March 30 (UPI) -- Milkshakes have long been popular treats for children and adults alike, but a recent study shows that, despite being delicious, they could have a dangerous effect on heart health.
Researchers at Medical College of Georgia report in a study published this week in the journal Laboratory Investigation that milkshakes can start the body on the road to heart disease.
In the study, researchers saw the fat content of the milkshake quickly transform healthy red blood cells into small, spiky cells that disrupt the blood vessels.
"The impact of a single high-fat meal on endothelial function has been observed before," Dr. Ryan A. Harris, clinical exercise and vascular physiologist at the Georgia Prevention Institute at the Medical College of Georgia, told UPI. "However, the impact that the high-fat meal has on the red blood cell and mechanistic pathway of myeloperoxidase production is the new and novel aspect."
Four hours after five healthy and active young men consumed a milkshake containing about 80 grams of fat and 1,000 calories, the participants' blood vessels were less able to relax and their immune systems responded as though they had been provoked by an infection. They also had significant increases in cholesterol, triglycerides and free fatty acids, according to blood tests.
Red blood cells, which are the most abundant in the body, carry oxygen and are extremely flexible so they can flow through blood vessels essentially unnoticed.
Foods like milkshakes take a cumulative toll on the body, researchers say, noting that people have had heart attacks after consuming high fat meals.
"We see this hopefully as a public service to get people to think twice about eating this way," Dr. Neal L. Weintraub, a cardiologist and associate director of Medical College of Georgia Vascular Biology Center in Augusta, said in a press release.
The study was the first to look specifically at red blood cells, the most abundant cell in blood. With a single high-fat meal, the red blood cells changed and spewed poison.
"They changed size, they changed shape, they got smaller," Harris said. "You are looking at what one, high-fat meal does to blood-vessel health."
Healthy males in the study who instead consumed a meal of three big bowls of sugar-coated flakes with non-fat milk, but the same number of calories and no fat, did not experience the same harmful changes to their blood, red blood cells and blood vessels.
The cells and blood of participants who were given a milkshake contained myeloperoxidase, or MPO, which is an enzyme with a type of white blood cell that has been linked to stiff blood vessels, oxidative stress and heart attack when in high levels.
MPO impairs the ability of blood vessels to dilate, even leading to oxidation of HDL cholesterol, which converts this usually cardioprotective cholesterol into a cause of cardiovascular disease. When acquired by a diseased artery, MPO can destabilize plaque buildup and result in a stroke or heart attack.
Additionally, MPO impacts the cytoskeleton of red blood cells, which are usually plump and smooth.
"Your red blood cells are normally nice and smooth and beautiful and the cells, after consumption of a high-fat meal, get these spikes on them," said study author Dr. Julia E. Brittain, a vascular biologist at the center, comparing the effect to what large ice chunks do to a river.
The researchers found that in mice, and in some of Brittain's other human studies, the unhealthy changes also resolve at about eight hours unless the high-fat meals continue.
The new study focused only the effects of a high-fat meal four hours after consumption.
"All of the negative physiological responses that we observed occurred four hours following consumption of the high-fat meal," Harris said. "Accordingly, the response is likely after digestion when the macro nutrients have been digested and [are] already causing havoc in the circulation."
The researchers noted that longer-term impact on humans would be difficult to explore because they wouldn't want to expose study participants to such an unhealthy risk. But when mice were fed a high-fat diet, the changes to their red blood cells and blood were permanent, the researchers said.
Harris said that other foods with similar levels of fat can have the same result.
"There is some literature demonstrating that it is the saturated fat that is the culprit," he said. "Accordingly, I suspect that all foods high in saturated fat will have a similar effect."
While Harris said sugar "is bad" and similar dysfunction following high sugar loads has been seen in patients with diabetes, it's not the same.
"The present study gave an iso-caloric meal of frosted flakes that was comprised of carbohydrates, which did not have any impact on endothelial function and red cell morphology in the healthy participants we studied," Harris said.
Weintraub said the effects can be countered by eating healthy, exercising regularly and monitoring cholesterol and blood pressure levels. Past studies at the school indicate a single aerobic exercise session by young healthy individuals can counteract the unhealthy milkshake.
While the body can recover from ingesting unhealthy levels of fat, researchers say they are unsure if the body adapts over time to higher levels of fat.
"Although we don't have any data in humans to support this answer, epidemiological data would suggest that there is no adaptation," Harris said. "For example, those who routinely eat high fat meals are typically obese and obesity is linked with vascular dysfunction."
A fat intake of 20 percent to 35 percent of a healthy adult's daily calories is recommended by the American Heart Association.
"The take-home message is that your body can usually handle this if you don't do it again at the next meal and the next and the next," Brittain said.