The famous “You oughta be congratulated” advertising jingle and television campaign was designed to assure mums that Meadow Lea Margarine would not only help their families to avoid the evils of butter but actually tasted good. Created by Alan Morris and Alan Johnson – the “Mo” and “Jo” of Mojo Advertising – it became one of the most famous ad campaigns of its time.

In the 1970s, we started to give up butter. This was based on pronouncements from health authorities that saturated fats in dairy products,  meat and even eggs would raise your cholesterol levels and expose you to an increased risk of heart disease. Cholesterol became the new dietary devil, based on studies that began in the 1950s suggesting that it played a role in causing atherosclerosis, or hardening of the arteries.

Switching to margarine from butter was seen to be a way to cut down on saturated fat. The problem was that the early margarines were produced by subjecting vegetable oils to chemical processes that produced something even worse: trans fats (or trans-unsaturated fatty acids). According to the Harvard Medical School:

The truth is, there never was any good evidence that using margarine instead of butter cut the chances of having a heart attack or developing heart disease. Making the switch was a well-intentioned guess, given that margarine had less saturated fat than butter, but it overlooked the dangers of trans fats.

Our understanding of cholesterol is now far more complex, with research looking at the effect of diet on “good” cholesterol (HDL or high-density lipids) and “bad” cholesterol (LDL or low-density lipids). Trans fats were shown to increase the bad and decrease the good cholesterol, leading margarine manufacturers to look hard at their processes. Most no longer contain much, if any, trans fat.

To complicate matters further, a research review published in 2015 seemed to show that reducing bad cholesterol had no effect or even a reverse effect on mortality rates. Others have pointed out that this study had serious flaws. So the safest bet is to replace what are charmingly called “yellow fats” with vegetable oils like olive oil. And to avoid fat-reduced foods that have had extra sugars and starches added to make them more palatable.

And how did Mo and Jo come up with the line “You oughta be congratulated” for Meadow Lea? It wasn’t just because the housewife was, in theory, opting for a healthier alternative. It was because, they said, there weren’t many words that rhymed with “polyunsaturated”.