Fructose and Its Effects on Appetite
This is a study carried out at Yale Medical School. Researchers gave 20 adults a drink sweetened with glucose or one sweetened with fructose while their brains were scanned using magnetic resonance imaging. Interestingly, scans of adults sipping a glucose drink’s scan looked different from those drinking a fructose-sweetened drink. How so?
Subjects drinking the glucose drink had significantly less blood flow to regions of the brain like the hypothalamus that controls appetite and motivation to eat. The glucose beverage seemed to suppress activation of areas of the brain that make you want to eat (and overindulge) whereas the fructose beverage didn’t. In other words, the fructose beverage was less effective at turning off the desire to eat.
There were other negative effects of fructose-sweetened beverages in this study. They also failed to increase the levels of hormones that suppress appetite like insulin and GLP-1, a gut hormone that turns off appetite and reduces the desire to eat. Lower insulin levels may sound like a good thing, but insulin plays a key role in signaling satiety since it promotes the release of leptin, a key hormone produced by fat cells that promotes satiety. Although this is a small study, it confirms what some other studies show. Fructose may be less effective at promoting satiety than glucose.
Fructose also appears to be processed by the body differently. Glucose requires insulin to enter cells where it can be used or stored as fat. Fructose can’t readily enter cells but instead goes to the liver where it’s converted to triglycerides, the storage form of fat. This fat can accumulate, leading to fatty liver. Fructose consumption is also linked with high triglyceride levels, a risk factor for heart disease.
Table Sugar is a Mixture of Glucose and Fructose
You might assume that table sugar is better for you than high-fructose corn syrup based on this study. Not necessarily so. Table sugar or sucrose is a 50/50 mixture of glucose and fructose, so you’re getting fructose every time you add a tablespoon of sugar to a cup of coffee. High fructose corn syrup does contain slightly more fructose than table sugar but not by much. It’s about 55% fructose and 42% glucose with the remainder made up of other sweeteners. High-fructose corn syrup is made from corn syrup that’s modified by converting some of the glucose to fructose. You’re getting slightly more fructose when you consume high fructose corn syrup than with table sugar but the difference is small.
What Does This Mean?
The debate about the health risks of high-fructose corn syrup relative to sugar probably won’t be resolved any time soon, but based on the current research, it’s best to avoid fructose in any form in your diet – and that includes the fructose in table sugar. The best way to do that is to reduce the number of packaged and processed foods you eat since many contain high-fructose corn syrup or sugar.
What are the alternatives? If you sweeten your coffee, use a natural calorie-free sweetener like unprocessed Stevia or one of the new natural sweeteners made from Monk fruit in moderation. If you slowly taper back the amount of sweetener you use, your taste buds will adapt over several weeks and you’ll no longer crave the taste of overly sweet foods. It’s a move worth making – for the sake of your health.
References:
JAMA. January 2, 2013, Vol 309, No. 1.
Am J Clin Nutr October 2007 vol. 86 no. 4 895-896.
Harvard Medical Publications. “Abundance of fructose not good for the liver, heart”
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