That old standby about tucking into a pint of ice cream to get over a breakup? Counterproductive, according to a large new study that finds a link between eating trans fats and an increased risk of depression.
For the study, researchers in Spain tracked the dietary habits, lifestyles and mental health of 12,059 college graduates (average age 37.5) for six years. None of the participants had depression at the start of the study; by the end, researchers had identified 657 new cases, which were self-reported by the participants in questionnaires filled out every two years. (More on Time.com: 5 Better-For-You Morning Meals)
Researchers found that the risk of developing depression increased as trans-fat consumption rose. Those in the highest quintile of trans-fat intake — deriving at least 0.6% of their daily calories from trans fats — had a 42% increased risk of depression, compared with those in the lowest consumption group, who barely ate any trans fats at all.
The study also found that people who ate a lot of monounsaturated and polyunsaturated fats, like those found in olive oil, had a lower risk of depression — but that association diminished when researchers controlled for other dietary factors such as adherence to the Mediterranean diet.
The data were collected as part of the “Seguimiento Universidad de Navarra” (SUN) Project — a long-term cohort study modeled after the long-running Nurses’ Health Study, funded by the U.S. government. (More on Time.com: Can a Veggie-Rich Diet Make You More Beautiful?)
The results of the study may be especially bad news for Americans. While the average Spaniard gets about 0.4% of his or her calories from trans fats — mostly from natural or whole-food sources like milk, butter, meat and cheese — Americans log an average of 2.5% of total calories from trans fats. Americans not only eat more overall, but also eat worse-quality food, getting many trans fats from sources like processed snack foods and fried or fast food.
The authors also note that high trans-fat intake is a known risk factor for cardiovascular disease, and that many people with cardiovascular disease are depressed; the two conditions may share a common underlying pathway. Reported the Los Angeles Times:
In countries where the average intake of trans fats is high, such as the United States, the contribution of the bad fats to depression may be even stronger, said the researchers, from the universities of Navarra and Las Palmas de Gran Canaria.
Many people with heart disease also have depression, the authors noted. It could be that trans fats contribute to both disorders through a similar mechanism. Bad fat increases inflammation in the body. In the heart, that contributes to the buildup of plaque that can cause heart disease. In the brain, substances secreted by inflammation may interfere with neurotransmitters that affect mood.
The study can’t say definitively whether eating trans fats contributed to depression, or whether people who were predisposed to depression ate poorer quality diets. But the authors excluded cases of depression that were diagnosed during the first two years of the study, which strengthened the association. (More on Time.com: 10 New Diet Books for 2011)
“When you exclude the early cases you can be pretty sure the cases occurring after four, five years were not present at the beginning,” study author Miguel Angel Martinez-Gonzalez told the National Post, suggesting that, “First it’s the trans fat, then it’s the depression.”
So while devouring a carton of chocolate ice cream might make you feel good in the moment, you may just be trading short-term pleasure for a longer-term increased risk of depression.
The new study was published by the journal PLoS One.
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