The study, published in the May 21 issue of the Journal of the American College of Cardiology, focused on three dozen volunteers, each of whom ate a 900-calorie McDonald's meal containing 50 grams of fat: an Egg McMuffin, a Sausage McMuffin, two hash browns and a non-caffeinated drink.
"I think it sort of confirms what people have known for a while -- that is, eating fruits and vegetables long-term is beneficial in decreasing the risk of cardiovascular disease," says study co-author Dr. Gary D. Plotnick, a professor of medicine at the University of Maryland School of Medicine.
Plotnick cautions, however, that the study results are preliminary and need to be confirmed by a much larger study. And he warns against assuming you can take a capsule concentrate containing fruit and vegetables, then eat high-fat meals without worry.
"What I don't want to get across is you can take pills and eat anything you want because there are detrimental effects of high-fat meals independent of what we looked at," he says. For example, Plotnick says, the study did not examine the high-fat meal's effect on cholesterol.
Before the meal, researchers divided the volunteers into three groups. For four weeks, one group received the capsule concentrate; one group, the capsule concentrate and an herbal supplement; the third group, a placebo.
The fruit-and-vegetable supplements appeared to help arteries retain much of their ability to expand in response to a sudden increase in blood flow, the study found.
Among those who took only placebos, however, the high-fat meal significantly reduced the blood vessels' ability to expand with an increase in blood flow. (Addition of the herbal supplement had no significant effect on the vessels.)
The researchers measured blood vessel response three hours after the meal by using a blood-pressure cuff to stop blood flow in the arm for five minutes, then releasing the cuff, causing a sudden surge in blood flow. After a high-fat meal, the inner lining of blood vessels -- called the endothelium -- does not expand as well in response to an increase in blood flow because the endothelium doesn't release as much nitric oxide, Plotnick says.
The researchers received support for the study from Natural Alternatives International, the manufacturer of the fruit-and-vegetable capsules used in the research.
The researchers suggest the antioxidants in fruits and vegetables may have helped endothelium function among those who took the concentrate. Diminished function of the endothelium can be an early sign of atherosclerosis, the gradual blocking of arteries that can lead to heart attack and stroke, the study says.
Researchers not involved in the study say they wouldn't read too much into its results.
In an editorial in the journal accompanying the study, Dr. Jane E. Freedman, associate professor of medicine at Boston University School of Medicine, says the study presents a possible reason for protective benefits of compounds in fruits and vegetables. But, she writes, further research is needed to determine the possible benefits of the fruit-and-vegetable concentrate.
"This is a very limited study that should not be over-interpreted," Freedman says.
She also says the study results can't be extended to other fatty foods, and adds that endothelium function has not been proved to correlate with cardiovascular disease.
Alice H. Lichtenstein, a professor of nutrition, science and policy at Tufts University School of Medicine, points out that ingredients in the concentrate -- but not found in fruits and vegetables -- could have affected the study's outcome.
Lichtenstein, vice chairwoman of the American Heart Association's Nutrition Committee, says the study focused on a "very narrow question asked under very controlled and extreme experimental conditions."
"It would be premature to make a recommendation based on this study," she says.