We've just come off several years of hearing that trans fat is bad for us -- worse than lard, worse than butter, worse than eating pork rinds and bacon grease.
And now they're telling us there's good trans fat?
That bites, you say.
Indeed, trans fat has become the whipping post of the entire health community, because it raises the bad (LDL) cholesterol -- just as too much saturated fat does -- but it has a double-whammy effect of lowering the good cholesterol (the HDL stuff) too.
There was finally one point on which virtually every health and medical professional could agree: Let's get the trans fat out of our food!
The government heard the evidence loud and clear, and kind of took steps in that direction.
Rather than ban trans fat altogether, the government required manufacturers to list the trans fat content on their nutritional labels as of Jan. 1, 2006. Fully aware that having trans fat on the nutrition panel would be the equivalent of box office poison for any food, manufacturers scrambled to reformulate their products so that their labels could say "0 grams of trans fat."
That doesn't mean the product has no trans fat, though, because there's a tiny loophole in the regulations. The food can still have added trans fat, but if it amounts to less than half a gram per serving, the label can round it down and say "0 grams trans fat." Of course, eat a few servings of the stuff, which Americans tend to do, and you've potentially eaten a couple of grams of trans.
The trans fat you've heard about is a manufactured or industrial trans fat. It starts out as liquid vegetable oil, which then gets bombarded with hydrogen atoms to make it a bit more firm at room temperature.
In this form, it's called "partially hydrogenated vegetable oil," and too much of it is what has bad effects on our cholesterol levels.
Interestingly, if the vegetable oil is "fully hydrogenated," then it's not "trans" anymore, and it just becomes another saturated fat.
Manufactured trans fat is found mostly in baked goods like pastries, cookies, cake, as well as those ever-lovin' french fries and other deep-fried foods like fried chicken. It's also in some brands of vegetable shortening, although it's now being removed from most of them.
As a baking ingredient, this partially hydrogenated stuff replaced butter decades ago. Manufacturers liked it because it had less saturated fat and no cholesterol, so it was thought to be healthier. Besides, it was a heck of a lot cheaper than butter, so manufacturers figured it was a win-win.
Now, because of evolving scientific evidence, they've done an 180-degree turn. And today they can't get trans fat out of the food supply fast enough.
In addition to the manufactured type of trans fat, natural trans fats can also be present, mostly in meat and dairy foods. But it's not quite the same as the partially hydrogenated stuff. Natural trans fats might even be good for you.
One such natural trans fat is called conjugated linoleic acid, or CLA. It's present mostly in meat and dairy foods, such as milk, yogurt and cheese.
Preliminary research suggests that its benefits may include actually reducing the risk of certain cancers and heart disease. A review of clinical research over the past 16 years, published recently in the journal Lipid Technology, stated that natural CLA trans fat "has no effect or may actually lower LDL cholesterol and has little effect on HDL cholesterol or triglycerides."
But consuming the manufactured variety of trans fat likely trumps out the good stuff for most people.
If you're like the average person in the United States, you're getting about 2 to 3 percent of your calories from manufactured trans fat. That would be about 4 to 6 grams (amounting to 36 to 54 calories) for a 2,000-calorie diet.
Another recent review in the journal Lipids concluded that one would need to eat 4 percent of your total calories as manufactured trans fat to raise your bad cholesterol, and about 6 percent to lower your good cholesterol.
That said, this level is quite possible if you regularly eat a lot of fries, baked goods and deep-fried foods. Think about it -- a nice order of fries and a few cookies for a kid, and he's over the limit. Definitely doable.
Manufacturers are quickly finding substitutes for manufactured trans fat, but we're not out of the woods yet.
The thing is, the best substitute for partially hydrogenated fat in food is either butter or some other saturated fat. Why? Two reasons.
First, with baked goods, you need a fat that will remain solid at room temperature. Make a batch of cookies with corn oil and they'll drip like a faucet when they cool off.
Second, for deep-frying, solid fats have a higher smoking point, so there's less risk of them bursting into flames at frying temperature.
The good news is that some things are already being done for you.
Whether they sell deep-fried foods or packaged baked goods, most companies are switching to trans-free fats, even if that means they're likely just trading manufactured trans fat for saturated fat.
As for the natural trans fats, like CLA, there seems to be no need to worry about them, at least not at this point, and they may even bring some benefits.
Here are some simple tips to keep your dietary "trans action" in check:
Eat deep-fried foods only occasionally (hint: occasionally is not every other day but more like once a week -- at most) and in modest portions.
Read the nutrition facts panel on packaged goods. Aim for foods that say "0 grams trans fat."
Read the ingredient label also. If it says "partially hydrogenated vegetable oil," at least make sure that the nutrition facts label says "0 grams trans fat."
Keep to single portions of baked goods; these foods are not usually overflowing with nutrition, so keep them as occasional foods either way.
As for natural trans sources, don't sweat over them. Dairy foods such as milk, yogurt and cheese are nutrient-rich, loaded with calcium and lots of other nutrients we need. They can also be high in saturated fat however, so get lower-fat choices most of the time. How much cheese? Keep it to about four ounces a week. That's livable, will keep you happy, and can still keep your diet low in saturated fat.
Keith-Thomas Ayoob is an associate professor in the department of pediatrics at the Albert Einstein College of Medicine in New York City.