Once a humble and healthy fruit sugar, fructose now sits at the center of controversy thanks to its widespread consumption in the form of high fructose corn syrup. Since it doesn’t trigger the release of insulin, the sweetener was originally recommended for diabetics. Then, in 2006, the American Diabetes Association advised against using it. It turns out that the apparent benefit of reducing insulin is offset by fructose’s potential to increase fat and cholesterol.
Fructose is best known as the sugar in fruit, but it’s also found in honey and vegetables, especially starchy vegetables such as corn. Like other sugars, including table sugar, fructose has about 4 calories per gram and is quickly absorbed into your bloodstream. But it has some unique characteristics. It became a popular sweetener because it tastes sweeter than other sugars, so you can use less and get the same result. It’s also metabolized differently than other sugars. As a result, fructose doesn’t stimulate insulin secretion, according to the September 2010 issue of “Endocrinology and Metabolism.”
During digestion, most carbohydrates are broken down into the simple sugar glucose, which is vital because every cell in your body, including your brain, uses it for energy. Glucose can’t get inside cells unless insulin is available to help it cross the cell wall, so when glucose enters your bloodstream, your pancreas secretes insulin. Fructose doesn't stimulate the pancreas because it doesn't need insulin. It goes straight to the liver, where it enters a different metabolic pathway than glucose. An enzyme found only in the liver restructures fructose and determines its fate: fructose is converted directly into fat.
A sugar that inhibits the release of insulin sounds like a good thing because high levels of insulin can lead to Type 2 diabetes, but low levels of insulin can also cause problems. Insulin regulates hormones that influence metabolism. When you don’t release enough insulin, levels of the hormone leptin go down, which may make you feel hungry and slow down your metabolism. Add a slower metabolism to increased levels of fat from fructose, and you’re at a higher risk for putting on weight. Fructose also puts your heart health at risk, because it increases levels of cholesterol. As if that wasn't enough, fructose may still cause insulin resistance, which can lead to diabetes, according to Harvard Health Publications.
Natural Vs. Added
Naturally occurring fructose in fruits and vegetables does not cause health problems. The American Diabetes Association endorses consumption of fruits and fruit juices, as long as the juice does not have added sugar. The problem is that high fructose corn syrup is the primary sweetener in soft drinks, baked goods and other foods. Many people consume more fructose than they may realize. In 2008, the U.S. Department of Agriculture estimated that the per capita consumption of high fructose corn syrup was 11 teaspoons, or 179 calories, daily. Women should limit their consumption of added sugar to fewer than 6 teaspoons daily, while men shouldn’t exceed 9 teaspoons daily, notes the American Heart Association.