Findings gathered from a University of Barcelona study suggest calories contained in sweeteners may not be the only influence.
As well as the type of sugar consumed, there is the notable difference arising from consuming simple sugars dissolved in liquid compared to solid form.
These factors add to the ongoing debate as to whether the cardiovascular and metabolic effects of sugar-sweetened beverages (SSB) can be attributed to the simple sugars or are simply the consequence of an increase in caloric intake and weight gain.
SSBs are perhaps the prime example of simple sugars contained in liquid form.
These include sodas, colas, fruit punches, lemonade, and other fruit drinks with added sugars.
Compounds of choice used by the food industry to sweeten these beverages include sucrose (in Europe) and high fructose corn syrup (in USA).
Both contain roughly equal amounts of fructose and glucose.
In the study, female rats were given a liquid solution of either glucose or fructose (20% weight per volume (w/v)) in addition to their normal diet of solid food for a period of two months.
According to the research team, this period of ingestion in rats was roughly equivalent to 6 years of consumption in humans.
A control group, in which more rats received plain drinking water along with their food supply, was also set up.
After euthanizing the rats, glucose, triglycerides (fat) and cholesterol levels were recorded and compared to the control group.
Results indicated that total caloric intake in glucose-supplemented rats was higher than that of fructose-supplemented rats (1.15-fold).
Despite this, only the fructose group showed a significant increase in final body weight (by 1.1-fold).
Liver weight was increased only by fructose supplementation (by 1.4-fold vs control, and 1.3-fold vs glucose-fed rats), whereas adipose tissue weight was significantly increased in both sugar-supplemented groups (by 5.6-fold in the glucose group and 5.2-fold in the fructose group).
Blood lipid analysis also revealed levels of triglycerides were significantly increased in blood taken from fructose-supplemented rats (by 1.2-fold).
Additional results from the fructose group indicated more markers of vascular disease and liver damage than the glucose group.
These included decreased fat burning in the liver (a factor that can contribute to fatty liver) and impaired relaxation of the aorta, which can affect blood pressure.
High-calorie not guilty?
“Rats supplemented with a glucose solution, resulted in a compensatory response that is even worse compared with fructose supplementation, as liquid intake is higher and comparatively solid food consumption is reduced to a lesser extent,” commented the study’s authors.
“As a result, the total caloric intake is higher in rats receiving glucose than in rats with fructose supplementation.”
Previous suggestions have targeted the high calorie intake that simple sugars provide as the cause of adverse health effects.
However, results here showed that compared with the fructose (lower calorie) group, rats supplemented with liquid glucose (high calorie) exhibited less adverse metabolic and vascular effects.
The researchers thought the elevated adiponectin level and the subsequent enhancement of PPARα and eNOS phosphorylation in glucose-supplemented rats might exert some sort of protective mechanism that was not present in the the fructose group.
Source: American Journal of Physiology -- Heart and Circulatory Physiology.
Published online ahead of print: DOI: 10.1152/ajpheart.00339.2016
“Type of supplemented simple sugar, not merely calorie intake, determines adverse effects on metabolism and aortic function in female rats.”
Authors: Gemma Sangüesa, Sonali Shaligram, Farjana Akther, Núria Roglans, Juan C Laguna, Roshanak Rahimian, Marta Alegret