Storing Glucose

Why does my doctor say I can't have sugar in my coffee any more, but tells me to eat pasta, rice and starchy foods. Isn't starch another form of sugar?

That's the question I asked my doctor and when he just kept repeating "You need carbohydrate in your diet" over and over, I realised he really didn't have an answer at all.

Since then I have discussed this with two dieticians as well as other doctors and received the same response. While they agreed that carbohydrate was a stored form of glucose and was digested (broken down) into glucose. They even agreed that it should be more effective to reduce starchy foods rather than sugar but no-one could explain why the medical profession did not teach this.

There are many different types of starch molecules, all made up of glucose molecules packed tightly in a spring or helix formation. The simplest starch molecule breaks down into 22 glucose molecules, whereas one sugar (sucrose) molecule breaks down into only 6 glucose molecules and it's glucose that our bodies store as fat, so doesn't it make more sense to reduce starch, than sugar?

Here, in simple terms, I will take you through the basic role of glucose, how it is created, stored, consumed and how the excess is processed in our metabolism.

Glucose
The energy store for both plants and humans.

1. Creating Glucose
Lets begin with the plants, since they are the begining of the food chain.

Using the energy from sunlight, plants turn carbon dioxide (CO2) and water (H2O)into glucose, in a process called Photosynthesis. To keep it simple, we won't go into the chemistry here.

The process releases oxygen back into the atmosphere. Glucose and Oxygen are the fuel for all plant cells. Below is a single glucose molecule. Notice it is only made up of C's (Carbon), O's (Oxygen) and H's (Hydrogen) - the same elements in water (H2O) and carbon dioxide (CO2).

2. Creating Starch
Plants make an excess of glucose on sunny days which they need to store for night time and winter, when there is less sunlight. They do this by chaining glucose molecules together either in long strings or complex networks. This more complex molecule is very compact so is an ideal energy store for plants. It's called starch. There are many different types of starch, depending how the glucose are linked to each other. Below is a simple section of a starch molecule, showing 4 glucose molecules linked end to end.

When the plant runs low on glucose, special enzymes, (called amylase), split off glucose molecules from the starch molecule.

Mouse over the picture below to see how this is done.

In this case the starch molecule forms a spiral as more glucose molecules are added. It becomes like a tightly wound spring. A single starch molecule may contain from 22 glucose molecules up to thousands, depending on the type of starch.

3. Digesting starch into Glucose
We eat the plant cells as fruits, nuts, grains or vegetables and digest the starch. In our saliva is the enzyme alpha-amylase, which we mix with the food when we chew it. It starts breaking down the starches in our food, into glucose or other more complex sugars which will be broken down into glucose later in the gut, where the pancreas adds more amylase enzymes to the food.

4. Storing Glucose
Unlike plants, animals cannot make starch to store glucose. When there is an excess of glucose they use a different method. They convert glucose into fats.

5. Common Sense says . . .
Lets use one of the smallest starch molecules - a chain of only 22 glucose molecules - for this example.

If I digest one sucrose molecule (scientific name for sugar), it will create 6 glucose molecules.

If I digest one starch molecule, it will create at least 22 glucose molecules (remember we chose the simplest starch molecule - we could normally be talking about thousands of glucose molecules!)

It's not rocket science - cutting back on starch rich foods is far more effective in reducing glucose than cutting back on sugar - at least three times more effective. Since excess glucose is stored as fat - it will also be more effective for weight loss too.

6. What are the high starch foods?
Flour is the most concentrated form of starch we usually eat, so cut back all flour based foods like breads, cakes, biscuits, pies, pancakes, scones etc. These are the worst because the starch is highly processed and readily digestable.

Other high starch foods are rice, potatoes, sago, tapioca, polenta and pasta.

Cut your intake of these foods by at least half - our modern diet has too many starchy foods.

I can't help wonder, when we hear about the war on obesity and how they tell us to avoid eationg fats, salty food and food with lots of sugar, why don't they also tell us to cut back on high starch foods too?

When you look on all the dietry information that shows your ideal dietry intake, there at the base of the dietry pyramid are the foods we are told to eat most, is all the starch rich foods.

The food pyramid according to the medical profession today.

Notice the starches at the bottom - the foods we are told to eat most of. Not much has changed - here's one from a 1950's Health Education Poster.

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