Fructose is more present in the American diet than ever, thanks to the increased use of high-fructose corn syrup, or HFCS, and sugar. Table sugar, or sucrose, is made of 50 percent glucose and 50 percent fructose, while HFCS contains between 55 and 90 percent fructose, according to the February 2005 issue of "Nutrition & Metabolism." Moreover, the use of HFCS has increased by more than 1,000 percent between 1970 and 1990, and this number is surely even higher today. American used to consume an average of 0.5 lb. of fructose a year, but this figure had already reached 62.4 lbs. a year in 1997.
Metabolic Syndrome
The metabolic syndrome, also called syndrome X, is characterized by a cluster of metabolic abnormalities. According to the National Cholesterol Education Program Adult Treatment Panel III, or NCEP/ATP III, the metabolic syndrome can be diagnosed when at least three of the following characteristics are present: abdominal obesity, which corresponds to a waist circumference of over 40 in. for men and over 35 in. for women, elevated triglycerides, low HDL cholesterol, high blood pressure and elevated fasting sugar levels.
Fructose
Fructose consumption has dramatically increased because of the increased consumption of sugar and foods sweetened with HFCS, such as soft drinks, desserts and other processed foods. Fruits, honey and agave syrup are also rich in fructose. Interestingly, fructose is not metabolized the same way as glucose. Fructose bypasses some important metabolic steps, which makes it easier to convert to triglycerides or fat when compared to other forms of sugar.
Fructose and Triglycerides Levels
Some studies compared the effects of providing 20 to 25 percent of the daily calorie intake as fructose or as glucose in participants for four to six weeks. The results showed that a high-fructose diet is associated with increased circulating levels of triglycerides, which is one of the symptoms of the metabolic syndrome, and higher "bad" LDL cholesterol levels, as reported in the "Journal of Nutrition."
Fructose, Body Weight and Insulin Resistance
Fructose, as opposed to glucose, does not stimulate the release of insulin. However, exposure to fructose over a long period can indirectly lead to insulin resistance, which is an underlying feature of the metabolic syndrome, as explained in "Nutrition & Metabolism." In addition to not stimulating the release of insulin, fructose is also associated with lower levels of leptin, an hormone produced by the fat cells to promote satiety. Low levels of leptin are associated with increased hunger and increased food consumption, which could explain the larger waist circumference of people consuming a lot of fructose and HFCS. Abdominal obesity is also associated with the metabolic syndrome.
References
- National Health Statistics Report: Prevalence of Metabolic Syndrome Among Adults
- University of Virginia Health System: Low Fructose Diet
- American Journal of Clinical Nutrition: Fructose, weight gain, and the insulin resistance syndrome
- Nutrition & Metabolism: Fructose, insulin resistance, and metabolic dyslipidemia
- Journal of Nutrition: Dietary Fructose and Glucose Differentially Affect Lipid and Glucose Homeostasi
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