Margarine is the result of vegetable oil put through a hydrogenation process which creates a solid substance, in essence spreadable fat. While it has been marketed as a healthier butter substitute, margarine is so full of trans fats that even minimal consumption could increase your risk of heart disease.
The most harmful aspect of consuming margarine is chronic inflammation - linked to Rheumatoid arthritis, Scleroderma, Systemic lupus and of course heart disease. Chronic inflammation has dietary roots and could be triggered by any diet involving dairy products.
While consumption peaked in 1993, United States citizens nowadays eat about 2 billion pounds of margarine per year. The margarine and cooking oil industry legally sold $4.2 billion worth of buttery spreads in 2011 and not one customer was fined or imprisoned from consuming this harmful substance.