I read somewhere that frying foods in general arent healthy because when you fry oils that dont contain transfats at very higih temp. they can produce transfats,, in fact, in this article on atkins, it states the same thing:

http://atkins.com/Archive/2003/7/14-379496.html

So how do we justify frying foods?

I stir-fry lots of items, but I don't deep fry anything. I read somewhere that frying with oil once is OK, but reusing it again and again is when the transfats really become a problem.

Negative. Creating trans fats is a patented process. You need to heat vegetable oil in the presence of hydrogen and a metal catalyst to create hydrogenated oil. Hopefully you aren't cooking that way

Here is how trans fats are created, courtesy of Weston Price:

Hydrogenation: This is the process that turns polyunsaturates, normally liquid at room temperature, into fats that are solid at room temperature—margarine and shortening. To produce them, manufacturers begin with the cheapest oils—soy, corn, cottonseed or canola, already rancid from the extraction process—and mix them with tiny metal particles—usually nickel oxide. The oil with its nickel catalyst is then subjected to hydrogen gas in a high-pressure, high-temperature reactor. Next, soap-like emulsifiers and starch are squeezed into the mixture to give it a better consistency; the oil is yet again subjected to high temperatures when it is steam-cleaned. This removes its unpleasant odor. Margarine’s natural color, an unappetizing grey, is removed by bleach. Dyes and strong flavors must then be added to make it resemble butter. Finally, the mixture is compressed and packaged in blocks or tubs and sold as a health food. (Margarine)

Here's the worst part about the manufactured Trans fats, again courtesy of Weston Price:

Partially hydrogenated margarines and shortenings are even worse for you than the highly refined vegetable oils from which they are made because of chemical changes that occur during the hydrogenation process. Under high temperatures, the nickel catalyst causes the hydrogen atoms to change position on the fatty acid chain. Before hydrogenation, pairs of hydrogen atoms occur together on the chain, causing the chain to bend slightly and creating a concentration of electrons at the site of the double bond. This is called the cis formation, the configuration most commonly found in nature. With hydrogenation, one hydrogen atom of the pair is moved to the other side so that the molecule straightens. This is called the trans formation, rarely found in nature. Most of these man-made trans fats are toxins to the body, but unfortunately your digestive system does not recognize them as such. Instead of being eliminated, trans fats are incorporated into cell membranes as if they were cis fats—your cells actually become partially hydrogenated! Once in place, trans fatty acids with their misplaced hydrogen atoms wreak havoc in cell metabolism because chemical reactions can only take place when electrons in the cell membranes are in certain arrangements or patterns, which the hydrogenation process has disturbed.

I think the temperatures required are insanely high. If you're like some of these TV Chefs who sear everything at 80 Gazillion Degrees, it might be a problem. But, I don't think the average temperatures you reach while Frying or Roasting will create a problem. Frying temps range from 265-375 and Roasting temps from 170-350 degrees. Baking temperatures are too high though IMHO...They range from 375-500...I suggest using the low end. For example, one recipe I tried sometime back called for a oven temperature of 450 degrees. I followed the directions to the letter and ended up with a Pastry with a burnt taste. I tried it again, lowering the temperature to 375-400...and got a much better tasting Pastry.

The above comments on the creation of transfats are absolutely correct. However many oils break down from REPEATED use and form free radicals which are also a health hazard. Unless you are using animal fats or saturated vegetable fats, such as coconut oil, cooking oils should be discarded after 1 or 2 uses. Nyah Levi

I cook with Coconut Oil, Palm Oil, and/or Lard...So, I don't worry too much about the oil breaking down. Lard is $0.75/lb...so, throwing it out after 1 use is no Big Deal. Palm Oil is $5.17/lb and Coconut Oil is $6.27/lb, so I reuse them whenever possible.

Below 375 works for 90% of oils. Some can take higher temperatures, and a few can't handle 375.

http://www.goodeatsfanpage.com/Coll...SmokePoints.htm

According to this page Coconut Oil has a Smoke Point of 350F. But, according to one manufacturer of Virgin Coconut Oil it is 198C, which is 388F. I can't seem to find a smoke point for Refined Palm Oil or Refined Coconut Oil. But, Hydrogenated Palm Oil is 428 and Winterized (Dry Fractionated) Palm Oil is 425. Unfortunately, the compositions of these two vary considerably (Hydrogenated Palm Oil is 49% Saturated and 51% Trans, while Winterized claims to be only 6% Saturated) from that of Regular Palm Oil (49% Saturated, 37% Monounsaturated, and 9% Polyunsaturated), so these numbers are of no use. As for Canola, it has a smoke point of 225, 350, or 400 depending on the level of Refinement. The more refined, the higher.

When I cook a roast, I keep the temperature between 325 and 350, unless I'm slow roasting...Then, I'll use a temperature as low as 170-200. For Baking, I use about 350-400. I get good results with these temperatures.