The dangerous Trans Fat

Foods that usually contain high levels of trans fats:

Pastries and cakes
French fries (unless fried in lard / dripping)
Doughnuts
Cookies / biscuits
Chocolate
Margerine
Shortening
Fried chicken
Crackers
Potato chips

Trans fats

Many of the random compounds created when oils are hydrogenated are so-called "trans fats" or, more correctly, trans-fatty acids. These are unnatural compounds, which are known to be detrimental to health. In order to understand why, we need to consider some of the chemistry involved. (not too much, I promise).