While some proponents say that high-fructose corn syrup is just like any other sweetener -- that when consumed in excess, it can cause weight gain, but it's no worse than other sugary additives -- several scientific studies beg to differ. High-fructose corn syrup may be associated with abnormal weight gain, increased blood lipid levels and leptin resistance -- a precursor to diabetes.
Some HFCS History
The two main types of high-fructose corn syrup added to processed foods today were introduced in 1967 and 1977, according to a review article in the Journal of Clinical Nutrition in 2004. But they now account for 40 percent of calorie-containing sweeteners added to the food supply in America. Because high-fructose corn syrup is significantly sweeter than sucrose -- or regular table sugar -- manufacturers can use less, making it more cost-effective. Soda is a major source of high-fructose corn syrup in the American diet, but the sweetener is also found in many other packaged foods, from ketchup to dairy products to jams and jellies.
In a study done by researchers at Princeton University and reported in Pharmacology, Biochemistry and Behavior in 2010, male rats were given either water sweetened with high-fructose corn syrup or water sweetened with sucrose in addition to their regular food. The water that was sweetened with sucrose had the same concentration of sweetener found in most commercial sodas, while the water that was sweetened with high-fructose corn syrup was only about half as sweet. After eight weeks, the researchers found that the rats who consumed the high-fructose corn syrup water gained significantly more weight than the rats given the sucrose water. The study shows that even less concentrated amounts of fructose can contribute to weight gain over a period of time.
Type of Fat
It’s not just weight that’s a cause for concern, however. In addition to increasing levels of body fats, the rats that drank high-fructose corn syrup water had increases in visceral fat -- the fat located deep within the midsection. High levels of visceral fat can increase the risk of type-2 diabetes, heart disease, high blood pressure, nonalcoholic fatty liver disease and certain types of cancer. These rats also had increased levels of triglycerides -- a type of fat in the blood that has been linked to an increased risk of heart disease.
Although it’s too early to say for sure, other studies have found that a diet high in high-fructose corn syrup may also increase the risk for leptin resistance -- a warning sign of diabetes. Leptin is a hormone that the fat cells in your body produce in response to hunger. When leptin is working correctly, its release tells your brain that you’re full and you don’t need to eat. In those with leptin resistance, the brain becomes desensitized to leptin. As a result, it's difficult to feel full, which can lead to overeating and weight gain. In a study published in the American Journal of Physiology - Regulatory, Integrative, Comparative Physiology in 2008, researchers reported that rats that were given fructose for six months and then fed a high-fat diet gained more weight than rats that weren't given fructose because of the development of leptin resistance.
High Blood Pressure
According to a study published in the Journal of the American Society of Nephrology, a high intake of fructose -- which researchers defined as more than 74 grams, or the equivalent of 2.5 soft drinks per day -- may also be associated with a greater risk for increased blood pressure in adults with no history of hypertension. It's important to note that this study did have a major limitation, though. The data was self-reported, so there was no way to confirm fructose intakes or the accuracy of reporting.