How to manage blood sugar levels

One reason we love sweet foods is the taste for sugar originally conferred major survival advantages on our ancestors. It enabled them to distinguish between edible and toxic substances (the sweet were likely to be edible, the bitter more toxic).

In a feast or famine environment, sweet foods supplied energy in a quickly accessible form. Unfortunately, we no longer live in a feast or famine environment, so this genetic urge doesn’t work so well. Today, we have too much of a good thing and the challenge is to help your body cope with the sugar assault.

Sugar is a general name for carbohydrates and there are literally thousands of different types of carbohydrates. There are the monosaccharides (glucose, fructose and galactose), the disaccharides (sucrose or table sugar, lactose or milk sugar, and malt, ferment from barley) and polysaccharides forming the starches, brans (cellulose) and glycogen.

Starches are broken down mainly to the monosaccharide glucose that we use for energy. Foods such as grains, vegetables, fruits, legumes, nuts and seeds provide complex carbohydrate, a wealth of nutrients and valuable fibre. Simple carbohydrates are found in sugar, honey, syrup, some components of fruit, white bread, refined foods, chocolate and lollies.

Cellulose (fibre) is an essential part of our diet, yet it’s considered a non-nutrient — in other words, we cannot digest it. What fibre does in humans, however, is absorb water, various toxins and the byproducts of digestion and excretes these in the stools. Fibre is also important to prevent constipation.

Carbohydrates are made of carbon, hydrogen and oxygen. They are the ideal dietary source of fuel for most body functions and their nutritional value varies over a wide range. Carbohydrates can be stored as sugars (glycogen) for short-term energy and the excess as fat for a long-term energy source. Glycogen is particularly stored in the liver and muscles. In a healthy person, the liver can store 8 per cent of its weight as glycogen.

The storage of large quantities of carbohydrates is inefficient, which means we need to eat them regularly. However, it’s the glycogen storage that enables you to get things done between meals. Without it, you wouldn’t be able to do anything except eat to maintain your energy. Fats are a much more efficient form of long-term energy storage, which is why all the macronutrients (carbohydrates, proteins and fats) are eventually stored as fat if you eat excessive amounts of food.

Hitting the wall

The body stores around 2000kcal of glycogen at any one time, so long-distance athletes have problems when, after extended periods of exertion, they go into glycogen debt. This is what’s called “hitting the wall” and the athlete experiences a sudden crippling fatigue. To prevent this, energy consumption must be kept up by regularly drinking high-carbohydrate drinks.

Absorption issues

When you eat carbohydrates, they’re broken down in the mouth and the small intestine. If you have problems digesting carbohydrates, you can suffer a range of symptoms, such as a feeling of fullness from bacterial fermentation, bloating, diarrhoea or constipation.

When carbohydrates are digested, they are then absorbed across the intestinal wall, which occurs at varying rates. The speed of absorption of the various carbohydrates has been categorised into a system called the glycaemic index, based on the absorption of glucose being 100. Simple sugars generally will be absorbed quickly but at different rates; some sugars, such as mannose and pentose (GI — 9), will absorb more slowly.

The speed of absorption and the metabolism of carbohydrates are critical factors in managing blood sugar levels, particularly today when conditions such as hypoglycaemia and adult onset diabetes are growing health issues. The slower the absorption of carbohydrates, the easier it is to control blood sugar levels and the less likely a person is to have problems with conditions such as hypoglycaemia or syndrome x (metabolic syndrome) or of developing diabetes. So low-GI foods are an important part of a good diet.

 

Sugar in your blood

Blood sugar levels are very closely controlled. Blood glucose levels have to stay in a reasonably constant condition or ill health (even coma and death) can result. There are several mechanisms that work together to maintain blood sugar levels within these very narrow limits. When you eat sugar/carbohydrates and your blood sugar levels rise, the pancreas releases insulin, which enables your body cells to take up glucose, removing it from the blood. Insulin also converts glucose into glycogen and stores it in the liver, and increases the use of glucose by the muscles when you exercise (for energy).

The glucose in the blood forms a complex with insulin. It is transported to the membranes of cells, where the insulin attaches to a receptor site called glucose tolerance factor (GTF — made of the amino acid glutamine, vitamin B3 and the mineral chromium). Once the insulin is attached to GTF, it releases glucose through the cell membrane and into the cell. The glucose is then broken down further as it passes through the cell (requiring B vitamins, magnesium and oxygen) and finally enters the mitochondria (or energy powerhouse of the cell), where it is converted into energy. There’s a range of nutrients required for this processing to proceed correctly (see below).

Balancing this, the hormone glucagon is also produced by the pancreas and does the opposite of insulin. It is released from the pancreas when blood sugar levels go down. This triggers the liver to then convert glycogen back into glucose to raise the blood sugar levels again.

There are many ways you can have trouble with managing blood sugar. Some people are particularly sensitive to sucrose (and other sugars), while others with poor liver function have poor glycogen storage; some will have low insulin production and others have excess insulin in the blood (particularly if they are low in chromium or GTF).