but about every ingrident label ive seen contains partially hydrogenated oil...even the "healthy foods"
Guess what. They're not really as healthful as they claim, then, are they?
Just a general word of advice, stick to non-processed foods. You'll quickly discover that they have much lower glycemic indexes and generally lack the problem ingredients food manufacturers use to make their products more appealing. And yes, partially hydrogenated corn syrup is one of the worst "foods" you can dump into your body. And yes, it's in everything. Stick with the non-processed food.
To answer your first question, transfatty acids are fats that have been hydrogenated. In an unsaturated fat molecule, the lipid chains trailing the carboxylic acid head have double bonds in them. They tend to be liquids at room temerature, as the double bonds form kinks and prevent them from weakly bonding with other fatty acids. Saturated fats don't have any double bonds, and hence are solid at room temperature.
Well, as it became the trend to cook with healthier oils (as opposed to lard, etc...), it was found that the unsaturated oils became unstable over time and quickly went rancid. So in order to maintain shelf-life, unsaturated oils were hydrogenated to prevent oxidation. Some of these hydrogen molecules would be lost, but the normal orientation of the double bond would be changed (thus trans fats). (The end and desired result is also that these unstable oils would become more solidified and stable.)
Basically, trans fatty acids behave a lot like saturated fats. They elevate LDL ("bad" cholesterol) and also lower HDL ("good "cholesterol) levels. Why does this happen? Well, when your body converts saturated fats into cholesterol, saturated fats are converted to trans fatty acids along the way. Thus, the trans fats just jump right into your biological pathway and are converted into LDL cholesterol.
Avoid them just as you would avoid saturated fats.