These were the preliminary results of an analysis of two large studies that collected information from more than 93,000 men and women over an average of 22 years.
The research — which was led by the Harvard T.H. Chan School of Public Health in Boston, MA — featured at the American Heart Association’s 2018 scientific sessions on Epidemiology and Prevention | Lifestyle and Cardiometabolic Health, held in New Orleans, LA.
You can read an abstract on the study in the journal Circulation.
Monounsaturated fats are unsaturated fats that have only one carbon-carbon double bond in their hydrocarbon backbone. At room temperature, they usually remain liquid and only become solid when refrigerated.
There are two sources of monounsaturated fat in the human diet: plant foods such as avocados, nuts, peanut butter, olive oil, sesame oil, and other vegetable oils; and animal foods, including red meat, fish, eggs, and full-fat dairy products.
Guidelines in the United States recommend that no more than 30 percent of the calories in our diet should come from fats, most of which should be monounsaturated or polyunsaturated.
Detailed information about food sources
Dr. Marta Guasch-Ferré, who is a research associate in the Department of Nutrition at the Harvard T.H. Chan School of Public Health, and colleagues carried out their study because previous research about monounsaturated fats and mortality has yielded inconsistent results.
Because monounsaturated fats are present in both animal- and plant-based foods — and contain “divergent nutrient components” — they decided to investigate whether the source of the fats might be significant or not.
They combined and analyzed data from two studies. One dataset was collected in 1990–2012 from 63,412 females in the Nurses’ Health Study. The other dataset, which was drawn from the Health Professionals Follow-Up Study, included data collected in 1990–2010 on 29,966 males.
The records from these studies had detailed, validated information about diet that was collected every 4 years from food frequency questionnaires filled in by the participants.
From these records, and by consulting scientific sources to note changes in food composition that might have occurred over the follow-up, the researchers were able to calculate and differentiate among the different fat types in the participants’ diets, the food sources they came from, and exactly how they changed over time.
Plant-based fats tied to lower risk of death
Over an average follow-up period of 22 years, 20,672 of the subjects died — including 4,588 from heart disease. Using this information and that of fat consumption, the researchers found that:
- Having a diet higher in plant-based monounsaturated fats was linked to a 16 percent lower risk of dying from any cause over the follow-up compared with having a diet that was low in these fats.
- Replacing 2–5 percent of calories derived from saturated fats, simple sugars, and other refined carbohydrates with the same amount of calories from plant-based monounsaturated fats was linked to a 10–15 percent lower risk of death from heart disease and any other cause.
- Substituting 5 percent of total calories sourced from animal-based monounsaturated fats with plant-based ones was tied to 24–26 percent lower risk of death from heart disease and any other cause.
It should be noted that these results came from an analysis of observational data that is only able to determine links between types of monounsaturated fats and risk of death.
Therefore, while the findings do not actually prove that eating plant-based monounsaturated fats — as opposed to animal-based ones — reduces the risk of premature death, they do not contradict that assertion.
“Our results emphasize the importance of the source and quantity of monounsaturated fatty acids in the diet — we should eat more monounsaturated fatty acids from plant sources and less monounsaturated fatty acids from animal sources.”
Dr. Marta Guasch-Ferré
The study was part-funded by Unilever, and three of the seven study authors disclosed either being in receipt of a research grant or being employed by the company. Unilever own many well-known household brands, including some food products based on plant oils.