Diligent readers of food and beverage labels may have noticed an increasingly common ingredient in some health and energy drinks: crystalline fructose.
To some, the ingredient is a reassuring sign that the product hasn't been sweetened with high fructose corn syrup, a sweetener that's been falling out of consumer favor over concerns of a disputed link to obesity and diabetes. Others, however, may have found themselves wondering what, exactly, is crystalline fructose? And is it really any different from high fructose corn syrup?
"Technically, yes, but physiologically, no," says Roger Clemens, a professor at the USC School of Pharmacy whose research has focused on functional foods, food processing and nutrition. The two ingredients are chemically distinct, Clemens says, but their nutritional ramifications vary only slightly.
High fructose corn syrup and crystalline fructose are made from the same starting material: corn. In the U.S., this is an abundant and cheap source of fructose, the plant-sugar responsible for making many fruits so naturally sweet.
But though high fructose corn syrup often contains about 55% fructose (the rest is glucose), crystalline fructose is the result of several extra processing steps which yield a product that is close to 100% fructose. (According to federal standards, crystalline fructose is, by definition, at least 98% fructose; the remaining fraction is water and minerals.)
From a food-manufacturing perspective, a nearly pure-fructose sweetener is advantageous because it's up to 20% sweeter than sucrose, or table sugar, says Craig Ruffolo, vice president of McKeany-Flavell Co., a sweetener industry analysis firm in Emeryville, Calif. That means manufacturers can achieve a high level of sweetness without adding as much volume to a product.
That extra sweetness also means crystalline fructose adds fewer calories to a sweetened food or drink compared with table sugar or high fructose corn syrup (it's 5% sweeter than the syrup). This is why it's often included in drinks marketed to more health-conscious consumers.
The difference in calories is typically small -- a drink sweetened with crystalline fructose in place of high fructose corn syrup, for instance, would have about 5% fewer calories, says Ihab Bishay, a Chicago-based independent food science consultant to the sweetener industry. "But if you're concentrating on your calories, it's a help," he says.
Crystalline fructose may also have an added benefit for a specific subset of the population: those with diabetes and pre-diabetes. A review of several dozen studies on fructose, published in the American Journal of Clinical Nutrition in November, found that people who consumed more fructose relative to other sugars tended to have lower blood glucose concentrations than people on normal diets.
The report was funded by the sugar industry, but its findings correlate with what is known about how the body responds to different sugars.
In the body, the amount of glucose in the blood is controlled by insulin, the hormone that helps move the sugar out of the bloodstream and into cells, where it's used as an energy source. Thus, glucose-containing sweeteners, such as high fructose corn syrup and sucrose, can cause dangerously elevated blood sugar levels in people whose bodies don't produce enough insulin or respond sluggishly to the hormone.
Fructose, on the other hand, isn't controlled by insulin, which is why it's sometimes called a "diabetic-friendly carbohydrate," Clemens says.
Paradoxically, however, some researchers speculate that fructose itself may be responsible for the current high rates of diabetes and obesity. The theory: Because fructose doesn't trigger insulin secretion, the body doesn't register that its energy needs have been met, leading the body to crave more and more food.
A handful of animal and short-term human studies have supported the possibility that fructose could be responsible for obesity, diabetes, and other conditions, says Mary Ellen Camire, professor of food science and nutrition at the University of Maine in Orono, but the theory is still being debated among nutritional scientists. "We need more and better studies," she says.
Consuming pure fructose may have other strikes against it. A 2005 study by researchers at the University of Kansas Medical Center in Kansas City showed that consuming more than 25 grams of fructose a day often causes gastrointestinal distress, including stomach pain and diarrhea. The majority of American adults consumes more than 50 grams daily, mostly through corn syrup added to processed foods and drinks.
For the average consumer, Camire says, the nutritional differences between high fructose corn syrup and crystalline fructose are perhaps beside the point.
"It doesn't matter if it's fructose, glucose or sucrose," she said. "Do you really want to be consuming all that extra sugar?"