High-fructose corn syrup is the most heavily-used sweetener in the United States. It is extensively used in processed foods, including some that don't seem particularly sweet, because it is easier to ship than table sugar and significantly cheaper. Most of the HFCS produced in the U.S. is made by four large agribusiness corporations, Archer Daniels Midland, Cargill, Staley Manufacturing, and CPC International. Americans consume more HFCS than sucrose, driving concerns that perhaps it poses a danger to health.
From corn to syrup
The endosperm is the nutritive part of a seed, the food produced by the parent plant to feed its offspring during the first few days of growth before leaves break the surface of the earth, allowing the young plant to begin photosynthesis on its own. To produce cornstarch (cornflour to you Brits), the outer covering of the corn kernel and the embryo are removed, leaving the endosperm. The endosperm is soaked, then dried, and then pulverized, leaving the white starch behind. A series of enzymatic reactions convert the starch to sugar, largely glucose, yielding corn syrup. Another process, discovered in Japan in the 1970s, converts some of the glucose into fructose, which is sweeter than glucose or sucrose.
Starches are polymers made from long strings of glucose molecules. The first step in making corn syrup from cornstarch is using alpha amylase to break down the long starch chains into shorter units. Amylase is naturally present in saliva as well; this first step in corn syrup manufacturing mimics the first stage in digestion. The next step in the process uses glucoamylase to further break down these chains into glucose. The third enzyme, gluco-isomerase is used to partially convert the glucose slurry produced by the last step into a mixture of around 42% fructose and 50% glucose, with smaller amounts of some other sugars. The fructose is further purified to 90% concentration, which is then mixed with previous stage to yield a final product with about 55% fructose, although versions with greater concentrations of fructose exist. The high-fructose corn syrup is approximately as sweet as table sugar, but considerably cheaper to produce and use.
Health concerns
Sucrose is a disaccharide — a compound of two simple sugars, fructose and glucose. When the body metabolizes sucrose, then, it breaks down into equal portions of fructose and glucose. HFCS was originally formulated to replace the taste of sugar exactly, and indeed it has very similar proportions of fructose and glucose as does sucrose. Presumably it should be approximately as safe as sucrose, but concerns have arisen nevertheless. Since its introduction to the market, consumption of HFCS has increased steadily; at the same time, obesity has become dramatically more common in the United States. But caloric consumption has increased steadily during that time period as well, suggesting that the American public's general eating patterns are probably the cause for the rise in obesity.
What's undeniable is that there has been a major increase in obesity and in obesity-related illnesses. Insulin resistance syndrome and its big brother type 2 diabetes have become vastly more common in the industrialized world. Some evidence suggests that increases in fructose consumption may be linked to increased calorie consumption: studies in animals indicate that it may not stimulate the release of hormones that create a sense of fullness after eating; similar logic suggests a potential connection to metabolic disorders. But the evidence is weaker in humans, and blaming one particular food additive for Americans' overall tendency to eat too damn much is probably over-simplistic.
Many experts see the danger of HFCS as minor at worst. "It wouldn't make much difference if soft drinks were sweetened with sucrose or high-fructose corn syrup," said Michael Jacobson, director of the Center for Science in the Public Interest. The CSPI in particular has pushed for mandatory labeling in the United States of foods with added sugars; along with the World Health Organization they see the problem as primarily one of increased sugar consumption, mostly the result of too many processed foods. The WHO has released a report recommending that sugar consumption be limited to less than 10% of daily caloric intake. Since HCFS is so chemically similar to sucrose, the problem is probably one related to overconsumption of sugar, not to any particular kind of sugar.
References
Cornstarch at Encyclopedia.com. (http://www.encyclopedia.com/html/c1/cornstar.asp)
allrecipes.com Cook's Encyclopedia (http://allrecipes.com/advice/ref/ency/terms/6037.asp)
Forristal, Linda Joyce. "The Murky World of High-Fructose Corn Syrup". (http://www.westonaprice.org/motherlinda/cornsyrup.html)
"Is the increased use of high-fructose corn syrup responsible for the rise in obesity?" The Straight Dope. (http://www.straightdope.com/columns/040910.html)
Elliott, Sharon S. et alia, 2002. "Fructose, weight gain, and the insulin resistance syndrome". American Journal of Clinical Nutrition.
Squires, Sally, 2003. "Sweet but Not So Innocent?" The Washington Post. (http://www.washingtonpost.com/ac2/wp-dyn/A8003-2003Mar10?language=printer)
World Health Organization report on died and chronic disease (http://www.who.int/mediacentre/news/releases/2003/pr20/en/)
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