There's no doubt--carbohydrates have taken center stage in public discourse about dietary practices. You can't turn on the TV, open a newspaper or walk past the office water cooler these days without hearing a debate about this nutrient du jour. Recently, however, increasing attention is being given to an all but forgotten part of our diet. Move over, carbohydrates: fat is making a comeback in the headlines. More specifically, trans fat.

Of the four types of dietary fat (monounsaturated, polyunsaturated, saturated and trans), the focus recently has been on trans fat. Abundant in margarine, shortening, packaged baked goods and French fries to name a few, trans fat is a widely used ingredient for food manufacturers because it is cheap and contributes to increased shelf life. It is listed as "partially hydrogenated vegetable oil" and "vegetable shortening" on product ingredient lists.

Hydrogenation is the process of heating an oil and passing hydrogen bubbles through it. The fat's density is increased, and food manufacturers use it frequently because it gives products a richer butter flavor. Saturated butter is much more expensive to use, so manufacturers reduce costs by using partially hydrogenated oils.

Partially hydrogenated oils, however, have a much different effect on the body than even the demonized saturated fats. We all know that we need to limit saturated fat in our diets, but specific amounts, although small, have been deemed acceptable, and even help to facilitate a variety of processes for the body. Trans fat, however, provides no positive effects whatsoever.

Studies have consistently shown that trans fat raises LDL (bad) cholesterol and lowers HDL (good) cholesterol. It contributes to clogging of the arteries and type 2 diabetes. Trans fat has also been linked to an estimated 30,000 or more premature heart disease deaths each year.

In March 2004, the Food and Drug Administration updated their website pages concerning trans fat and regulations concerning labeling laws. Although the FDA first proposed trans fat labeling in 1999, it wasn't until July 2003 that Health and Human Services Secretary Tommy Thompson announced the new trans fat ruling. Even then, the guidelines proved to be less than acceptable to health experts who were pushing for immediate regulations: the ruling gave manufacturers until January 1, 2006 to comply.

Some food manufacturers, however, have already started listing the ingredient on their nutritional labels, and the FDA has responded to these changes for consumers with trans fat info and guidance to understanding the new labels. See the FDA website at http://www.cfsan.fda.gov/~dms/transfat.html#unhide).

Issues of further contention exist, most notably because the FDA is choosing not to list a % Daily Value (%DV) for trans fat. Although it admits that scientific reports show a link between trans fat and coronary heart disease, the FDA states that none of these studies have provided a specific reference value. This has enraged anti-trans fat advocates, who consider the decision not to list daily values a cop-out due to pressure from the food industry, not to insufficient evidence of harm (check out http://bantransfats.com/ for a comprehensive and excellent review of the latest trans fat advocacy issues).

Unlike the FDA's specific daily requirements for both saturated fat and cholesterol already in place, some experts feel this lack of specificity for trans fat allotment in our diet is akin to allowing the consumer to believe that any amount is acceptable. Thus, the possibility of a veritable free-for-all on trans fat consumption is feared.

The race is now on for food manufacturers to produce foods free of trans fat

In April 2004, Kraft Foods announced the introduction of three new brands of the popular Oreo cookie containing zero grams of trans fat. Other manufactures will surely follow suit and it is likely that we will be seeing an explosion of trans fat-free (although not necessarily nutritious) products, particularly snack foods.

Since we have a while to wait until all manufacturers are required to change their product labels, consumers need to know how to recognize trans fat in products to reduce intake. Read every ingredient label before a product is purchased. If the list contains the words "partially hydrogenated," you know it contains trans fat. Shortening and margarine almost always contain trans fat. This knowledge is particularly important with regard to processed foods, since they usually contain a large amount of ingredients, most with long, odd looking and hard to pronounce names. For further guidance on how to avoid trans fat in products, check out Dr. Gabe Mirkin's website (http://www.drmirkin.com/nutrition/N185.html), an excellent resource on nutrition and trans fat info.

Conflicting as it may be, we'll always be inundated with media attention on the latest focus on nutrition. But we still need to be aware of the facts concerning our health. Coverage on fats was all the rage in the 80's, for the last decade all we've heard about is carbs. What's next? Well, there's always protein.