Simply Sunday – What is Glycemic Index?

Welcome to Simply Sunday here at the Health and Food Forum’s Blog.  In recent years, increasing attention has been focused on the glycemic index of foods in an attempt to decipher the “good” complex carbohydrates that should be included in your diet from the “bad” simple carbohydrates that should be limited or avoided.  Along with this greater awareness have come misunderstandings of the meaning of this reference tool, as well as some misuses.   Today’s Simply Sunday post will attempt to clear up any confusion regarding this matter.

Glycemic Index Definition: The measure of the affect a specific food has on your blood sugar (i.e., whether it causes a dramatic increase or an attenuated rise in your blood sugar).

How is the Glycemic Index Determined? Traditionally, the affect of pure glucose on blood sugar has been used as a reference to which the affects of other food sources are compared.  Glucose has been given the arbitrary value of 100.  Foods that are digested quickly and result in a dramatic rise in blood sugar are considered to have a high glycemic index; whereas, those foods that break down more slowly and have a less pronounced affect on blood sugar are categorized as having a low glycemic index.  Examples of high glycemic index foods include products such as white bread, refined breakfast cereals, and corn syrup.  Low glycemic index foods include such staples as beans and legumes, milk products, and whole-grain products.

Factors that Affect the Glycemic Index of a Specific Food:

  • The variety of the food (e.g., Red Delicious apple versus a Granny Smith apple).
  • Its degree of ripeness.
  • How it has been manufactured, prepared, and processed.
  • The amount of fat, protein, and fiber in its contents.
  • The type of sugar and starch present.
  • Eating a combination of foods at a time.
  • Physiological variances between people in their body’s response to the consumption of food.
  • Biological differences from day-to-day within the same person in response to the consumption of food.

Glycemic Index Uses

  • Weight management:  In general, individuals who consume greater amounts of high glycemic index foods tend to be heavier and have more body fat than those who consume less of these foods.  However, making the decision to eat a single food based on its glycemic index is not practical because foods are typically eaten in combination.  Therefore combining a high glycemic index food, such as honey, with a product that has a lower glycemic index, such as whole oats, could mediate the glycemic response.  Also, a food item can be characterized as having a low glycemic index but is not nutrient dense, and hence, may not be the best choice.  Furthermore, relying on the glycemic index of a food might lead to overconsumption of  calories due to the perception that “it is healthy so it is okay to eat more.”  Therefore, focus should be placed on total caloric intake relative to energy expenditure when weight control is the goal.
  • Diabetes Management:  Because high glycemic index foods lead to a greater rise in blood sugar, and hence, a greater demand for insulin, it is suggested that diabetics try to consume greater amounts of low glycemic index foods.  However, the amount of food that is consumed also affects blood sugar levels, so total caloric intake should be monitored as well.

Should High Glycemic Index Foods be Completely Avoided? No.  There are certain situations in which consuming readily digested and absorbed carbohydrates are necessary, such as after a bout of strenuous exercise when the body’s energy stores need to be replenished.

When it comes to deciding between consuming low- versus high glycemic index foods, balance is the key.  Eating a variety of foods, watching total caloric intake, and engaging in regular exercise is the best way to lead a healthy life.

Do you try to eat a balance of “good” and “bad” carbohydrates?  Share with us, we want to know!

Sources:

American Dietetic Association’s Complet Food and Nutrition Guide, 3rd edition, Duyff, R.L.

ACSM’s Fitness & Health, 6th edition, Sharkey, B.J.

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Filed under carbohydrates, glycemic index, high glycemic index, low glycemic index, simple carbohydrates

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