, additive-free foods. Margarine buyers were more likely to buy house brands, treat cooking as a chore and put convenience ahead of taste.

In 2018, butter was still well ahead of margarine. Forty-two per cent of Australians bought butter in the average month and 13% bought a butter blend or dairy spread, compared to the 25% who bought margarine.

The change in market behaviour has led Unilever to ditch some of its most popular margarine brands. However, the Heart Foundation continues to recommend margarine in preference to butter.