Apr 13, 2011

is sugar toxic?

A new article in the NY Times by my favorite health write, Gary Taubes. There isn't much new in here. Sugar is bad. But it does reference an endocrinologist at the University of California, SF. He treats obese kids. And more importantly there is a link to a YouTube video of a talk he gives. It's an interesting talk. He does get some things wrong that aren't worth going into. It's better to focus on the stuff he knows well. Metabolic pathways. He goes through, in a not so great manner, the metabolic pathways of glucose, ethanol, and fructose. It's not riveting because he throws out too many big words and processes without explaining them. It almost comes off like he's showing off and treating his audience like they'll never get it. But if you can follow along at a high level he describes what happens to these three compounds as they are processed in the body and the effects it has on the body. In particular he believes fructose is bad and he does a good job of demonstrating why this is. He goes easy on glucose but his story is incomplete because he doesn't follow all the pathways of glucose. Just the ones in the liver. But glucose is processed in the entire body.  But that is fine if we just focus on why fructose is bad.

Remember sugar is 50% glucose and 50% fructose.  In most fruits the sugar content is close to that although there are fruits with much more fructose and much less fructose than that.

Here's what fructose does at the metabolic level
  1. Fructose doesn't stimulate leptin production due to production of JNK1 - the hormone that gives us the feeling of being full. Even worse it reduces the brain's ability to perceive the presence of leptin
  2. Fructose doesn't suppress ghrelin - the hormone that stimulates hunger
  3. Fructose leads to significant production of LDL compared to other foods. Not just any LDL. A specific bad, dense form of LDL, VLDL. The one that really leads heart disease.
  4. Fructose is sweeter than sucrose so it tastes good, yet we don't use less of it when substituting
  5. Uses up phostphates in ATP. This ultimately leads to the creation of uric acid which leads to hypertension (high blood pressure) and gout (both of which have been on the rise over the last 30 years)
  6. Produces Xylose 5-P which ultimately activates the three fat making enzymes and will send your triglycerides through the roof and increases free fatty acid production which leads to insulin resistance

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