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Glucose Trumps Fructose

When my friend Joe Anderson told me a couple of years ago that he prefers glucose to fructose, I thought he was nuts. After all, glucose has a glycemic index of 103, while that of fructose is only 15.

I had never seen a scientific study showing that using fructose was worse for us than using glucose. I have now.

A study team led by Karen Teff, Ph.D., of the Monell Chemical Senses Center in Philadelphia reported its findings a few days ago in the Journal of Clinical Endocrinology and Metabolism. The Monell Center sent me a copy of the full text of the study, “Endocrine and metabolic effects of consuming fructose- and glucose-sweetened beverages with meals in obese men and women: influence of insulin resistance on plasma triglyceride responses.” The abstract is free online.

The report points out that a fundamental difference between fructose and glucose is that the liver metabolizes fructose. On the other hand, our body converts glucose to energy when our pancreas releases insulin. That mops up the glucose and carries it the the cells that need it.

“Fructose metabolism is relatively unregulated,” the report says, while a rate-limiting enzyme controls the release of glucose. Consequently, taking in lots of fructose leads to increased production of very low-density lipoprotein and triacylglycerides. Furthermore, fructose promotes lipogenesis, which converts carbohydrates or protein to fat.

Basically, what they found was that when obese people drink fructose-sweetened beverages with their meals their triglyceride level goes up a lot, while glucose-sweetened beverages has only a moderate impact. The total amount of triglycerides over a 24-hour period was almost 200 percent higher when they drank fructose-sweetened beverages.

The effect of the fructose on triglycerides was even stronger among the people in the study group who were insulin-resistant. The study noted that insulin resistance is a pre-diabetic condition often associated with obesity. But we know that insulin resistance is not just a pre-diabetic condition. Type 2 diabetes develops from the combination of insulin resistance and beta-cell dysfunction.

This fact makes the new research directly relevant to those of us with type 2 diabetes. This means that fructose increases our risk for heart disease.

“Increased triglycerides after a meal are known predictors of cardiovascular disease,” Dr. Teff said. She is a metabolic physiologist with a Ph.D. in experimental medicine from McGill University in Montreal.

Our body makes triglycerides from dietary fat. They are the most common form of fat that the blood transports. High levels of triglycerides are associated with increased risk for atherosclerosis and other predictors of cardiovascular disease.

In the study Dr. Teff and her collaborators studied 17 obese men and women. I wish they had studied more people, but their research is continuing.

In the study the study group got identical meals except for the sweetener used in the beverages that accompanied their food. At one time in the study their beverages were sweetened with glucose and at another time with fructose.

If you scrupulously avoid high fructose corn syrup and use nothing but table sugar (sucrose), you might think the study doesn’t apply to you. Unfortunately, however, sucrose is half fructose — the bad sugar. The other half of sucrose is glucose, which we can now call the good sugar.

This article is based on an earlier version of my article published by HealthCentral.

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  • Penny F. at

    I have been diognosed with High Triglycerides, and hypothyroidism. My Hdl and Ldl are good and my blood pressure is excellent. I am 52 years old and trying to figure out what this all means. Should I then avoid Fructoise and allow gluccose in my diet?

    • David Mendosa at

      Dear Penny,

      You definitely should avoid table sugar and high-fructose corn syrup in your diet. That’s worst. But glucose is bad too; best to minimize it.


  • David Mendosa at

    Dear Colin,

    Thanks for asking. The answer is defintely no. Avocados are one of the best fruits, in part because of the type of fat that predominates (monounsaturated). They have no fructose either. Green peppers (actually a fruit, although many people think of them as a vegetable) have little fructose and provide excellent nutrition, as do lemons and limes.

    Best regards,


  • Colin Eblen at

    Should one avoid fruits in general??