I have decided to take a little different approach to the video lecture “Sugar: The Bitter Truth“. Originally, I was going to write a summary, or the “tl;dtw” report (but now you have to watch it….muhahaha). However, I think my time would be better spent just detailing the sciency parts such as the comparison of fructose metabolism to that of sucrose and alcohol, and how fructose behaves (or misbehaves) in the body. That way you can really understand why fructose can do so much harm, and why it really behaves as a toxin. This post is just going to highlight fructose, while subsequent posts will discuss the differences between fructose and sucrose, fructose and alcohol, and other deleterious facts about this much loved poison.
Fructose: Why Its Metabolism Is Problematic
Two important facts to start off the the fructose discussion: fructose can ONLY be metabolized in the liver, and fructose does not stimulate the release of insulin. Glucose, on the other hand, can be metabolized anywhere in the body, and does facilitate the release insulin. Before I discuss the metabolism of fructose, I am going to point out a question in the video lecture. The lecturer asks this simple question: “What do we call it where when you take in a compound that is foreign to your body and only the liver can metabolize it, and in the process it generates various problems?” Answer: A poison.
Fructose Becomes Fat & LDL Cholesterol
First let me define a term: De Novo Lipogensis – a metabolic process in the liver that turns simple sugars into fatty acids, some of which are then changed into VLDL (a type of lipoprotein like LDL and HLD – and it’s bad stuff) so it can be secreted from the liver.
Some of the fructose in the liver undergoes this de novo lipogensis and becomes the free fatty acid palmitate. So your body just took in a sugar and made fat. This fatty acid is then turned into triglycerides, which are “re-packaged” as VLDL so they can leave the liver. Once this VLDL is in the blood, it can be stored as fat or turned into LDL. Not the “fluffy” larger LDL that isn’t associated with heart disease, but the small nasty LDL that IS associated with heart disease.
Fructose Can Lead To Hypertension & Gout
When fructose first enters the liver, a fructose specific enzyme (fructokinase) adds a phosphorous group onto the sugar. This phosphorous group comes from a molecule with 3 phosphorous groups, and when one is removed, the body then “rescues” the rest of the phosphorous groups off the molecule. This reaction culminates in the formation of the waste product uric acid (which is also secreted in your urine). Once the uric acid is released from the liver into the blood stream, it can cause gout and hypertension (by blocking your body’s natural blood pressure lowering system) if there is enough of it.
Fructose, Glycogen, and Athletes
Fructose is actually better for glycogen synthesis than glucose. This is great news if you need your glycogen stores replenished in your liver because this glycogen formation reaction takes precedence over the triglyceride forming reaction. This is why fructose is used in Gatorade. However, if your glycogen stores do not need replenishing because you haven’t been exercising recently, aren’t hungry, etc., the excess fructose is converted into triglycerides rather than glycogen.
It Doesn’t Stop Here (But It Does For This Post)
This is really just a simple introduction to fructose and the problems generated during its metabolism. Not only is additional research being published on other metabolic complications of fructose, but I haven’t discussed how the body behaves differently in response to fructose rather than glucose. Yes, the fructose rabbit hole IS that deep. Since I am really on a sugar/fructose learning kick, expect more…much more. :-)
