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Tuesday, 12 February, 2002, 15:17 GMT
Stress link to heart-danger fats
Stess has been linked to heart disease
Stess has been linked to heart disease
Stress causes the body to retain heart-damaging fats in the blood for longer, researchers have found.

The findings offer one explanation for why stress is linked to heart disease.

A team from Ohio State University compared how long it took people experiencing short periods of psychological stress to clear heart-damaging fats from the bloodstream, compared to people who had been resting.

They were looking at fats called triglycerides, a type of fatty acid found in the blood.

Cholesterol is the most important predictor of coronary heart disease risk, but recent studies have suggested a link between high triglyceride levels and increased risk of coronary heart disease and stroke.

The researchers found stress caused triglycerides to stay in the bloodstream for longer.

Hormone link

The study involved 70 healthy, non-smoking middle-aged volunteers, half were men and half women.

Half of the group were between the ages of 40 and 48 and the rest between 54 and 61.

If a person has a high-fat snack or meal during a time of stress, that fat is going to be circulating in the blood for a longer period of time

Catherine Stoney, Ohio State University
These age groups were chosen so researchers could compare pre and postmenopausal women to examine the theory that reproductive hormones might affect how triglycerides are cleared from the bloodstream.

Each of the 70 underwent two 40 minute tests within a three day period.

In both tests, a solution containing triglycerides - the equivalent of about 100 calories - was administered into the volunteers' veins to mimic what would happen in a person's bloodstream hours after they ate a meal containing fat.

In one session, the volunteers rested. In the other, the volunteers were administered the triglyceride solution and were then given stressful tests including having to prepare and give a videotaped speech, a difficult word problem, drawing mirror images, and quick-fire maths tests, while their triglyceride level was monitored.

Clearing fats

The researchers found triglyceride levels declined by an average of 2.8% a minute in the stress-inducing test session, compared to a 3.2% per minute in the resting session.

In some people there were significant differences in the way they metabolised fats in the two tests, while in others the differences were quite small.

But in all cases, stress meant a person processed the fats more slowly.

In the resting session, women were found to clear triglycerides out of their bloodstream more quickly than men.

There was also no difference in how pre and post-menopausal women reacted to the tests, even when those who had been through the menopause were taking HRT, suggesting reproductive hormones do not affect how triglycerides are processed.

There was no difference in how quickly men and women cleared triglycerides during stress.

Catherine Stoney, co-author of the study and professor of psychology at Ohio State University, said: "During stress, people are not metabolising fat as rapidly and efficiently.

"If a person has a high-fat snack or meal during a time of stress, that fat is going to be circulating in the blood for a longer period of time.

"That means it may be more likely to be deposited in the arteries where it can contribute to heart disease."

Belinda Linden, medical spokesperson for the British Heart Foundation, said: "This research indicates that triglycerides may stay in the blood for longer periods of time when people are stressed.

She added: "Although it does add to our understanding of stress and triglycerides, the research has only used a small sample of people in one geographical area.

"Further large-scale randomised research is needed."

The study appears in the journal Psychophysiology.

See also:

15 Mar 01 | Health
Obsessives risk heart attacks
20 Jan 00 | Health
Mondays 'bring heart attacks'
04 Mar 99 | Health
Caffeine drives up stress levels
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