Glycemic Load and Glycemic Index

 
Glycemic Load Explained By Paula J. Wart
In the not too distant past, it was believed that foods containing sugar were “bad” because they caused blood sugar levels to rapidly escalate, whereas carbohydrates were “good” because their effect was more delayed.
 
Recently it’s been discovered that some foods release their sugar slowly, and other carbohydrate-containing foods have a “flash” effect on blood sugar levels.
Researchers began testing how quickly specific foods like beets and oatmeal convert to glucose (blood sugar), comparing them to white table sugar or white bread. They set a standard measure – how quickly will 50 grams of the particular food’s carbohydrates turn to sugar. That’s called Glycemic Index (GI).

 
What GI doesn’t tell you is how many carbohydrates are in a serving. This presents a problem. For example, you might think a cola soda pop, with a GI of 90 is better than cranberry juice because it has a GI of 105 (compared to white bread). You might be tempted to eliminate carrots from your diet due their extremely high GI value (131, using white bread as the base).

A More Detailed Explanation

Common sense tells you that a berry-based drink should be better than a sugar-based soda pop or that carrots have got to be good for you. That’s where Glycemic Load (GL) comes in: it takes into consideration a food’s Glycemic Index as well as the amount of carbohydrates per serving.
A carrot has only four grams of carbohydrate. To get 50 grams, you’d have to eat about a pound and a half of them (and who would do that except Bugs Bunny?).
GL takes the GI value and multiplies it by the actual number of carbohydrates in a serving; 131% x 4, devided by 100= 5
By contrast, a cup of cooked pasta has a GI of 71 and a whopping 40 grams of carbohydrates giving it a GL of 28.
Why we need to limit high G/I foods?

A high Glycemic food causes a sharp and a quick rise in blood glucose (sugar) which results in a sharp and quick rise in insulin. This is need to keep our blood Glucose with in normal range. Insulin open the door for glucose to get into the cells and out of the blood. Once in the cell, all glucose which is not used for energy is converted in to fat, in addition, insulin block the enzyme that brakes fat in to Free Fatty acids which can be utilized as an energy source and therefore causing farther fat storage.

What Determines GI and GL?
Since the values are based on carbohydrates, the values to a large degree are determined by how many grams there are per serving, and how quickly the carbohydrate is broken down into glucose. Several factors come into play:

  • Amount of cooking: Starches in food swell when cooked (whether it’s boiled, broiled, baked, or fried). The starch grains in a baked potato swell to the bursting point, whereas the starch grains in brown rice remain relatively unchanged.
  • Amount of processing: When grains are rolled, ground, or smashed, the protective (and harder to digest) outer coating is removed. Whole oats have a lower GI than oatmeal, which is made from smashed oat grains.
  • Amount of fiber: Some foods naturally have higher amounts of fiber – for example beans and legumes. Unprocessed foods (for example brown rice) have greater amounts of fiber than processed foods (white rice).
  • Amount of fat: The more fat there is in a food the longer it takes to digest. However, too much of the wrong kind of fat have been linked to a number of diseases, including heart disease, diabetes, and obesity.

 
GL values are interesting – and somewhat useful. But they’re available on a limited basis, and don’t take into account any valuable vitamins and minerals found in a particular food. To be healthy, get sufficient nutrients and fiber, and avoid a blood sugar “spike”:

  • Choose a wide variety of non-starchy vegetables
  • Replace refined foods with whole grain products
  • Eat fruits and starchy vegetables with high protein or high fiber foods
  • Use healthy fats – nuts, seeds, grains, fish, and liquid oils (olive, grape seed)
  • Lose weight (if you’re overweight)
  • Exercise regularly

 
Source:
1. Willett, W. Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. Simon & Schuster. 2001.

 

 

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