Fructose is a form of sugar found naturally in fruits and vegetables. It’s also a component of refined table sugar, or sucrose, which is half glucose and half fructose, and of high fructose corn syrup (HFCS), which has a ratio of 55% fructose to 42% glucose.
When it was discovered that fructose, unlike glucose, didn’t raise blood sugar levels or insulin and was significantly sweeter than glucose, it was hailed as a boon to all diabetics who could now satisfy a sweet tooth with impunity.
But then a dark side of fructose came to light. Scientists discovered that while the body can handle reasonable amounts of fructose from fruits and vegetables without serum fructose concentrations rising to dangerous levels, it can be overwhelmed by large quantities of fructose, especially refined (man-made) fructose.
Unfortunately, our steadily increasing consumption of refined sugar and HFCS seems to have done just that.
In the 19th century, average refined sugar consumption was about 7 pounds per year per person. We now average more than 150 pounds of sugar and HFCS per person annually, with sugar declining and the even more dangerous HFCS steadily increasing.
One problem associated with HFCS is obesity.
HFCS had been on the market for 34 years when renowned obesity researcher Dr. George A. Bray and colleagues suggested that consumption of HFCS in beverages could be driving the obesity epidemic.
Noting that the dramatic rise of obesity in the US since 1990 paralleled increasing use of HFCS, they explained how increasing fructose consumption could be causing people to gain weight.
Fructose is metabolized by the liver. Although the liver converts some fructose into glucose (the form the body uses for energy), the more fructose it’s asked to handle, the more the liver converts fructose into triglycerides and body fat, increasing weight gain (and heart disease risk).
Also, unlike glucose, fructose does not elicit the production of insulin. Insulin helps usher glucose into body cells, while fructose enters cells with another method. However insulin also stimulates the release of leptin, the hormone that signals “I’m full” to the brain. In addition, it suppresses ghrelin, the “I’m hungry” hormone.
Fructose neither increases leptin nor decreases ghrelin (a 2008 study showed it actually increased ghrelin). The result? You keep eating well after you’ve consumed the calories you need.
Dr. Bray also cited Danish researchers who observed that sweetened beverages tend to cause weight gain. Soft drinks today are generally sweetened with HFCS, and for some people, especially teenagers, soft drinks make up a large part of their diet.
More recent researchers have shown that both animals and humans with high fructose intake develop abdominal obesity. In fact when scientists need to create a model of abdominal obesity, they feed rats fructose for several weeks.
Whether or not HFCS is responsible for our obesity epidemic, it’s contributing to it and doing lots of additional damage as well. Studies link HFCS to high cholesterol and triglycerides, diabetes, glycation and accelerated aging, uric acid and gout, mineral imbalances and high blood pressure.
The simple fix: Cut out most processed foods, including health food store processed foods using the sweetener agave, another refined product. Be moderate in your fruit consumption (skip the juice and go for the whole fruit—we recommend two pieces a day), and treat yourself to something sweet on a special occasion only.
- Cozma AI. Effect of fructose on glycemic control in diabetes: a systematic review and meta-analysis of controlled feeding trials. Diabetes Care. 2012;35(7):1611-1620.
- Bray GA. Consumption of high fructose corn syrup in beverages may play a role in the epidemic of obesity. American Journal of Clinical Nutrition. April 2004;79(4): 537-543.
- Lindqvist A. Effects of sucrose, glucose and fructose on peripheral and central appetite signals. Regulatory Peptides. 2008 Oct 9;150(1-3):26-32.
- Rabin A. Sucrose compared with artificial sweeteners: different effects on ad libitum food intake & body weight after 10 wk of supplementation in overweight subjects. American Journal of Clinical Nutrition. 2002;76(4):721-29.
- Beigy M. Alternate-day fasting diet improves fructose-induced insulin resistance in mice. Journal of Animal Physiology and Animal Nutrition. January 2013;97(6):1125-1131.