Susan M. Kleiner, PhD, RD, CNS, FACN

What food could possibly be so bad that it deserves such an ominous title? With almost 60 percent of American adults overweight, and half of those obese, research is beginning to identify one ingredient in the food supply that may be a primary cause of the epidemic. If true, wouldn't you call it "The Devil's Candy"?

My first semester in graduate school I took a course called Food Science, the study of ingredients in foods and how they work during cooking and processing. It was 1980. I'll never forget Professor Grace Petot's comments during a particularly interesting lecture on sweetening agents in food. "High-fructose corn syrup has recently been introduced into the food supply," she said. "Compared to sucrose, it is a very inexpensive sweetener, and will likely replace sugar in most processed foods. Our understanding of how fructose works in the body is very limited, and we have no idea how this will affect the population once it is found almost everywhere in the processed food supply," As I read the results of several new studies on fructose, weight control and health, her words rang in my ears.

HFCS: What is it?
Corn syrups are manufactured from cornstarch. They contain varying proportions of glucose and other simple sugars. High-fructose corn syrup (HFCS) is corn syrup containing a high proportion of glucose, which is then treated with an enzyme that converts part of the glucose to the much sweeter fructose. This process produces a very inexpensive replacement for cane sugar. HFCS can contain up to 90 percent fructose, but most of the HFCS found in beverages contains approximately 55 percent fructose.

The commercial use of high-fructose corn syrup began in the 1970's. By 1985, HFCS accounted for about 35 percent of the total amount of sweeteners by dry weight in the food supply. Since 1970 the per capita use of HFCS has increased from only a half pound to 62 ½ pounds in 1997, the last year that data indicating these trends were collected. Data from 1997 estimated the total average fructose consumption to be 97 grams per day, equivalent to 388 calories per day.

In all likelihood fructose consumption is significantly higher today than it was in 1997. The major sources of HFCS in the diet are soft drinks, and soft drink consumption continues to rise. A 1998 study on soft drink consumption titled "Liquid Candy" published by the nonprofit Center for Science in the Public Interest (CSPI) reported that Americans are drinking twice as much soda pop as they did 25 years ago. In 1998 the average male 12-19 years old consumed more than 2 cans of soda per day. That is 50 grams or 200 calories of fructose every day, or about 10% of your average energy need, without considering other dietary sources of fructose.

So fructose consumption takes up a significant amount of your calories every day, and the increase in fructose consumption has coincided with a remarkable increase in obesity during the same 2 decades. Is this just a coincidence, or is something else going on?

Fructose and Syndrome X
Researchers from the Department of Nutrition at the University of California, Davis, the US Department of Agriculture Western Human Nutrition Research Center at Davis, California, the Monell Chemical Sense Institute and the University of Pennsylvania, Philadelphia, have recently published a landmark review of the scientific literature on fructose, weight gain, and the insulin resistance syndrome, popularly called Syndrome X. They have proposed the theory that fructose in the form of the ingredient high-fructose corn syrup may be primarily responsible for the epidemic of obesity and abnormalities seen as part of Syndrome X, including insulin resistance, impaired glucose tolerance, hyperinsulinemia, hypertriacylglycerolemia, and hypertension.

HFCS makes you fat
It has been understood for several years that fructose is metabolized differently in the body than glucose. While the body prefers to metabolize glucose into energy or store it as glycogen to fuel muscle cells, fructose is metabolically processed in the liver and preferentially turned into fat rather than used as energy. Human studies have shown that fructose ingestion increases rates of fat production, but ingesting the same number of calories as glucose does not cause the same response.

Not only does the fructose that you eat turn into fat, but it shuts down the body's mechanisms that keep it from turning into a fat-making machine. According to numerous animal studies and several human studies, fructose does not stimulate the production of 2 key hormones, insulin and leptin, which are involved in the long-term regulation of energy balance. Unlike glucose, fructose does not stimulate the secretion of insulin from the pancreas. While at low levels of fructose intake this may be desirable for Type 2 diabetics and others, it is far from desirable for anyone trying to lose body fat. Insulin influences the regulation of body fat by inhibiting food intake and increasing energy expenditure. After a meal, insulin is secreted in response to the carbohydrate eaten. Along with its job of ushering glucose into cells, insulin acts as a signal for how much food has been eaten and when it is time to stop eating. If insulin is not secreted then there is no mechanism to turn off energy intake, and weight gain and obesity may develop.

Leptin is a protein manufactured in fat cells that functions as a circulating signal to limit fat stores and fat production by inhibiting food intake and increasing energy expenditure. Insulin stimulates leptin production, thus playing a key role in the regulation of body fat stores. When carbohydrate is consumed as part of a meal it is digested to glucose, insulin is secreted and stimulates leptin production, hunger is abated and energy expenditure is increased. Body weight stays in balance. When HFCS is consumed this cascade of events is by-passed, crippling the internal mechanisms for calorie control and energy balance.

In addition to its pivotal role in the development of obesity, the research group from California and Pennsylvania propose a chief role for fructose in the development of insulin resistance, impaired glucose tolerance, hyperinsulinemia, abnormal lipid profiles, and high blood pressure.

Liquid Candy
Animal studies have consistently shown that high-fructose diets lead to weight gain. A number of small studies have begun to investigate the impact of high-fructose diets on body weight in humans. The design for the human studies have followed subjects' calorie intake when approximately 300 calories of soft drink have been added to their intake every day. While in most cases energy intake will balance out over time allowing for maintenance of body weight, when the soft drinks with fructose were added energy intake was not balanced, resulting in an overabundance of calories and weight gain.

One study examined the effect of a sucrose beverage compared to an artificially-sweetened beverage on the food intake and body weight of overweight subjects. Sucrose, or table sugar, is a disaccharide made of about half glucose and half fructose. So the sucrose-sweetened beverages were 50 percent fructose. After 10 weeks, the sucrose group had increased energy intakes (28 percent), higher body weight and fat mass and higher blood pressure. The group using the artificially-sweetened beverages with aspartame (54%), acesulfame-K (22%), cyclamate (23%) and saccharin (1%), actually had lower calorie intakes and lost body weight and fat mass, and lowered blood pressure after 10 weeks.

Another study looked at liquid versus solid carbohydrate and the effects on food intake and body weight. During 2, 4-week periods, subjects either ate or drank solid jelly beans or liquid soda to add extra carbohydrate to their diets, and then ate on their own. Energy intake during the solid period maintained at balance levels, showing a compensation of calories for the added solid carbohydrate. However, during the liquid period, no compensation for the extra calories occurred and total daily calorie intake increased by 17 percent. Body weight and BMI increased significantly, indicating that liquid carbohydrate calories are not recognized by physiological systems that control energy balance.

Fructose by any other name...
There is mounting evidence that fructose, in the form of high-fructose corn syrup or sucrose, is an undesirable ingredient in the diet. While small amounts are probably not harmful and would not interfere with energy metabolism, the large amounts found in soft drinks and many processed foods may be at the root of the body's inability to maintain energy balance and control body weight.

In spite of the fact that fructose is commonly known as "fruit sugar", this recommendation should not be translated into the exclusion of the naturally occurring fructose found in fruits and vegetables. According to the authors of the Syndrome X review, "The consumption of fruit and vegetables should continue to be encouraged because of the resulting increased intake of fiber, micronutrients, and antioxidants. In addition, the intake of naturally occurring fructose is low, about 15g/d, and is unlikely to contribute significantly to the untoward metabolic consequences associated with the consumption of large amounts of fructose."

What's left to drink?
Well, my first recommendation is water, and then milk and 100 percent fruit juice. But if you can't imagine a day without a soda, try a diet soda instead. I never really thought I'd see myself recommending diet pop, but the fact is that we know that the amount of HFCS in soda is going to keep you from getting those six-pack abs you've been working toward, and the diet soda is turning out to be a decent alternative. At least for now.

And watch out for all the other foods laced with HFCS. All sweetened beverages, candy, ice cream, frozen yogurts, popsicles and fruit bars, ketchup, pasta sauce, even hamburger buns use HFCS in varying amounts. When you add these foods to a couple of cans of soda every day, you've got a heavy load of fructose. Read ingredient labels to educate yourself and make informed choices.

Much more research needs to be done, but the picture is beginning to look awfully clear. Professor Petot's intuition was right. When you mess with the food supply to the degree that has been done with high-fructose corn syrup, you're making a deal with the devil, and someone's going to pay. The food manufacturers have made the deal, and we've been paying with our health and our lives. It's time to close the HFCS account.

References

1. DiMeglio DP, Mattes RD. Liquid versus solid carbohydrate: effects on food intake and body weight. Int J Obes Relat Metab Disord 2000;24:794-800
2. Elliott SS, Keim NL, Stern JS, Teff K, Havel PJ. Fructose, Weight gain, and the insulin resistance syndrome. Am J Clin Nutr 2002;76:911-22
3. Harnack L, Stang J, Story M. Soft drink consumption among US children and adolescents: Nutritional consequences. J Am Diet Assoc 1999;99:436-441
4. Jacobson, M. "Liquid Candy. How soft drinks are harming Americans' health". Center for Science in the Public Interest, October 21, 1998
5. Ludwig DS, Peterson KE, Gortmaker, S. Relation between consumption of sugar-sweetened drinks and childhood obesity: a prospective, observational analysis. Lancet 2001;357:505-8
6. Raben A, Vasilaras TH, Moller AC, Astrup A. Sucrose compared with artificial sweeteners: different effects on ad libitum food intake and body weight after 10 wk of supplementation in overweight subjects. Am J Clin Nutr 2002;76:721-9

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