THURSDAY, July 12, 2001 (HealthDayNews) -- Remember when wolfing down a big plate of fries at the drive-in went from fun to frightful? It started when scientists discovered the heart-related dangers of foods soaked in saturated fats, including animal-based fats like lard and palm and coconut oils. They said the solution was to cook those fries (or doughnuts or cookies or pies) with trans fat, better known as hydrogenated vegetable oil.
Well, hold onto your junk food coupons, campers: A study reported today by the American Heart Association says foods cooked with trans fats may be more harmful to your blood vessels than those cooked in old-fashioned saturated fat.
But before you celebrate, here's the rub: Neither fat is good for you.
"It not so much that we should be deciding to choose one fat over another. The real message in this study is the need to reduce our intake of both trans fats and saturated fats," says Cindy Moore, director of Nutrition Therapy for The Cleveland Clinic Foundation and a spokeswoman for the American Dietetic Association.
The goal of the research was "to compare saturated fats with trans fats because of [their potential] to affect HDL levels," says lead study author Nicole DeRoos of Wageningen University in the Netherlands. HDL, or high density lipoprotein, is the "good" cholesterol that helps prevent heart disease.
DeRoos say the research showed that trans fats reduced blood vessel function nearly one-third more than saturated, lard-like fats, and they reduced HDL cholesterol levels up to one-fifth more than saturated fats, increasing the risk of heart disease.
DeRoos says the nasty effects are partly the result of the hydrogenation process that infuses substances like corn or soybean oil with a hydrogen atom, turning liquid oils to solid fats at room temperature. Trans fat, called "hydrogenated" or "partially hydrogenated" oils, are listed on the label of your favorite cookies, cakes or pies.
While the negative effects of trans fats may be new to most folks, the finding is no surprise to Moore and other nutrition experts.
"I think this demonstrates the ongoing recommendation of the American Heart Association and others that we need to limit the amount of saturated fats as well as trans fatty acids in our diet to no more than 10 percent of our total fat intake," says Moore.
She says the rest of our fat intake, which should amount to no more than 35 percent of our total dietary calories, should come from mono- or polyunsaturated fats, like olive or canola oils in their natural, liquid state.
"The chemical structure of these fats are different, and they do not have the negative impact on our health as do the other fats. In fact, they can be good for us," says Moore.
The new study, known as a crossover dietary trial, involved 29 healthy men and women who ate the same diet with one exception: One group ate margarine made from partially hydrogenated soybean oil (a trans fat), while the other group ate margarine made from palm kernel oil (a saturated fat). The levels of fats for both groups was kept below 10 percent of their total caloric intakes.
After four weeks on one diet, the patients switched margarines, so all 29 got to sample both products during the eight-week study.
Researchers measured artery dilation in the arm of each participant at the start, middle and end point of each portion of the trial.
The result appear in the latest issue of the journal Atherosclerosis, Thrombosis and Vascular Biology.
While margarine was the fat source used in both diets, before you reach for that buttered croissant, DeRoos warns: "Margarines are not the main source of trans fatty acids in our diet. Ready-made foods such as French fries, doughnuts and crackers are the main source, and low-fat margarines rich in polyunsaturated fat and low in saturated fats are still a healthier alternative than butter."
What To Do
For more about fat content in foods and for some low-fat recipes, check Delicious Decisions, the American Heart Associations dietary advice site.
You can also get dietary advice and the latest news about dietary fats from the American Dietetic Association.
For information on how to find the fat on food labels, visit the Food and Drug Administration's Center for Food Safety and Applied Nutrition. And for a breakdown of fat, vitamins, calories and other nutrients, check the Interactive Healthy Eating Index.
