Findings published in the JAMA Internal Medicine suggest that replacing saturated fats with unsaturated fats from plant-based foods—like olive oil, canola oil and soybean oil — can offer significant health benefits.
The results also suggest a higher consumption of saturated and trans fats correlated with a higher death rate when compared with an equivalent number of calories from carbohydrates.
The team found a 2% higher intake of trans fat translated into a 16% higher chance of early death during the study period.
When likened with the same number of calories from carbohydrate, a 5% increase in saturated fat intake corresponded to an 8% higher death rate.
In contrast, consuming high amounts of polyunsaturated and monounsaturated fats translated into a lower overall rate of death of between 11% and 19%. These values were compiled when compared with an equal number of calories from carbohydrates.
This research provides further confirmation for the European Food-Based Dietary Guidelines set out by the World Health Organization (WHO) that recommend less than 10% of daily energy intake come from saturated fat.
These guidelines also recommend replacing saturated fats with unsaturated vegetable oils or soft margarines.
In total 126,233 subjects were gathered from two studies —the Nurses’ Health Study (83,349 women from 1980 to 2012) and the Health Professionals Follow-Up Study (42,884 men from 1986 to 2012).
These subjects were questioned on their dietary fat intake at the beginning of the study and updated every two to four years for up to 32 years
During the follow-up, 33,304 deaths were recorded by the team from Harvard Chan School and Brigham and Women’s Hospital.
The circumstances surrounding their death were then examined, focusing on the link between types of fats in the subjects’’ diets and overall deaths, particularly those attributed to cardiovascular disease (CVD), cancer, neurodegenerative disease and respiratory disease.
“There has been widespread confusion in the biomedical community and the general public in the last couple of years about the health effects of specific types of fat in the diet,” said Dong Wang, lead author of the study and doctoral candidate at Harvard Chan School.
“This study documents important benefits of unsaturated fats, especially when they replace saturated and trans fats.”
The findings for CVD go along with previous research that demonstrates reduced total and LDL ('bad') cholesterol when trans or saturated fats are substituted for unsaturated fats.
Individuals who substituted saturated fats with carbohydrates were found to have a slightly lower risk of death. The team also found that substituting total fat with carbohydrates was linked with small increase in the death rate.
“This was not surprising,” the authors said, “because carbohydrates in the diet tend to be primarily refined starch and sugar, which have a similar influence on mortality risk as saturated fats.”
Dr Gunter Kuhnle, associate professor in Nutrition and Health, University of Reading, said that there was much public discussion about dietary guidelines recently, especially a call to end the demonisation of fat (and to demonise carbohydrates instead).
“This approach is dangerous as it not only confuses the public, but also discourages the public from following sound recommendations,” he said.
“This study has an important limitation. While the current study does distinguish between different types of saturated and unsaturated fats, this is still not detailed enough.”
“The current study also relies on self-reported data for diet, which is likely to introduce bias and does not provide the same level of detail than more objective methods.”
Source: JAMA Internal Medicine
Published online ahead of print, doi:10.1001/jamainternmed.2016.2417
“Association of Specific Dietary Fats With Total and Cause-Specific Mortality.”
Authors: Dong Wang et al.