Not all saturated fats are created equal. A University of Nebraska nutritional scientist's research shows that some saturated fats promote heart disease, while others actually may reduce cholesterol absorption.

Tim Carr studies fats' role in heart disease. Studies elsewhere have examined fats' effects on cholesterol levels and established high cholesterol levels as a major heart attack risk. Carr studies how fats affect the liver.

Recent research shows chemical changes in the liver can lead to heart disease, opening a new frontier for heart disease research.

"We've only begun to understand the liver," Carr said.

Because studying liver function in humans is impractical, Carr works with hamsters fed a mix of fats that mimics the average American's fare. His research revealed some fats alter liver function and cause atherosclerosis, or hardening of the arteries.

Carr's research shows saturated fats found in tropical oils, such as palm oil and coconut oil, promote heart disease because they contain cholesterol-raising palmitic acid.

He found that saturated fats in beef and cocoa butter don't promote heart disease.

They contain stearic acid, a saturated fatty acid that Carr found significantly inhibits cholesterol absorption. Normally, hamsters absorb about 50 percent of the cholesterol they consume. When stearic acid was added to their diet, cholesterol absorption dropped to 20 percent.

"That's a whopping number in any scientific study," Carr said.

Carr also found monounsaturated fats, such as those in olive oil, can cause heart disease. This confirms his previous research at North Carolina's Bowman Gray School of Medicine showing these fats caused as much heart disease as certain saturated fats.

Cholesterol moves into the liver, where it either secretes into the bloodstream or is excreted from the body. Carr found monounsaturated fats cause cholesterol to move from the liver into the bloodstream faster, increasing cholesterol levels and heart disease risk.

"The general belief is that olive oil is healthy," Carr said. "But it's still a fat."

Fats are calorie-dense and Americans should eat fewer calories to avoid obesity, the NU College of Human Resources and Family Sciences researcher noted.

Carr also found that trans-fatty acids in foods with hardened vegetable fat such as margarine, shortening and some crackers and cookies don't promote heart disease, as some health groups have suggested. Some studies claim trans-fatty acids create more cholesterol in the blood than saturated fats, but Carr found they create less.

"Trans-fatty acids are just another fat, certainly no worse than saturated fats," he said.

Because it's unlikely any single food prevents heart disease, Carr recommends eating a balanced diet rather than fretting over individual fats.

Choosing among fats "is analogous to rearranging the deck chairs on the Titanic," he said. "We are studying the deck chairs - whether these fats influence body chemistry. The answer is they do, but what we don't know is whether selecting a specific type of fat will prevent heart disease."

Meanwhile, "the best we can do is to decrease the number of calories we consume and try to reduce obesity," he said.

Carr's research eventually could help explain how heart disease progresses in humans.

That's significant since people often don't know they have the disease until they have a heart attack.

He plans further studies of the liver's role in heart disease and possibly the health benefits of eating beef, he said.

Heart disease is Nebraska's and the nation's leading cause of death, yet scientists know little about biochemical changes linked to heart disease.

"We are simply finding one more piece of the puzzle," Carr said.

This Institute of Agriculture and Natural Resources research is funded by a USDA competitive grant.

- Molly Klocksin

Nutritional Scientist Tim Carr studies fats' role in heart disease. Above,He examines a hamster artery through a digital imaging microscope. The blotchy areas indicate heart disease developing in the animal.Below,He uses a gas chromatograph to measure the types of fats in a hamster's diet.