Monday, June 13, 2011

Glycemic Index Demystified

by Kris Pitcher

What is this glycemic index all about? GI? Am I supposed to eat low or high GI foods? Confused? Let's break it a sciency way. Oh, I'm getting exited!

All carbohydrates are not created equal. When we ingest carbohydrates our body breaks them down and begins to move them through our blood for use and storage (we're going to keep this simple). Our pancreas secretes insulin to help transport and store the carbohydrates - to hold its hand and move it into cells.

Some carbohydrates (simple carbs) need a lot of handholding. The Glycemic Index, GI, was developed as a rating system to determine how much handholding a carbohydrate needs. GI is a measure of the carbohydrate's effect on blood sugar levels.

Specifically it's the measurement of response (insulin response) in the two hours following eating 50 grams of the food. The standard against which foods are rated is white bread. White bread = 100 (GI rating). White bread's glucose effect - or blood sugar response = 140. So the GI is designed to estimate blood sugar response based on the GI rating of a carbohydrate.

Got it? This system was designed for diabetics, and it's been adopted by weight management communities as well because a steady blood sugar level is a marker of good food choices. A high GI rating is a fast digesting or simple carbohydrate, and a low GI rated food is a slower digesting carbohydrate.

Not so mysterious after all. GI indexed foods are categorized into 3 groups:

  1. Low GI: 55 or less - most fruits, vegetables, legumes, whole grains, nuts, & fructose 
  2. Medium GI: 56-69 - whole wheat products, batsmati rice, sweet potato, sucrose & lactose
  3. High GI 70-100 - baked potatoes, watermelon, white bread, white rice, breakfast cereals, glucose, maltose
The less a food effects our blood sugar, the less load it puts on our pancreas to secrete insulin to deal with it. We don't want to be eating foods that need a lot of handholding - we want to make choices from the low end.

Basically, the simpler a carbohydrate, the faster it's digested and gets into our blood stream. All of a sudden we have a dump into our blood, insulin has to rush in and grab it up (hold its hand) to transport it for storage.

Items on the low GI list digest slowly, they are like time-release carbohydrates. They are all grown up and need very little handholding. Just a little. Cause it's nice (wink).

Here's a list of 100+ foods and their glycemic index. I hope this helps to demystify the GI rating once and for all!

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