Butter might be better.
Since the 1960s, consumers have been told to swap butter and other saturated fats with “heart healthy” options like vegetable oils high in linoleic acid.
Now a re-examination of previously unpublished data from the study that first made that claim is casting doubt.
Researchers at the University of North Carolina School of Medicine and the U.S. National Institute for Health recently reviewed the Minnesota Coronary Experiment, conducted between 1968 and 1973.
It shows high-linoleic acid oils do reduce cholesterol levels, but fail to deliver on other promised health benefits.
In fact greater cholesterol reduction had higher not lower risk of death.
“Incomplete publication of important data has contributed to the overestimation of benefits and the underestimation of potential risks,” said Daisy Zamora, a researcher at UNC and one of the authors of the paper, published Apr. 12 in the British Medical Journal.
The original researchers found replacing saturated fats with vegetable oils lowers blood cholesterol and later studies linked this to reduced heart attack risk.
In 2009, the American Heart Association reaffirmed its view that a diet low in saturated fat and moderately high amounts of linoleic acid and other omega-6 unsaturated fatty acids probably benefits the heart.
However, randomized controlled trials — considered the gold standard for medical research — have never shown the link.
Why linoleic acid-containing oils would lower cholesterol but worsen or fail to reduce heart attack risk is the subject of debate. Some studies suggest that these oils can sometimes cause inflammation, a risk factor for heart disease. There is also some evidence they can promote atherosclerosis.