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The Glycemic Index

I threw an impromptu poll out on the facebook fan page asking for a nutrition topic I could cover for this month’s newsletter.  I got some great responses ranging from supplementation to how to eat well during the holidays.  Since I recently wrote a four part series on supplementation and eating well during the holidays comes down to moderation and picking and choosing your food battles; I decided to go with the topic about the glycemic index.

I must admit I was a bit surprised that this topic was proposed because it seems like dieting trends come and go like the latest technology trends.  I remember when I first became interested in studying nutrition in the late 90s, the glycemic index was really popular and I searched bookstores and libraries to find out more information and get a copy of the glycemix index (GI) chart that classified and ranked foods according to the effect they had on the body.

Since then there have been numerous book and diets constructed around the GI system, but was this system just a trendy model from the late 90s or does the science still warrant merit from the health and fitness community?  In this article I will break down the GI system to see if indeed it should still be paid attention to in this day and age.

Simply Stated

According to The Gylecemic Index.com:

“The glycemic index or GI describes this difference by ranking carbohydrates according to their effect on our blood glucose levels. Choosing low GI carbs – the ones that produce only small fluctuations in our blood glucose and insulin levels – is the secret to long-term health reducing your risk of heart disease and diabetes and is the key to sustainable weight loss.”

When Carbohydrates (CHO) are digested and broken down by the body they will be reduced to their lowest structural components one of which is the sugar known as glucose.  In 1980 Dr. David J. Jenkins and colleagues at the University of Toronto conducted research to see how quickly different CHOs were broken down and released into the bloodstream.  Their research was based on the idea that CHOs which were broken down quickly during digestion released glucose into the bloodstream rapidly.  When glucose enters the bloodstream the hormone insulin is released by the body to take up the glucose and shuttle it to the liver and muscles of the body to be stored as glycogen which could be used for energy later on.  Foods that broke down quickly and caused rapid release of glucose into the bloodstream could pose health problems down the road if the practice of eating these types of foods was consistent.

Dr. Jenkins and colleagues conducted blood tests of their subjects to measure how quickly and how much glucose was found in the bloodstream after ingesting a particular CHO source.  They established a rating system and classified CHOs that were quickly broken down and released glucose rapidly as High GI foods and the ones that broke down at a gradual rate as Low GI foods.  Simply stated, high GI foods require high levels of insulin to be released.  If the system that releases insulin is perpetually working at a high rate, over time, the system will not be able to adequately handle the uptake of glucose for glycogen storage; therefore the glucose will remain in the bloodstream at high levels causing the disease known as Diabetes.

Eat This Don’t Eat That?

Before the internet blew up and you can find anything you wanted with a few taps of the keys, I searched several locations for the glycemic index chart.  I had a few family members that had cases of Type II diabetes (adult onset) and if these high glycemic foods were a leading cause of the disease I wanted to know which foods I should be eating and which would cause my blood sugar levels to go sky high.

After getting my eager hands on a chart and studying it for a bit I realized that rather than obsessing on what individual foods rate high on the chart, there is a simple pattern that can be followed.  Generally speaking, food sources such as fibrous fruits and vegetables had a low glycemic index, whole grain carbohydrates had medium GI responses and processed CHOs and simple sugars were high on the GI scale.  Without being overwhelmed with the GI effect we can simply think about which foods are natural, whole foods. Natural, whole foods are generally healthier and therefore they have a lower GI effect and a lower risk for diseases like diabetes and coronary heart disease.  When thinking about the glycemic index, the question becomes, is it as simple as don’t eat the foods that cause a high GI effect?  The answer might not be that simple.

First off, the GI significantly differs depending on a food’s current state and methods used during preparation and cooking.  Foods, like white potatoes, alter their GI number depending on its ripeness, processing, the length of storage, cooking methods.

Another factor to consider is that people are different and foods will have a different glycemic response from one person to another and even on the same person from day to day, depending on blood glucose levels, and insulin resistance.  Other factors like the current blood glucose levels, the amount of the particular food consumed, what a particular food was eaten in conjunction with, and fluid levels in the body can all result in different glycemic responses.

Scientists have taken note on some of the pitfalls of the GI ranking and tried to further expand on the ranking system by factoring in the amount of food eaten and the effects that can have.  The glycemic load (GL) is a ranking system for carbohydrates content in food portions based on their (GI) and the portion size. GL combines both the quality and quantity of a carbohydrate in one value.  This method is deemed superior to predict blood glucose values of different types and amounts of food.

Proponents of the GL state that high GI foods consumed in small quantities would give the same effect as larger quantities of a low GI foods on blood sugar; therefore it’s not only the type of food that you eat, it is the amount of food that you eat at a particular time.

How GI and GL Can Work For You

Now that I have even confused you more or made your brain hurt, let’s boil this down and make life simple. When considering all of these factors it may seem like the GI and GL are too difficult to understand and that there may not be a way to know what the exact effects are on your body.  I feel like understanding the basics can get you on the path towards optimal health.

Let’s first consider the GI.  Foods that produce a high GI effect in our bodies are, generally speaking, foods that are the simplest forms of carbohydrates that we already know to use sparingly in our diets.  White bread, white rice, honey and simple sugar are all considered high GI and they are simple CHOs devoid of fiber and many nutrients; we know that these foods should be only a small portion within our diets if we want to live a healthy life.

If you eat a food in its natural state the Gl will be lower

It is also simple to understand that the amount of food we eat effects how we feel.  Glycemic Load offers a little more insight, generally stating that high amount of foods consumed in one setting can have a high glycemic effect in our bodies.  Think about last week at the Thanksgiving dinner table; did we need to shovel that last bit of stuffing into our mouth?  Did we have to try every dessert on the table so our great Aunt would not be offended?  If you were like me then you did and you paid for it later with a bloated stomach.  Thank goodness I don’t do that quite often because the pains were a direct reminder that the GL was much larger than my body is used to; I probably raised my insulin levels to very high levels, and possibly added some fat around my belly.

When it comes to health and optimal performance it is good to have an awareness and general understanding of the different theories out there. With a little trial and error sprinkled in with some common sense, we can become in-tune to how our body optimally works and operates in accordance to the foods we eat and how we eat them.

Sources:

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Wednesday, December 1st, 2010 Nutrition
 

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