Too Much Fructose May Skew Appetite Hormones

Consuming too much fructose — a form of sugar found in corn syrup, honey and fruit — appears to alter levels of hormones involved in appetite regulation in such a way as to encourage overeating, a new study suggests.

Consuming too much fructose — a form of sugar found in corn syrup, honey and fruit — appears to alter levels of hormones involved in appetite regulation in such a way as to encourage overeating, a new study suggests. After people in the study ate a meal followed by a drink flavored with the same amount of fructose found in two cans of soda, they showed relatively low levels of insulin and leptin, hormones that help people know that they are full. On the other hand, they showed relatively high levels of ghrelin, a hormone that stimulates eating. These hormonal changes “we think could promote overeating,” and subsequently obesity, study author Dr. Karen L. Teff told Reuters Health. Teff explained that sugar occurs in two forms, fructose and glucose. Glucose, but not fructose, stimulates insulin secretion, which in turn regulates leptin production. Both fructose and glucose are naturally found in fruit and fruit juices. However, over the years manufacturers have sweetened sodas and some foods with corn syrup, which contains concentrated amounts of fructose, she said. “If people are drinking five sodas a day, they’re getting a huge amount of calories, plus they’re getting a large amount of fructose,” she said. Based on these findings, Teff recommended that people limit their intake of soda and other drinks containing large amounts of fructose. “I’ve changed my eating patterns because of this, honestly,” she said in an interview. To investigate whether drinking fructose plays a role in obesity, Teff and her colleagues asked 12 normal-weight women to wash down balanced meals with drinks sweetened with either fructose or glucose. When the women drank the fructose drink, their levels of insulin and leptin were lower than when they consumed a drink flavored with glucose, and levels of ghrelin were higher, the researchers report in the Journal of Clinical Endocrinology and Metabolism. In addition, drinking the fructose drink was associated with a spike in levels of blood fats, a known risk factor for cardiovascular disease.Teff, who is based at the Monell Chemical Senses Center in Philadelphia, explained that drinking glucose-sweetened beverages may not encourage overeating as much as fructose drinks because glucose triggers insulin release from the pancreas, which tells people they are no longer hungry. Moreover, glucose is metabolized in a healthier way by the liver than fructose, she noted. Teff emphasized that there is no way to avoid fructose, which is a natural molecule. But drinking large amounts of it in soda, without any other nutrients, is not natural, she said. “I don’t think there’s anything wrong with (fructose), it’s just that people are drinking it in large quantities,” Teff noted. (Source: Reuters Health, Journal of Clinical Endocrinology and Metabolism, June 2004)