How Blood Glucose Works

In simple terms, for the sake of our health, blood-glucose levels need to remain within certain levels. The body regulates these blood sugar levels using two mechanisms: hunger and insulin.

* When blood-glucose levels fall, the brain causes us to feel hungry. Result? We eat food that is converted into glucose and our blood sugar levels rise. If we don't eat and blood-glucose levels fall too low, we trigger the condition known as hypoglycemia.

* When our blood-glucose levels rise, the brain tells our pancreas to release insulin. Result? The insulin helps to disperse the glucose and our blood sugar levels fall. Without insulin to regulate a rise in blood-glucose, the amount of sugar in our bloodstream can become toxic, triggering the condition known as hyperglycemia.

Effect of Carbohydrate Foods on Blood Glucose Levels

When carbs are eaten and digested, they are converted to glucose and enter the bloodstream where they raise blood-glucose levels. How fast these carbs raise blood-sugar levels depends on their glycemic index value.

* Individual carb-containing foods or (more commonly) carb-containing meals with a high glycemic index value cause a "spike" in blood-glucose levels. Meaning, our blood-sugar rises very fast, triggering an equally rapid response from the pancreatic gland which pumps out enough insulin to deal with the excess blood sugar. Result? Within an hour or so, the large secretion of insulin has dispersed all the excess blood glucose and then some. So we feel hungry again!!

* Individual carb-containing foods or carb-containing meals with a low glycemic index value raise blood-glucose levels in a slower more sustained manner. So the pancreas responds by releasing a more moderate amount of insulin. Result? Hunger is kept at bay and we feel satisfied for longer.

The glycemic index

The glycemic index,is a new system for classifying carbohydrate-containing foods, according to how fast they raise blood-sugar levels inside the body. In simple terms, a food with a higher glycemic value raises blood sugar faster and is less beneficial to blood-sugar control than a food which scores lower.

The glycemic index consists of a scale from 1 to 100, indicating the rate at which 50 grams of carbohydrate in a particular food is absorbed into the bloodstream as blood-sugar. Glucose itself is used as the main reference point and is rated 100.

The glycemic index separates carb-containing foods into three general categories: (1) High Glycemic Index Foods (GI 70+), that cause a rapid rise in blood-glucose levels. (2) Intermediate Glycemic Index Foods (GI 55-69) causing a medium rise in blood-glucose. (3) Low Glycemic Index Foods (GI 54 or less), causing a slower rise in blood-sugar.

The Drawback of the Glycemic Index

Glycemic index tests are not performed on typical portion sizes. So, by using the Glycemic Index alone, the glycemic effects of foods containing a small percentage of carbs are likely to be overstated, while the glycemic effects of foods containing a high percentage of carbs are likely to be understated. For example, foods that are mostly water or air will not cause a surge in your blood sugar levels even if their glycemic index is high.

This is why scientists developed the idea of Glycemic Load. It ranks foods according to actual carb content (eg. in a typical portion-size), not how fast a 50g amount of carbs raises blood sugar levels.

Glycemic load tells you how much carbohydrate is in a standard serving size of food. To calculate glycemic load in a typical serving of food, divide the GI of that food by 100 and multiply this by the useable carbohydrate content (in grams) in the serving size. For example, the glycemic index of carrots is about 47. Carrots contain about 7 grams of carbohydrate per 100g of carrots. So, to calculate the glycemic load for a standard 50g serving of carrots, divide 47 by 100 (0.47) and multiply by 3.5. The glycemic load (GL) of carrots is therefore 1.6.

Type of Food in a GI Diet

A healthy GI diet is based on foods with a lower GI value. Typically, GI diets are low in fat (30 percent of calories) with an emphasis on monounsaturates and polyunsaturated essential fatty acids, moderate in protein (about 20 percent of calories), and contain about 50 percent of calories from carbs, with an emphasis on high fiber whole grains.

Types of Carbohydrate in a GI Diet

A healthy GI diet typically includes plenty of fruit (eg. apples, citrus fruits, berries), plenty of non-starchy and green leafy vegetables, regular servings of beans, peas and lentils (low GI and high in soluble and insoluble fiber), oily fish, lean meat, regular servings of starches such as dense chewy breads (whole grain, whole wheat, composed of stone-ground flour where possible), controlled portions of pasta, brown or basmati rice, eggs, lower-fat dairy foods, nuts and seeds.

GI Diets Advocate Eating Little and Often

A healthy GI diet typically recommends eating several meals/snacks throughout the day. This helps to maintain stable blood glucose levels and reduces food cravings that encourage overeating or sudden binges. Eating little and often also helps to maintain an efficient metabolism, so you burn calories at an optimal rate. All these benefits of a GI diet make it easier to lose weight.

Exercise Helps to Keep Blood Glucose Stable

A healthy GI diet plan always advises regular exercise. Physical exercise helps to reduce blood sugar in the bloodstream.

Carbohydrate-rich foods like vegetables, fruits, beans and wholegrains are highly nutritious. Such nutrient-dense foods keep us healthy and thus assist weight management - remember, a healthy body loses weight faster. And by selecting only lower-GI carbs, GI diets ensure that you obtain all your important nutrients without incurring the metabolic and digestive health problems associated with refined "Western" carbohydrates.