By Ruth Kava, Ph.D., R.D.
Posted: Tuesday, May 16, 2006

ARTICLES
Publication Date: May 16, 2006

This article appeared May 16, 2006 on TCSDaily.com:

While love of money may be the root of most evil, when it comes to obesity, food ingredients -- especially those made in laboratories -- come in at a close second. (Just read the headlines). Witness the media hype around high-fructose corn syrup (HFCS), a sweetener that has come to replace regular table sugar (sucrose) in a wide variety of foods and beverages. HFCS is now firmly established as a member of the "bad foods" category -- but it shouldn't be.

The observation that increased consumption of HFCS by Americans has paralleled the increased prevalence of obesity, stimulated the hypothesis that HFCS is a major cause of obesity. Between 1970 and 1990, by some accounts, HFCS consumption increased by over 1000 percent, and now constitutes over 40 percent of caloric sweeteners added to foods and beverages in the United States.[i] And of course, over the same time period the prevalence of obesity in America has skyrocketed. This correlation is not the only basis for the hypothesis; to understand it, we have to consider the makeup of HFCS.

HFCS is made from cornstarch by the action of acid and then specific enzymes that break down some of the starch into a syrupy mixture of sugars -- fructose and glucose. HFCS contains either 42 or 55 percent fructose -- depending on exactly how the conversion is accomplished. In either case, the fructose content isn't much different from that of sucrose, which is composed of 50 percent fructose and 50 percent glucose.

When consumed by humans, sucrose passes through the stomach to the small intestine, where an enzyme breaks it down into those constituents -- again, glucose and fructose. These sugars are then absorbed into the body. The glucose and fructose of HFCS also pass into the small intestine where they are absorbed in the same manner, without the necessity of enzyme action.

Once they're absorbed into the bloodstream, whatever the source, the body handles fructose and glucose somewhat differently. Glucose in the blood causes the pancreas to secrete the hormone insulin, for example, while fructose does not. Further, these sugars are metabolized somewhat differently by the liver -- fructose by a biochemical pathway that more easily leads to production of fat. Such metabolic and hormonal differences have suggested to some that fructose is more likely to lead to an accumulation of body fat than is glucose, and that therefore, HFCS is more prone to lead to obesity than would be an equal amount of sucrose. But no one has demonstrated that this indeed occurs in humans; that is, without consumption of excess calories. Typically, studies that purport to show that HFCS is more "obesifying" than sugar have compared sugar to fructose, not to HFCS, which is not the appropriate comparison.

Epidemiological studies that have shown correlations between increased availability of HFCS and increased rates of obesity are useful for generating hypotheses -- but not for proving causation. Although such correlations have been found in analyses of American food and beverage consumption, they have not been apparent in data from other countries. For example, in Egypt, the prevalence of obesity in children has increased almost 4-fold in 18 years, and in England it's more than doubled in 10 years -- but in neither of these countries is HFCS commonly used in either food or beverages.[ii]

What about health effects other than obesity? Type 2 diabetes has also been linked to consumption of sugars. It is, however widely recognized by experts that diabetics must control their consumption of all metabolizable carbohydrates -- starches as well as sugars -- and that HFCS metabolism is essentially the same as that of sucrose.[iii]

Another possible negative effect of consumption of large amounts of sugars is an increase in levels of lipids in the blood -- this has been shown in rodents fed very high levels of fructose, and in humans, it is known that a high-carbohydrate, low-fat diet can increase blood levels of triglyceride -- but this is not specific to HFCS or to fructose.[iv]

HFCS has been singled out as a unique contributor to the obesity epidemic without sound scientific justification. But HFCS is an ingredient that has useful properties for food and beverage formulations. It helps foods retain moisture and helps control crystallization and microbiological growth; it is economical in comparison to sucrose; and blends well with other sweeteners and flavorings. It may well be the case that overconsumption of HFCS has played a role in the upsurge in obesity in America over the last few decades, but it's hard to see that it is any more culpable than any other good-tasting ingredient.

The author is Director of Nutrition, American Council on Science and Health.

[i] Bray GA, Nielsen SJ, Popkin BM. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. Am J Clin Nutr 2004;79:537-43.

[ii] Ebbeling CB, Pawlak DB, Ludwig DS. Childhood obesity: public-health crisis, common sense cure. Lancet 2002;360:473-482.

[iii] Franz MJ Bantle JP Beebe JP et al. Evidence-based nutrition principles and recommendations for the treatment and prevention of diabetes and related complications. Diabetes Care 2002;25:148-198.

[iv] Schorin MD. High Fructose Corn Syrups, Part 2 Health effects. Nutrition Today 2006;41:70-77.

See also: ACSH's full report on Sugar Substitutes and Your Health.