Carbohydrates used to be (prior to the 1980’s) classed only as “simple
” (sugars) -- or “complex
” (starches) and it was thought all sugars would raise your blood sugar far faster than any starches.
In 1981, Dr. David Jenkins developed a new system for looking at carbohydrates and the impact they have on blood sugar. He called his method the Glycemic Index (GI)
and this has now become the standard against which carbohydrates are measured. Dr. Jenkins had volunteers eat different foods, each containing 50 grams of useable or available carbohydrates (net carbs, after deducting the amount of fibre which is not digested), and then measured each individual’s blood sugar level numerous times over the next two hours to see what happened. Pure glucose (which is the form of sugar indentical to blood sugar was used as a control and given the number of 100. The test food was then assigned a GI depending on how it raised the blood sugar as compared to the glucose control. The GI measures the blood sugar raising “quality” of the food. A GI of 55 or less is considered low; 56 to 69 is moderate; 70 or more is high.
If there was a flaw in the GI findings it was the fact that the GI is based on 50 grams of net carb of each food
. For example -- Jelly Beans
have a GI of 78
. We all know they are almost straight sugar and not exactly a health food; especially if compared to a nice hunk of watermelon or similar fruit. Well, Watermelon
has a GI of 76
Hence the Glycemic Load (GL)
was developed. The GL is simply a mathematical way to equate the GI to normal serving sizes – the formula is GI x net carb in the serving size / 100. Back to the jelly beans and the watermelon. For the JBs
, the serving size was determined to be about 1 oz (that’s not a lot; most people want more) and the GL is 22
. For the Watermelon
, a serving size is about 1.5 cups of cubes (and that’s a good amount for most of us) and the GL is 9.
Which do you think would be more filling? The GL considers both “quality” and “quantity”. A GL of 10 or less is low; 11 to 19 is moderate; 20 or more is high
Tomorrow – Apples and Avacodos
– the first of our Magic Foods - finally she's actually going to talk about food