Here is a fantastic article by Dana Carpenter on the glycemic load. You can sign up to her ezine by going to
http://www.holdthetoast.com.

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http://www.holdthetoast.com/archive/020116.html

Beyond the Glycemic Index

By now, many, if not most of you are familiar with the idea of the
glycemic index - the rating of how quickly and far any given
carbohydrate will push up your blood sugar. For those of you who are new to low carbing (congratulations on that New Year's Resolution!), here's a quick rundown of the concept:

The glycemic index, often abbreviated "G" or "GI" (as in, "low-G
carb" - I usually just call them "low impact" carbs) was first
explored as a way to control diabetes. For quite a while, scientists believed that simple carbohydrates, aka sugars, were absorbed quickly, and complex carbs, aka starches, were absorbed more slowly, and therefore were safer for diabetics, and would act as a far steadier supply of energy. Actual tests of the blood sugar impact of various carbohydrates showed this theory to be wildly simplistic, aka dead wrong.

Tests of the glycemic index were done thusly: A group of test
subjects was assembled, some of them diabetics, and some of them not. Their fasting blood sugar was tested. Then they were each given a carefully measured portion of the food to be tested. It is important to understand that these portions were measured to contain a specific amount of carbohydrate - 50 grams -- not a specific amount of the given food. In other words, the test subjects would eat about one and a half medium sized potatoes, or, or about 12 teaspoons of sugar, or a little over two cups of cherries - what ever amount of the food was needed to provide 50 grams of carbohydrate.

Once the subjects had eaten the test food, their blood was drawn at regular intervals for several hours, and their blood sugar tested, so that the researchers could observe how quickly it went up - and came down. These results were then averaged out between the test subjects, and that average was compared to the blood sugar impact of a "reference food". Originally the reference food was glucose, the most basic sugar, but some scientists eventually changed over to using standard, soft, puffy, grocery store white bread as the reference food, feeling that it had more real world significance. Whichever reference food they chose, it was given the rating of 100; the other foods were given a number which stood for how quickly or slowly that food raised blood sugar when compared to the reference food.

(Good to know: When glucose is used as the reference food, white bread is about a 70, and glucose ends up being something like 130 or 140. If you're consulting a chart of glycemic indices, it's important to know which reference food they're using, or you won't fully understand the numbers.)

These tests of the glycemic index made it clear that the old idea of sugar = fast, starch = slow was erroneous. There were lots of
surprises - for instance, the fact that baked potatoes will jack
blood sugar around faster and harder than an equivalent amount of table sugar (although, of course, the potato will also contain more vitamins.) It was found that whole wheat loaf bread is nearly as hard on blood sugar as white bread, but for some odd reason whole wheat pita bread has a far more modest impact. We also learned - thank heaven! - that rice cakes, the dieter's penance, nasty, styrofoam-like things that they are, have a sky-high glycemic index, and can't be considered health food by any stretch of the imagination.

(Do you know what food has perhaps the highest glycemic index of any tested, with a heavier-duty blood sugar impact than pure glucose? Tofutti, the tofu "ice cream" sold in health food stores. On the glucose scale, it's a 115, while really-truly ice cream is only a 61.)

Several things appear to influence the blood sugar impact of
carbohydrate foods. Fiber is one - the higher the fiber content, in
general, the lower the glycemic index, apparently because fiber holds the digestible carbs you eat like a sponge, time releasing them into your blood stream. This may well account for quite a lot of the research showing that eating a high fiber diet is healthy; by eating a lot of fiber one may moderate some of the bad health effects that come with the blood sugar roller coaster.

Degree of processing also makes a difference; eating whole boiled wheat kernels is easier on your blood sugar than eating coarse-ground wheat bread, which in turn is easier on your blood sugar than eating puffed wheat.

Perhaps most controversial, we learned that some fruits and
vegetables had a higher glycemic index than anyone had previously suspected. In particular, carrots were found to have a high glycemic index, and for that reason, many low carb dieters avoid them like poison, to the point of picking little bitty shreds of carrot out of their salads.

Remember the point I made several paragraphs back, that it was
important to understand that the glycemic index tests involved eating whatever sized portion of the test food was needed to make up 50 grams of carbohydrate? This is the weakness of the whole concept.

Because of this particular point, some foods were made to appear taboo for the carbohydrate intolerant, when in reality, they could be tolerated in the sort of quantity that people generally eat them.

Carrots, it turns out, are a case in point. It is apparently true
that eating enough carrots to consume 50 grams of carbohydrate will jack your blood sugar around pretty good, but do you know how many carrots that is? More than fifty of those little baby carrots, that's how many. I don't know about you, but I don't like carrots that well!

In other words, while a half a cup of carrots contains more, and
higher-G, carbohydrate than, say, a half a cup of cucumber, they're not something we have to shun altogether. For instance, I made a pot of soup yesterday, and I included, among other vegetables, one sliced carrot. Assuming that we call the whole potful 6 servings, that carrot added a bit less than a gram of usable carbohydrate to each serving, and it surely improved the flavor, and the vitamin content.

Enter the concept of the glycemic load.

"Glycemic load" is a new way of using those glycemic index tables to make them apply more realistically to food as people actually eat it. To calculate the glycemic load of a given food, you simply multiply the glycemic index of the food (using the white bread scale) by the number of grams of carbohydrate that are actually found in an average serving of that food. For instance: the glycemic index of soft drinks is about 97. There are about 42 grams of carbohydrate in a twelve ounce can of soda. 97x42 = 4,074, or something you really don't want to touch. Pumpernickel bread has a glycemic index of 71, and about 16 grams of carbohydrate per slice. 71x16 = 1,136; still pretty heavy
duty. But while cooked carrots have a glycemic index of 56, a half-
cup serving has only about 8.2 grams of carbohydrate - 56x8.2 =
459.2, or nowhere near as scary as either of our other examples.

(I should point out here that, for some reason that no one has
explained to me, these values are actually expressed with the decimal point in a different place: the glycemic load of soda would be expressed as 40.74, pumpernickel as 11.36, and carrots as 4.59.)

You can see the usefulness of this concept - it gives us a real-world idea of what various foods are likely to do to our blood sugar, and our bodies. It is interesting to note that the Harvard Nurses Study has looked at the glycemic load of the diets of the participants, and has found that the risk of heart disease goes up with an increasing glycemic load. This, of course, will come as no great surprise to those of you who have seen a rapid and marked improvement in your bloodwork since going low carb.

Please keep in mind that none of this can tell you how much
carbohydrate is appropriate for your own personal body. I know that I gain weight if I eat too much carbohydrate, regardless of the source.

If you need to stay below, say, 60 grams a day, you need to stay
below 60 grams a day, and the fact that those carbs have a more
modest blood sugar impact won't keep you from gaining weight.
Conversely, by sharply cutting your carb intake you are dramatically reducing your glycemic load, even if you were to get all of your very few grams of carb from sources with a high impact.

However, there is little question that you will do yourself a favor
by choosing what few carbs you do eat, by and large, from those with a modest glycemic index. And the day may not be too far off when officialdom scraps the dangerous food pyramid, and instead hands out daily glycemic load guidelines, and a big improvement it would be, too.

Indeed, the most encouraging thing to me about all this research on the importance of glycemic load is that the whole concept of limiting carbohydrate intake for health is becoming more and more accepted in the medical community.

For the most extensive list of glycemic indices I've been able to
find, look here: http://www.mendosa.com/gilists.htm This gives the rating both on the glucose scale and the white bread scale. To calculate glycemic load from these ratings, multiply the white bread scale number of the food in question by the number of grams of carb in a serving.

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