Fat has been touted as one of the main culprits for obesity and a decline in health, but according to a new study, that isn’t necessarily the case. Unsaturated fats can, in fact, be beneficial to the human body and reduce mortality, a new study has found.

Saturated vs Unsaturated

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Fats come in two main categories: saturated and unsaturated. If you want to greatly simplify things (and please keep in mind, this is a gross simplification) unsaturated fats are “good fats,” and saturated fats are “bad fats.”

Saturated fats generally come from processed meat products such as sausages, ham or burgers. Hard cheeses and whole milk also contain saturated fats. Meanwhile, unsaturated fats come from vegetable oils, nuts and fish. It’s not that you should avoid saturated fats completely, but you should reduce and swap them for unsaturated fats.

However, for most people, fats get chalked up together and put in the “bad” corner. Researchers are trying to change that view.

Unsaturated is OK

In a large study which spanned over three decades, researchers from the Harvard T.H. Chan School of Public Health found that higher consumption of saturated and trans fats was linked with higher mortality compared with the same number of calories from carbohydrates. But more importantly,  replacing saturated fats with unsaturated fats conferred substantial health benefits.

Particularly, replacing lard and fat meat with olive oil and nuts provided numerous benefits to consumers.

“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, a doctoral candidate, SD ’16, in the Departments of Nutrition and Epidemiology at Harvard Chan School and lead author of the study. “This study documents important benefits of unsaturated fats, especially when they replace saturated and trans fats.”

Although it’s hard to quantify these effects and the figures should be taken with a grain of salt, scientists found that every 2% higher intake of trans fat was associated with a 16% higher chance of premature death during the study period. Carbohydrates had a similar, but less severe impact.

Conversely, the opposite was true for unsaturated fats. Both polyunsaturated and monounsaturated fats were associated with between 11% and 19% lower overall mortality compared with the same number of calories from carbohydrates. The findings are consistent with previous studies. The study included 126,233 participants.

“Our study shows the importance of eliminating trans fat and replacing saturated fat with unsaturated fats, including both omega-6 and omega-3 polyunsaturated fatty acids. In practice, this can be achieved by replacing animal fats with a variety of liquid vegetable oils,” said senior author Frank Hu, professor of nutrition and epidemiology at Harvard Chan School and professor of medicine at Harvard Medical School.

Journal Reference: “Specific Dietary Fats in Relation to Total and Cause-Specific Mortality,” Dong D. Wang, Yanping Li, Stephanie E. Chiuve, Meir J. Stampfer, JoAnn E. Manson, Eric B. Rimm, Walter C. Willett, and Frank B. Hu, JAMA Internal Medicine, online July 5, 2016, doi:10.1001/jamainternmed.2016.2417