
Sugar is a complicated (and very important) topic that warrants a long-winded explanation. Here goes...
The first part of this post is all about what a sugar actually is. It will set you up for understanding sugar metabolism better. Its science-y, so bear with me while I nerd out on bonds and molecules.
To be clear, I will not be talking about artificial sweeteners here. Artificial sweeteners such as sucralose, aspartame, cyclamate, saccharin and sugar alcohols (sorbitol, xylitol) are chemically altered sugars that have a whole host of different health and metabolic implications.
All carbohydrates break down into simple sugar molecules. The most basic sugar molecules are glucose, fructose and galactose. Each of these molecules has the same chemical formula, C6H12O6, but they have slightly different shapes, which allows them to interact differently with the cells in your body.
In foods, sugars are combined with each other to make longer chains of carbohydrate.
- Sucrose is common table sugar = glucose + fructose
- Lactose is major sugar in milk = glucose + galactose
- Maltose is a product of starch digestion = glucose + glucose
Starch is made up of long chains of linked glucose. When they form a straight chain, it is called amylose. A highly branched glucose chain is called amylopectin, which is the chief energy storage unit in plants.
In animals a molecule similar to amylopectin is used to store energy. It is called glycogen. Glycogen has more frequent branches in its glucose chain than amylopectin.
Here is why all of this is important. When your body uses sugar for energy -- actually when it uses anything for energy -- it breaks it all the way down to carbon, oxygen and hydrogen atoms. The process of getting down to these tiny atoms is long and complicated, involving many enzymes and cellular checkpoints along the way.
The shape and size of the different sugars, as well as the way that the sugar molecules are linked to each other will directly affect what enzymes will break the sugar down, how quickly the sugar is broken down and how easily your body can use the sugar for energy.
All of these things affect your blood sugar. Blood sugar impacts insulin levels. Insulin, in turn, affects all of your other hormones including cortisol, leptin, glucagon, ghrelin, thyroid hormone and sex hormones. All of these hormones impact fat storage and metabolic rate.
How you metabolize sugars will also determine whether or not they cause an inflammatory response in the body. Certain sugars or products of sugar metabolism can cause oxidative damage in your body and inflammation.
How we determine if a sugar is ‘good’ or ‘bad’ is by looking at how the sugar impacts hormones, metabolism and if it does or does not cause oxidative damage and inflammation.
Phew! Did you get all that?
The Carbohydrate ‘F’ Word: Fructose
Before we get to fructose, we need to talk about a little bit about glucose first.
Glucose is one sugar molecule that pretty much everyone has heard about. Due to the dramatic rise in diabetes in our society, most people are familiar with the concept of blood sugar.
Glucose is important for the function of our bodies. It is an important component of energy production, especially for our brain, immune system and muscle tissue. When we do not eat enough glucose, our bodies will make glucose out of protein and fat. In order to function properly, our bodies carefully maintain a certain level of glucose in our blood. When this system, that maintains a healthy blood sugar level, is impaired, we call it diabetes.
Having too much sugar in the blood is bad because excess sugar can cause oxidative damage to the blood vessels.
Damaged blood vessels not only increase your chance of having a heart attack or stroke, they also deliver less blood to your organs, nerves and muscles.
This is why diabetics have decreased sensation in their hands and feet, weakness in the muscles, trouble fighting off infections and have a higher risk of problems with virtually every organ from glaucoma in the eyes to kidney failure, to liver disease and everything in between.
Since excess blood sugar is so damaging, the body works really had to keep sugar levels within a safe range. It does this by producing insulin.
Insulin is the hormone that signals your cells to take up glucose from the blood. It lets the cells know that there is energy in the blood that can be taken in.
The problem starts when you consume too much sugar all at once. Sugar enters the blood stream, insulin tells the cells that they have sugar available; the cells take up as much sugar as they need and then stop.
If there is glucose left over, it stays in the blood circulating. The brain knows this is a problem, because sugar is reactive and can cause damage, so it tells the pancreas to send more insulin. The insulin signals the cells to take up to glucose, but the cells are full.
Over time as this cycle continues, the cells start ‘listening’ to the insulin less and less. The pancreas produces more and more insulin every time you eat sugar. This state is called insulin resistance. Eventually, the pancreas cannot keep up with the demand of producing such massive amounts of insulin and it starts to fail.
So what does this have to do with fructose?
Fructose is unique in that the cells can use it for energy, but it does not need insulin to allow it to enter your cells. When you intake fructose it does not affect your insulin levels.
You might now be thinking: Great! So why not just put fructose instead of glucose in everything, then no one will get diabetes ever!
The problem with that theory (and researchers have tried it) is that the liver metabolizes fructose so that it is useable in the rest of the body. When you take in a lot of fructose, it is a huge burden on the liver and leads to liver damage and liver failure.
Here is the other problem with fructose. Most foods do not contain just fructose.
If you recall, sucrose, or table sugar, is 50% fructose and 50% glucose.
Since fructose is not dependant on insulin for use, when you eat fructose and glucose in combination, the glucose has an even harder time getting taken up by the cells because the fructose gets there first. This exacerbates the problem of insulin resistance… Which leads to all of the health problems that are associated with sugar consumption: chronic inflammation, obesity, diabetes and cardiovascular disease, to name a few.
For this reason, consuming large amounts of fructose, as is the case with high fructose corn syrup, can be catastrophic to your health.
So, what should you eat? Stay tuned for part two.
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