When buying margarine, opt for the trans-free tub or liquid kinds. The more solid a margarine is at room temperature, the more trans fat it contains.

Margarine contains trans fatty acids which are more dangerous than saturated fat. Trans fat are formed when hydrogen is added to vegetable oil through a process called hydrogenation. This makes the fat more solid and less likely to spoil. Trans fat can increase the risk of coronary heart disease by raising levels of LDL cholesterol ("bad" cholesterol) and lowering levels of HDL cholesterol ("good" cholesterol). Health authorities worldwide recommend that consumption of trans fat be reduced to trace amounts.

American Heart Association (AHA), National Heart, Lung and Blood Institute (NJLBI) and the National Cholesterol Education Program (NCEP) recommend the trans-free tub or liquid kinds margarine fortified with Vitamin A and D. Plant sterol esters or plant stanol esters have been added to some margarines and spreads because of their cholesterol lowering effect.