I’ve never met a glycemic index I liked

You’ve heard this before (though not from me): “For weight loss and health, choose foods with low glycemic index.”

Yes: And your sister is only half pregnant and your neighbor is a former murderer.

We don’t have to look far to find illogical ideas in nutrition—they are everywhere. And the concept of glycemic index is yet another. But if you understand why glycemic index is nonsense, you are empowered to obtain even greater control over weight and health.

Glycemic index, or GI, describes how high blood sugar climbs over 90 minutes after consuming a food compared to glucose.

The GI of three fried eggs? Zero: Blood sugar will barely budge at all. How about an avocado? Zero, too. This is true for meats, poultry, fish, oils and fats, nuts, seeds, mushrooms, and non-starchy vegetables. Eat any of these foods and blood sugar doesn’t budge, no glycation phenomena follow, no glucotoxicity, no lipotoxicity. (The exception: People who have damaged pancreatic beta cells that produce insulin and/or severe insulin sensitivity. In these situations, even proteins can raise blood sugar a little bit.)

There is nothing intrinsically wrong with the idea of measuring blood sugars after eating as glycemic index, nor of the related concept, glycemic load, a measure that also factors in the quantity of food. The problem is how the values for GI and GL are interpreted. The nutrition world breaks glycemic indexes down into:

High glycemic index: 70 or greater
Moderate glycemic index: 56-69
Low glycemic index: 55 or less

By this scheme, cornflakes, puffed rice, and pretzels have “high“ GIs, while whole grain bread, oatmeal, and rice have “low” GIs. A typical non-diabetic person consuming a serving of cornflakes, e.g., 1 cup cereal in ½ cup milk, will thereby experience a blood sugar in the neighborhood of 180 mg/dl—–very high and more than sufficient to set the process of glycation and glucotoxicity on fire, add to insulin resistance and adrenal disruption, cataract formation, destruction of cartilage, growth of visceral tummy fat, hypertension, heart disease, and neurological deterioration or dementia. In other words, that bowl of cornflakes was plain awful for health. (Blood sugars will vary, depending on body weight, degree of overweight, insulin sensitivity, time of day, and other factors, but this would be typical. Someone with pre-diabetes or diabetes will have a much higher blood sugar.)

How about a low-GI food, such as a bowl of oatmeal—yes: stone-ground, organic, no sugar added, 1 cup cooked, in ½ cup milk? A typical response: blood sugar 150-170 mg/dl—lower, yes, but still quite awful, triggering all the same undesirable phenomena triggered by the high-glycemic cornflakes. This is why I believe “low” GI is more accurately labeled “less-high” GI, not “low.” Recognize that any GI above single digits should be regarded as high because it’s not until you get to single digits or zero that blood sugars no longer range into destructive levels.

The concept of “glycemic load” tries to take this into account by factoring in portion size. Thus the GL of cornflakes is 23, while the GL of oatmeal is 13 and that of whole wheat bread is 10. GL is usually interpreted as:

High glycemic load: 20 or greater
Moderate glycemic load: 11-19
Low glycemic load: 10 or less

The GL for oatmeal is a misleading 9. Once again, this lulls you into thinking that foods like oatmeal or whole wheat bread don’t raise blood sugar—-but they do. They are not low GL; they have less high GL. And we haven’t even tackled the huge individual differences that exist between different people.

The value that truly appears to count and predict whether or not we will have a blood sugar rise? Grams of carbohydrate. Specifically, “net” grams of carbohydrate calculated by subtracting fiber:

“Net” carbohydrates = total carbohydrates – fiber

Net carbohydrates is a concept popularized by the late Dr. Robert Atkins, who recognized that fiber has no impact on blood sugar despite being lumped together with other carbohydrates. (Fiber is technically a carbohydrate, or polysaccharide, but humans lack the enzymes to digest most fibers into sugars.) In other words, there is really no need for manipulations such as glycemic index or glycemic load.

If you were to test blood sugars with a finger stick glucose meter 30-60 minutes after consuming a food, you would see that it takes most of us around 15 grams of “net” carbohydrates—regardless of GI or GL—before we begin to see a rise above the starting value. (This is especially true at the start of your Wheat Belly or Undoctored journey. As you get healthier—lose weight, regain insulin sensitivity, correct vitamin D and magnesium, cultivate bowel flora—your tolerance for net carbs may increase, something you can judge via your finger stick blood sugars pre- and post-meal. But the increase will be modest, certainly not something like 50 or 60 grams.) We check blood sugars at 30-60 minutes after consuming a food. The peak can actually vary in timing, depending on the mix of protein, fat, fiber, the amount of water or other liquids, pH of the food, and other factors. This is just an approximation that allows you to perform a single finger stick, rather than many to capture the peak. (What we do NOT do is check blood sugar two hours after consumption, as advised by most physicians interested in blood sugar control on diabetes medications.) Ideally, little to no rise in blood sugar is allowed, what I call “The No Change Rule.” In this way, you have turned off any excess levels of glycation and glucotoxicity, undo the effects of high insulin and insulin resistance, and allow fasting blood sugars to drift downward over time.

Less bad is not necessarily good. Feel free to count your carbs, but ignore the misleading concepts of glycemic index and glycemic load. Use those tables of glycemic index you might have to line your box of cat litter, but don’t use them to construct a healthy diet.

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Dr. William Davis

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