High-fructose Corn Syrup's Effect On The Brain

High-fructose corn syrup, or HFCS, is at the center of research and political controversy. Numerous studies have linked the sweetener to the obesity epidemic --- and related medical problems --- in the United States. For example, HFCS may fail to signal to your brain that you've had enough to eat, whereas other sugars do this. Other studies have examined HFCS's interaction with enzymes in the brain and its possible mercury contamination. On the other hand, public health authorities say there are too many unknowns about HFCS, and it's not time to call for a wholesale condemnation of it.

Leptin and Satiety

Prolonged consumption of food and beverages containing fructose-based sweeteners can lead to both overeating and reduce calorie-burning by your body. As a result, you can gain weight, says research published in the December 2008 issue of the "American Journal of Clinical Nutrition." This is because, unlike other sugars, your body's energy-balancing mechanisms don't get triggered by high-fructose corn syrup. One of these mechanisms is the leptin receptors in your brain. Leptin is called the "satisfaction" hormone because it tells your brain that you've had enough to eat. It can also tell the body to burn more calories based on how much you eat. Leptin works in the hypothalamus region of the brain, and research has demonstrated that your body's metabolism of high-fructose corn syrup may skip all of the processes that would trigger the work of leptin.

Brain Coenzyme for Fatty Acid Synthesis

Like leptin, your brain has numerous features that try to keep your body in a state of energy balance. An enzyme called malonyl-CoA has a role in brain signaling that determines your feeding behavior and appetite. Malonyl-CoA is a coenzyme in the brain that is involved in the formation of fatty acid chains. Research in the October 2008 issue of the "Proceedings of the National Academy of Sciences" demonstrates that when mice were fed a substance that blocked the synthesis of fatty acids, doing so blocked the molecules in their brain responsible for increasing appetite and those that depress their appetite. As a result, they ate less and lost weight.

Mercury-Contaminated HFCS

The process by which food manufacturers make HFCS involves the use of some materials suspected to contain mercury, a highly toxic substance in people. In a pair of studies reported on by "The Washington Post," nearly half the sample of commercially available, HFCS-containing food and beverages contained mercury. Mercury kills neurons in the central nervous system, which affect their signaling to the brain. The most affected neurons include the visual cortex, cerebellum and dorsal root ganglia. The symptoms of problems with these areas are confusion, depression, vision problems and disruption of sleep cycles.

To the Contrary

Some findings about HFCS conflict. For example, two small studies published in the February 2007 issue of the journal "Nutrition" and the December 2007 issue of the "American Journal of Clinical Nutrition" say that HFCS did not increase food intake, and leptin levels did not differ among participants after taking HFCS or beverages sweetened with other kinds of sugar. The studies were conducted on normal-weight individuals, and one of the studies found changes in the level of ghrelin, the hormone that signals your brain to eat more. Other research has demonstrated that leptin acts differently in overweight people. In addition, the Corn Refiners Association says that the sweetener industry uses mercury-free ingredients to produce HFCS and disputes the studies that said mercury was in many products containing HFCS. Other criticisms center on the use of animals vs. people in research and in studies that examine fructose exclusively. HFCS is about 55 percent fructose and contains other sugars.