The Big Problem With The Glycemic Index (GI)

glycemic-indexThe Glycemic Index, also referred to as the GI, measures sugar in the blood. The basic problem with the Glycemic Index is that it doesn’t measure all types of sugar, especially fructose, and this creates the false and persistent perception that some high sugar foods and drinks are less harmful than others when they’re not. All sugars, regardless of the type, have the same potential to cause food cravings, weight gain, metabolic dysfunction, insulin resistance and fatigue. There is no “official” tool for assessing the impact of all types of caloric sweeteners. All we have is the GI, which only measures glucose.

Firstly, a short lesson. The three most common types of sugars found in our food supply are glucose (sugar), fructose (fruit sugar) and maltose (malt sugar). They occur naturally in plant-based foods or drinks and in some dairy products. They can also be extracted and used as a sweetening agent by food manufacturers to make their packaged products taste better. Most of the sweet foods we eat are a combination of glucose and fructose. Table sugar, for example, is 50% glucose and 50% fructose. Even high fructose corn syrup is a blend. The HFCS-55 recipe has 45% glucose and 55% fructose.

As stated above, the GI only measures glucose. It doesn’t measure fructose or glucose-fructose blends. The reason fructose isn’t measured in blood sugar is because fructose and glucose metabolize differently. Glucose is digested and then shows up in blood for use as energy. Maltose breaks down into glucose and likewise shows up in the blood to be used as energy. Fructose, however, is not digested, is not broken down into glucose, and has no impact on blood sugar. Instead, it goes directly to the liver where it’s broken down into triglycerides to be used as fat. This is why the GI doesn’t notice or measure fructose. Even more importantly, the presence of fructose and the absence of glucose pulls the GI rating down. This then creates the misleading impression that fructose is more beneficial and less harmful than glucose.

The Glycemic Index uses a scale of 0 to 100 to identify how much sugar is in the blood after a food or drink is ingested. As a reference point, glucose has a GI of 100. Fructose has a GI of 23. Maltose has a GI of 105. Foods and drinks that have a GI value of 55 or above are considered high GI foods. Foods and drinks that have a GI value below 55 are considered low GI foods. Meat, fish, eggs, oils and high fat veggies do not have a GI value. For more specific information about the GI, visit, an international database developed and maintained by the University of Sydney, Australia.

The following table shows the most common caloric sweeteners and compares their calories, carbs, sugar grams, percent fructose and glycemic index. All measurements are for one tablespoon of the sweetener.

Type Sweetener Calories per Tablespoon Total Carbs (in grams) Total Sugars (in grams) Percent Fructose Glycemic Index
Table Sugar (sucrose) 45kcals 12 12 50% 65
HFCS 53 14 5 45%-55% 10-14
Dark Corn Syrup 57 16 16 0 90
Agave Syrup (nectar) 60 16 16 70%-90% 10-20
Brown Rice Syrup 75 18 11 0 98
Barley Malt Syrup 60 14 8 32-42
Coconut Syrup (nectar) 60 13 12 38%-48% 35
Maple Syrup 52 13 12 40% 54
Honey 64 17 7 48% 52-55
Molasses 58 15 11 13% 55

As you can see, it can be difficult and confusing to make a healthy food purchase decision based on the Glycemic Index and on information provided on the nutrition label. HFCS, for example, looks pretty good because it has relatively low calories, low sugar grams and a low glycemic index. But, of course, we all know that HFCS is not a healthy food choice and that fructose is strongly implicated as one of the biggest culprits in the obesity epidemic.

An easier and more fool proof way to make an assessment is to simply recognize that all caloric sweeteners, no matter what type, can be a weight and health hazard, and they all need to be managed with care. With this singular goal in mind, your new job is to identify the caloric sweetener that’s been added to the product and to make an educated guess about whether or not there’s enough of it to worry about.

The one and only place to figure this out is from the ingredients list, which is usually the smallest most hard-to-find information on the product package. The ingredients list is where the rubber meets the road because all ingredients must be listed, and they must be displayed in order of predominance. Whatever there’s most of has to be listed first. Whatever there’s the second most of has to be listed second. And so on. You get the idea.

If a caloric sweetener is listed as the first, second or third food ingredient in the product, there’s too much of it. This is your signal to look for another product. Smarter product choices exist, but you have to find them. If, however, the caloric sweetener is the fourth food ingredient or lower on the list, there’s not enough of it to worry about, and it’s a reasonable product choice.

This ingredient sorting exercise is called The Rule of Three, and it always works. Are the first three foods a caloric sweetener or not? That’s all you have to figure out. Keep in mind that food is not water. Food is not vitamins or minerals or flavorings. And food is not chemicals. Don’t include any of these substances in your three item food count. That’s really all there is to it. Now go do it.

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Posted in Sugar-Free Lifestyle