Is this a mere coincidence? Or is there something more insidious about this liquid sweetener that is literally short-wiring our metabolism and making us fat? The debate is in full swing.
High fructose corn syrup is not the same as the corn syrup you use to make pecan pie or candy during the holidays. Made by treating cornstarch with enzymes, it's about half fructose and half glucose (regular corn syrup is all glucose).
You won't find bottles of this stuff on supermarket shelves. But you will see it listed as a primary ingredient in soft drinks and fruit beverages, which are the leading sources of high fructose corn syrup in the American diet.
It also pops up in some surprising places -- everything from applesauce to energy bars. Even ketchup, barbecue sauce and bottled marinades contain the sweetener.
Fructose: Treated differently than other sugars?
So what's the big deal? Some experts believe our bodies treat high fructose corn syrup more like a fat than a sugar. They think it may even trigger metabolic changes -- tricking us to eat more and store more fat.
Peter Havel, a nutrition researcher at the University of California, Davis, who has studied the metabolic effects of fructose, has found that several hormones involved in the regulation of body weight do not respond to fructose as they do to other types of sugars, such as glucose.
"Fructose doesn't appear to signal the hormonal systems involved in the long-term regulation of food intake and energy metabolism," he said.
Havel's research shows that fructose does not stimulate insulin and leptin -- two hormones that help turn down the appetite and control body weight. At the same time, fructose does not suppress our body's production of ghrelin, a hormone that increases hunger and appetite.
Other studies have shown that fructose kicks more fat into the bloodstream in the form of triglycerides, which may increase the risk of heart disease.
The debate picked up steam recently with the release of a new study in the July issue of Obesity Research that suggests fructose alters our metabolic rate in a way that favors fat storage.
Havel and researchers at the University of Cincinnati and the German Institute of Human Nutrition fed mice a fructose-sweetened drink, which caused them to store more fat than mice that drank water -- even though they did not consume more calories.
These findings suggest that calorie intake may not be the only explanation for weight gain when people include fructose in their diets, the authors concluded.
Only part of the blame
The fructose-sweetened drink given to the mice was chosen to imitate the high fructose corn syrup found in soft drinks, but some food-industry groups are crying foul.
Richard Adamson, vice president of scientific and technical affairs for the American Beverage Association, said the study was "seriously flawed" because "mice are not humans and fructose is not high fructose corn syrup."
The researchers used pure fructose rather than a high fructose corn syrup mixture (typically 42 or 55 percent fructose in combination with glucose). In fact, all of the studies to date have focused on a fabricated fructose fluid and not high fructose corn syrup.
The mice in the study also drank diet soda and a soft drink sweetened with sucrose or table sugar -- and neither increased body fat. Adamson said he predicts a soda sweetened with high fructose corn syrup would have similar results since this corn-derived sweetener has virtually the same composition as sucrose, which is 50 percent fructose and 50 percent glucose.
Because both sweeteners break down into glucose and fructose in about equal proportion, our bodies can't really tell the difference, Adamson said.
Though our intake of high fructose corn syrup appears to mirror the rise in obesity, there's no evidence linking the sweetener to the cause, according to Audrae Erickson, president of the Corn Refiners Association, a trade organization representing companies that make corn-based products and ingredients.