Friday, April 9, 2010

The huge gap between glycemic loads of refined and unrefined carbohydrate-rich foods

I often refer to foods rich in refined carbohydrates in this blog as among the most disease-promoting agents of modern diets. Yet, when one looks at the glycemic indices of foods rich in refined and unrefined carbohydrates, they are not all that different.

The glycemic index of a carbohydrate-rich food reflects how quickly the food is digested and generate a blood glucose response. Technically, it is measured as the area under a two-hour blood glucose response curve following the consumption of a portion of the food with a fixed amount of carbohydrates.

A measure that reflects much better the underlying difference between foods rich in refined and unrefined carbohydrates is the glycemic load, which is the product of the glycemic index of a food by the carbohydrate content in a 100 g portion of the food.

The glycemic load is also the reason for one known fact among diabetics. If a diabetic person eats a very small amount of a high glycemic index food, he or she will have a relatively small increase in blood sugar. If that person consumes a large amount of the same food, the increase in blood sugar will be dramatic.

The table below (click on it to enlarge) shows the remarkable differences between the glycemic loads of foods rich in refined and unrefined carbohydrates. It was taken from an article co-authored by Loren Cordain, Michael R. Eades, and Mary D. Eades (full reference at the end of this post).

At the time of this post’s writing, the article from which the table above was taken had a solid number of citations to it; a total of 74 citations on Google Scholar’s database. It is an excellent article, which I highly recommend reading in full (the link to the online full text is at the end of this post).

What is the reason for the differences in glycemic loads?

The answer is that foods rich in unrefined carbohydrates, even those with a high glycemic index (such as potatoes), are also packed with a number of other things – e.g., micronutrients, fiber, water, and even some protein. An Irish (white) potato is 75 percent water. By comparison, cereal, without milk added, is about 1 percent water. You have to add a lot of whole milk to it to make it a bit healthier. And even unsweetened whole milk is about 5 percent sugar.

There was nothing even remotely similar to modern foods rich in refined carbohydrates in the diet of our Paleolithic ancestors. In fact, the types of food rich in refined carbohydrates shown on the table above are very recent, typically dating back to less than a hundred years ago. That is, they are so recent that it is unlikely that any of us have genetic adaptations to those types of food.

Once one’s glucose metabolism is seriously impaired, which seems to be associated with consumption over many years of refined carbohydrates and sugars (as well as some genetic predisposition, which may have evolved among some of our ancestors), then even the foods with high glycemic index and low glycemic load (e.g., potato) will lead to highly elevated glucose levels if eaten in more than very small amounts.

Insulin resistant individuals should avoid even foods with high glycemic index and low glycemic load, as well as any food that significantly increases their blood glucose levels after a meal, because highly elevated glucose levels are toxic to various tissues in the body. The longer those highly elevated serum glucose levels are maintained, the more damage is done; e.g., 2 hours as opposed to 30 minutes at 180 mg/dl. One reason why they are toxic is because they lead to high levels of protein glycation; this is a process whereby sugar binds to protein and “warps” it, impairing its functions.

Generally speaking, the more glycation is going on in our body, the more accelerated is the aging process.


Loren Cordain, Michael R. Eades, Mary D. Eades (2003). Hyperinsulinemic diseases of civilization: More than just Syndrome X. Comparative Biochemistry and Physiology: Part A, 136, 95–112.


Anonymous said...


Good post. One thing I definitely agree with Doctor Davis on is the use of a glucose meter to characterize one's response to specific meals/food combinations. I also like the idea that fat and possibly protein can blunt the blood glucose response of potentially problematic foods. Again, the glucose meter should be able to detect this. I am going to start testing my blood sugar with all of the meals that I fix on a regular basis. It should be pretty interesting. Keep up the good work on the blog.


Ned Kock said...

Hi JC.

One thing to bear in mind is that, if you are on a low carb. diet, it is likely that you'll be more "sensitive" to carbs.

That is, your glucose response may be higher than what you would normally get if you were on the SAD.

ben nguyen said...

It seems higher carb sensitivity is a bad thing. Perhaps like those anti-bacterial soaps and lotions, if you constantly avoid all carbs, the body loses it's natural ability to defend against it!

Speaking of bacteria, I'm curious your take on fiber. For example, soluble fiber (inulin, etc) is said to have prebiotics that promotes low cholesterol and healthy large intestine bacteria. Similarly, do the bad carbs in insoluble fiber out weigh the goodness in preventing digestive cancers?

Assuming no wheat allergies, are the carbs and (inflammation causing) WGA lectins in whole wheat something to be avoided or reduced from the 30-35g that the rda recommends?

Ned Kock said...

Hi Ben.

For most people, the real problem with refined carbs and sugars is that they promote unnatural hormonal responses, which in turn lead to obesity.

Consumption of whole carb-rich foods, such as vegetables and fruits, is not generally a problem. These foods are rich in fiber; some more than others. They are also satiating.

The problem starts when we consume foods that were not meant to be consumed by any animal (e.g., seeds, unusually sweet compounds). These foods usually require heavy industrial processing, and lead to exaggerated hormonal (e.g., insulin, cortisol) responses.

Neonomide said...

Thanks for a great post!

Regarding carbs and obesity, how about the possible connection between leptin resistance and grain consumption ?

I believe that intestinal flora and of course intestinal permeability have a role as well. Certain sucky carbs may be simply a vehicle to greater problems when sugar/fructose Omega 3 deficiency, D3 deficiency and other toxic compounds and lifestyle factors damage the gut lining to allow certain lectins and anti-nutrients to mess up our first line defence against metabolic disease -inducing compounds.

Sorry if I derailed a bit. ^^

Ned Kock said...

Hi Neonomide.

I pretty much agree with all you said. If you take a look at this post, where I discuss my diet as I lost 60 lbs, you'll see that it is aimed in part at avoiding the problems you mentioned:

There is a hormone called adiponectin, which works closely with leptin, and seems to be equally important for health. And its blood concentration is 1,000 higher than that of leptin:

viagra online said...

This is incredible because I didn't know that glycemic is the responsible of the diabetics, that's interesting because my cousin has these problems maybe it could be the reason.m10m

Florent Berthet said...

Nice article, and thanks for the table, it's so hard to find glycemic load tables that use the same portions for each food (most sources use different portions, sometimes even mixing grams, cups, and sizes... How are we supposed to compare?).

I have a question: how much is too much in terms of glycemic load when it comes to glycation and AGEs? I guess it's not an on/off switch, but how much glycemic load would you say is the limit if we want to maximise longevity?

Also, in the case of the post strength training workout period, where muscle glycogen stores are partly depleted, can the glycemic load by higher without inducing glycation?

Anonymous said...

Here's the authoritative, searchable table for GI and GL table, and I like that is gives ranges, since not all products with the same name are the same: