People who eat more trans fats from cheese, milk or processed foods may have a 48 percent increased risk of depression, compared with those who consume almost no trans fats, a study from Spain showed.
Olive oil, by contrast, appeared to have a slight protective effect against the mental illness among 12,059 Spanish participants in the research, according to a report in the journal PLoS One.
The study is the first to analyze the effects of dietary fat on depression, the authors wrote. Research has already linked trans fats, which are created through a process that adds hydrogen to oil, to increased heart risk.
“Our findings suggest that trans fat intake, a well known risk factor for cardiovascular disease, might also have a detrimental effect on depression,” wrote the authors, who were led by Almudena Sanchez-Villegas, a researcher at the University of Las Palmas de Gran Canaria in Spain.
The effects of trans fats on mood may be more amplified in a study of Americans, who eat more processed foods, a major source of trans fats, the authors wrote. In the Spanish study, most of the trans fats came from milk and cheese, and contributed only 0.4 percent of total energy. In an American diet, about 2.5 percent of energy intake is trans fat, mostly from artificial foods, the authors wrote.
The 48 percent increase in depression risk was found among those whose diet consisted of more than 0.6 percent of calories from trans fats, compared with almost no trans fats.
Trans-fat and overall dietary intake were measured by a 136-item food questionnaire filled out by study participants that the authors said showed validity for assessing fat content. Nutrient amounts were calculated using the latest available information from food composition tables for Spain, they said. The questionnaires were given at the beginning of the study and again a second time, then analyzed.
The authors suggest that depression may be related to low-grade inflammation, which is commonly observed in patients with depression. Trans fats increase inflammation, which is also a risk factor for cardiovascular disease, as well as raising bad cholesterol and lowering good cholesterol, the authors wrote.
Olive oil contains some chemicals that have anti-inflammatory properties, which may help the circulatory system function better, the authors wrote. People who ate olive oil were less likely to be depressed, the study found. This association wasn’t significant once the researchers adjusted for people who ate a Mediterranean diet, one rich in fish, fruit, and vegetables.
About 150 million people worldwide are depressed, according to background information in the study.
The study was funded by the Spanish government’s Instituto de Salud Carlos III and the regional government of Navarra, Spain.