Some say they’re the greatest thing since sliced bread others feel they’re the scourge of the dietary world. How can something that’s natural, wholesome, readily available and economical cause so much controversy? By now you’ve probably heard of the Glycemic Index.
The Glycemic index (GI) is a measure of how carbohydrate-containing foods affect blood glucose levels. All foods that contain carbohydrates, such as starchy vegetables (potatoes, corn), desserts, fruits, bread, pasta, and rice, can be tested for how they affect blood sugar levels after being eaten. That still leaves many scratching their heads and thinking “a banana is a fruit so what’s the big deal?” The nutritional values only serve to widen the chasm of good vs. bad.
- Serving size = 1 medium sufficiently ripe banana ,about 7″ long
- Total Fat = 0 g; Cholesterol = 0 g; Calories = 110
- Potassium = 400 mg (10% of daily recommended value)
- Dietary Fiber = 4 g (16% of daily recommended value)
- Sugar = 14.8 g; Protein = 1 g (2% of daily recommended value)
- Vitamin C = 16% of daily recommended value
- Vitamin B6 = 20% of daily recommended value
Ok, let’s get down to the nitty gritty of the GI controversy. When a food is eaten, its digestible carbohydrates are converted to glucose by the body to provide energy for cellular function. Glucose released from the digested carbohydrates also causes the pancreas to secrete insulin, which promotes absorption of the glucose by muscle, fat and other cells. But some carbohydrates in food are digested and converted to glucose faster than others convert. To account for differences in how rapidly carbohydrates in different foods are digested, and subsequently release glucose into the blood stream, scientists have ranked foods according to their “glycemic index.” So far so good, let’s keep going.
While the glycemic index gives an indication of how a food will affect blood glucose, it is based on the amount of the food that provides 50 grams of carbohydrate, and not on the amount of available carbohydrate present in a normal serving of that food. The concept of glycemic load was introduced by scientists at Harvard University to correct for the effect of serving size on the glycemic index, because not all serving sizes of a food contain 50 grams of available carbohydrate.
Glycemic load is defined as the glycemic index of a food, times the amount of available carbohydrate in the food, divided by 100. Foods having a high glycemic load cause blood glucose levels and insulin to rise faster and higher than foods having a low glycemic load. Furthermore, the spike in insulin release caused by high glycemic load leads to a rapid decline in blood glucose, which in turn causes a feeling of hunger and the need to eat. In addition to the undesirable effect that high glycemic load has on blood glucose and insulin release, the long-term consumption of foods having high glycemic loads is a predictor of risk for developing type 2 diabetes and heart disease.
All of this means that one should eat foods having low glycemic load. So how about that banana? A banana has a glycemic index of 52 and 24 grams of available carbohydrate. This gives a glycemic load of 12. In comparison, an apple having a glycemic index of 38 and 15 grams of available carbohydrate has a glycemic load of six. Although an apple may be a little better choice for a snack, eating a banana isn’t all that bad either because foods with glycemic loads in the low teens and below are the ones that should be selected as part of a balanced diet.
Generally, fruits, non-starchy vegetables, nuts and legumes have desirable glycemic loads. Their sugars enter the blood stream gradually and trigger only a modest release of insulin. In considering low carbohydrate diets, it is important to remember that even though fruits, vegetables, beans and nuts contain carbohydrates, they also contain important vitamins, minerals and fiber. Removing these foods from your diet to achieve low carbohydrate intake also means that you are reducing your intake of important, essential nutrients. Although foods having high glycemic loads should be eaten infrequently, foods with glycemic loads in the low teens and below contain “good carbohydrates” along with other important nutrients and should be part of a healthy diet. The glycemic loads for many foods are available on the internet and finding a “good carbohydrate” is as easy as typing either glycemic load or glycemic index into your search engine.
“U. S. Department of Agriculture”
As with everything else Fitbuddies, the choice is up to you. And I’ll say it as many times as I have to it’s also about balance and moderation. Find out what works best for your body.