The Harvard-led meta-analysis, reports that people who swap just 5% of calories from foods high in saturated fat to those that are high in linoleic acid — the main polyunsaturated fat found in vegetable oil, nuts, and seeds— have 9% lower risk of coronary heart disease (CHD) events and a 13% reduction in the risk of death from CHD.
Published in Circulation, the data from the Harvard School of Public Health (HSPH) also revealed that substitution of 5% of calories from carbohydrate with linoleic acid was also associated with similar reductions in risk of heart disease.
"There has been much confusion and sensational headlines about the role of different types of fat in CHD," said senior author Professor Frank Hu. "Randomised clinical trials have shown that replacing saturated fat with polyunsaturated fat reduces total and LDL cholesterol.”
“Our comprehensive meta-analysis provides clear evidence to support the benefits of consuming polyunsaturated fat as a replacement for saturated fat,” he stated.
Analysing the evidence
Hu and his colleagues performed a systematic review and meta-analysis of prospective cohort studies to summarise the evidence for a link between dietary linoleic acid intake and CHD risk in generally healthy people. They identified 13 published and unpublished cohort studies with a total of 310,602 individuals and 12,479 total CHD events including 5,882 CHD deaths.
Results showed that dietary linoleic acid intake is inversely associated with CHD risk in a dose-response manner—meaning higher intakes of linoleic acid resulted in a lower risk of CHD.
“A 5% of energy increment in LA intake replacing energy from saturated fat intake was associated with a 9% lower risk of CHD events and a 13% lower risk of CHD deaths,” wrote the Harvard researchers.
Comparing the highest to the lowest level of consumption, dietary linoleic acid was associated with a 15% lower risk of CHD events and a 21% lower risk of CHD deaths.
These results were independent of common coronary heart disease risk factors like smoking and other dietary factors such as fibre consumption, said the team.
In practice, Hu and his team said the findings support replacing butter, lard, and fat from red meat with liquid plant oils in cooking and at the table.
“These data provide support for current recommendations to replace saturated fat with polyunsaturated fat for primary prevention of CHD,” they concluded.
Volume 130, Pages 1568-1578, doi: 10.1161/CIRCULATIONAHA.114.010236
“Dietary Linoleic Acid and Risk of Coronary Heart Disease: A Systematic Review and Meta-Analysis of Prospective Cohort Studies”
Authors: Maryam S. Farvid, Ming Ding, et al