Trans fats are found in partially hydrogenated and hydrogenated oils - often used in margarine, as well as pastries, processed, and deep-fried foods.
Because these oils can be synthetically produced, they are cheap and help increase the shelf-life of the processed foods you see in the supermarket.
One study in pregnant women suggested that when dietary fat was kept at 30% of total calories, 90% of trans fat intake came from bakery items, while 10% came from table spreads such as margarine (11). If you reduce (preferably eliminate) processed foods, pastries, donuts and the like, you can significantly reduce your intake of these harmful fats.
I support the principle of “out of sight, out of mind”, if I don’t go past the items at the grocery store, and I don’t let them into my house, then they will not find their way into my mouth.
Dietary trans fatty acids are dangerous because they lower levels of “good” HDL cholesterol and raise levels of “bad” LDL cholesterol - and are associated with a higher incidence of heart attack and stroke (2; 3; 4; 5; 6; 7; 8).
Additionally, trans fats have been implicated in inflammation, insulin resistance, diabetes, and excess weight gain (9).
In 2003, the FDA mandated that trans fat content be labeled on foods in response to a push by researchers such as Mary Enig, PhD and Walter Willet, PhD who have warned about trans fats for years (10).
In comparison, education against trans fats was vastly outweighed by the half a century lobbying effort against short, medium, and long-chain saturated fats - fueled first by the soybean lobby, and later by the pharmaceutical industry. Even though nutrition pioneers like Dr. Enig scored a victory with the labeling mandate, the food industry was still able to list 0g trans fat on nutrition labels if the product contained less than 2g per serving. Compromises like these are often seen with regulation as industry lobbyists still run amok in Washington. This was confusing for consumers, as a package could say 0g of trans fat, but still contain partially hydrogenated and hydrogenated oils.
A May 2013 review, the European Journal of Nutrition concluded, “...the detrimental effects of industrial trans fatty acids on heart health are beyond dispute” (11).The only controversy that really existed was whether or not we would force companies to use more expensive ingredients in the name of health.
While it has taken over a decade for the education against trans fats to spread, finally the Food and Drug Administration is moving to ban trans fats completely from the food supply - a big victory for consumers as heart disease still attributes to some 50% of deaths in the United States.