One of the key markers of a highly-processed diet is trans-fatty acids, or trans fats. These abnormal fats are a result of either deep frying or a process called hydrogenation, which is used to extend the shelf life of packaged foods. Doughnuts, cookies, crackers, French fries, or almost any fried fast food are rich sources of this insidious killer.
Numerous studies in recent years have found that these are more of a culprit in raising the risk of heart disease, stroke, and diabetes than the oft-maligned saturated fats. Recently, researchers have found that trans fats have an impact on mood and behavior as well. Spanish researchers in 2011 found a direct relationship between intake of trans fats and risk of depression. On the flip-side, consuming monounsaturated fats (such as olive oil and avocados), or polyunsaturated fats (such as fish oil, nuts, and seeds) decreased depression risk.
Just a few months ago, researchers at the University of California San Diego found that higher trans fat intake is associated with increased aggression and irritability. And once again, the polyunsaturated fats correlated with increased agreeableness and reduced impulsivity. While this doesn’t prove that trans fats cause increased aggression, it just adds to the mountain of evidence for avoiding this toxic ingredient.
One caveat: trans fats are harmful in and of themselves, but they are also a marker for highly processed foods. And one thing that American food manufacturers are good at is manipulating processed foods to follow the latest trends in nutritional awareness — just look at the labels touting “Trans Fat Free,” “Low-Carb,” “Low-Sodium,” etc. Your best bet is to stick as much as possible to real, whole foods — foods as close to their natural plant or animal source as possible.