Jury out on high fructose corn syrup and obesity

High fructose corn syrup (HFCS) has been singled out as having special properties that make Americans fatter than sugar and other energy sources with identical calorie contents.

But an analysis by the University of Maryland Center for Food, Nutrition, and Agriculture Policy (CFNAP), now appearing online in Critical Reviews in Food Science and Nutrition, says there isn't enough research to conclude that high fructose corn syrup contributes to weight gain any more than any other energy source, such as sucrose (sugar.)

The CFNAP study team, led by Richard Forshee, Ph.D., recommends that more research be conducted on HFCS, including whether HFCS is metabolized differently than sucrose. They also recommend updating the USDA food composition and nutrient databases to reflect recent research.

For their study, the team used a literature search and developed argument diagrams to visualize the hypotheses being proposed for the role of HFCS (not fructose) in contributing uniquely to weight gain. They also conducted original research to assess the potential impact of regular carbonated soft drinks on body mass index, using data from the longitudinal studies and the food availability reports available in the peer-reviewed literature.

HFCS Targeted
High fructose corn syrup has been targeted as a special suspect in causing obesity, in part because of timing. “All of us are very concerned about the pronounced increase in the obesity rate in the United States over the past few decades, and researchers are searching for ways to explain it,” said Forshee. “Some have suggested that high-fructose corn syrup may be the culprit because its use in food and beverages has expanded during roughly the same time period as the increase in obesity rates. This kind of analysis—comparing two trends over time—is called an ecological analysis, and it is widely recognized that an ecological analysis is weak and can be very misleading.

“Many other trends, from smoking rates to two-income households to computer use, have also been roughly coincident with the rise in obesity, and ecological analysis cannot determine which of the trends are truly associated with the obesity rate,” said Forshee. “We dug deeper to examine more robust forms of analysis.”

What is HFCS?
In sorting out the impact of high fructose corn syrup on obesity, the study says, it's important to understand the differences in sweeteners – what is actually HFCS and what is not?

According to Maureen Storey, Ph.D., CFNAP director and a member of the study team, there are three types of HFCS products (HFCS-55, HFCS-42, and HFCS-90), but only HFCS-55 and HFCS-42 are commonly used as sweeteners. HFCS-90 is mainly used in the production of HFCS-55, but is seldom directly added to foods and beverages. The composition of HFCS-55 (55% fructose and 42% glucose) is very similar to that of sucrose (50% fructose and 50% glucose). HFCS-42 (42% fructose and 53% glucose) actually contains less fructose than sucrose does.

HFCS-55 is used mainly in beverages, such as carbonated and non-carbonated soft drinks; HFCS-42 is used to sweeten a wide variety of foods.

Recommendations
The team makes these recommendations:

• Fill gaps in the research, including gathering data on special vulnerabilities of sub-populations that may be predisposed to obesity and better measures of energy expenditure and its importance to weight control.
• Update the USDA food composition and nutrient databases. Says Storey, “Without this critical information, nutrition and toxicological research will be flawed by out-of-date data. Fructose levels in food products and actual fructose consumption is unknown. In addition, there are no chemical methods that can distinguish naturally-occurring dietary fructose from fructose added by manufacturers either as sucrose or HFCS.”
• Increase access to federally funded longitudinal datasets so researchers can replicate each other's findings.

Funding
The study was funded by Tate and Lyle, with an unrestricted grant to hold the workshop, which was the only obligation. Tate and Lyle did not participate in the workshop, nor did the corporation have any input into the literature search, development of the argument diagrams, design of the original research conducted by CFNAP, or the decision to publish.