Trans-fat increase cholesterol levels
Maggie Fox, Reuters, Washington
Fats found in meat, milk, cookies and fries raise cholesterol, U.S. government advisers say, but they have decided not to set limits because it would be too hard for people to meet them.
Because trans-fatty acids always raise cholesterol, especially "bad" or LDL cholesterol, people should avoid eating them, the Institute of Medicine panel said.
The problem is, they are everywhere.
"Having a little bit is probably OK," Eric Rimm, a nutritional epidemiologist at the Harvard School of Public Health who worked on the report, said in a telephone interview. "But avoiding it if at all possible is ideal."
Trans-fatty acids are a component of fat and found in all animal fats, from meat to butter. They are also made synthetically when food processors harden fat in a process called hydrogenization.
The U.S. Food and Drug Administration has been considering requiring food labels known as "nutrition fact boxes" to list trans-fat content, and asked the Institute to study the issue.
The report, issued last Wednesday, is part of a larger report that will be issued later in the year on macronutrients -- carbohydrates, fat and protein -- and how much people should aim to get in the diet.
It will join other reports that advise the government and public on what levels of vitamins people should eat. These advisories are used to set policy and guide, for instance, school lunch programs.
The report reviews scientific findings on trans-fats and finds that eating any at all raises levels of low-density lipoprotein -- the so-called bad cholesterol. Therefore, if a limit were to be set, it should be zero.
Rimm said the panel, made up of nutritionists, biochemists, pediatricians and others, decided not to do that.
"We can't tell people to stop eating all meat and all dairy products," he said.
"Well, we could tell people to become vegetarians," he added. "If we were truly basing this only on science, we would, but it is a bit extreme."
Alice Lichtenstein, a nutritional biochemist at Tufts University in Boston, said meat and dairy products are also high in saturated fat and therefore should be limited.
She said it would likewise be difficult to cut out all baked goods that are sources of trans-fatty acids.
"The major sources of trans-fatty acids in the diet are from partly hydrogenated vegetable fat, which is used for commercial frying," she said.
Fast food, frozen foods, cookies, crackers and pastries are all often loaded with them.
So is most stick margarine, but Lichtenstein, who served on the committee, said that does not mean people should return to using butter.
"Certainly butter is higher in saturated fat than margarine is in trans-fat," she said. "The scientific evidence shows that butter is worse than traditional stick margarine."
What people should do, Lichtenstein, is use softer margarines and oils that contain less hardened fat. For frying, liquid oils should always be used.
Margarines are also available that contain little or no hydrogenated fat.
The panel recommends that consumers look for the term "hydrogenated fat" in the ingredient lists of food they buy.
"The message, especially to food producers, is why don't you try to decrease levels?" Lichtenstein said.
"We hope this report will encourage new labeling laws so that trans-fat has to be on the label," Rimm added.