Take Very Good
Care of YouselvesDeuteronomy 4:15



BS'D

The Glycemic Index Continued
By David Mendosa

Are there Other Important Diet Considerations

The glycemic index should not be your only criterion when selecting what to eat. The total amount of carbohydrate, the amount and type of fat, and the fiber and salt content are also important dietary considerations. The glycemic index is most useful when deciding which high-carbohydrate foods to eat. But don't let the glycemic index lull you into eating more carbohydrates than your body can handle, particularly if you have diabetes. The number of grams of carbohydrate we consume is awfully important. Make sure you know the carbohydrate content of the foods you eat—study the nutritional information on the package

But first you need to decide the composition of your diet in terms of carbohydrate, fat, and protein. Almost all the experts agree that we should minimize our intake of saturated and trans fat and eat a lot more fiber than we do. Some other fats, particularly those from cold-water fish, seem to be beneficial. Beyond that, the battle rages between those who would have us eat more protein and those who say that carbohydrates should provide most of our calories. I'm no expert and am genuinely puzzled myself, although I have begun to cut back on my carbohydrates and eat more protein. Generally, foods high in fat and protein have lower glycemic indexes than foods high in carbohydrate. In a real sense, the glycemic index is not applicable to high-fat and/or high-protein foods

The problem is that even among the complex carbohydrates not all are created equal. Some break down quickly during digestion and can raise blood glucose to dangerous levels. These are the foods that have higher glycemic indexes. Other carbohydrates break down more slowly, releasing glucose gradually into our blood streams and are said to have lower glycemic indexes

Before the development of the glycemic index, scientists assumed that our bodies absorbed and digested simple sugars quickly, producing rapid increases in our blood glucose levels. This was the basis of the advice to avoid sugar, a proscription recently relaxed by the American Diabetes Association and others

Contrariwise, the experts thought that our bodies absorbed starches such as rice and potatoes slowly, causing only small rises in blood glucose. Clinical trials of the glycemic index have also proven that assumption to be false

Factors such as variety, cooking, and processing may effect a food's GI. Foods particularly sensitive to these factors include bananas, rice, and potatoes (for a fuller discussion of the GI of rice and potatoes see the section below). A 1992 study by Hermansen et al. reported that the GI for under-ripe bananas was 43 and that for over-ripe bananas was 74. In under-ripe bananas the starch constitutes 80-90 percent of the carbohydrate content, which as the banana ripens changes to free sugars. Particle size is also an important factor, according to a 1988 study by Heaton et al. The researchers found that the GI of wheat, maize, and oats increased from whole grains (lowest GI), cracked grains, coarse flour, to fine flour (highest GI)

In addition, the glucose response to a particular food may be somewhat individual. So it is probably a good idea to carefully watch your own blood glucose level after eating foods you have questions about and determine if they have high or low GI for you

So, the idea of glycemic index is a very useful one. But if you find a specific food produces an unexpected result, either high or low, take note of it and incorporate that into your meal planning

Also note that the numbers vary from study to study. This may be due to variations in the individuals in a particular study, other foods consumed at the same time, or different methods of preparation, since your body can absorb some foods better when they are well cooked

Most, but not all, of the foods tested are high in carbohydrates. Some may wonder at the gaps—why other high-carbohydrate low-calorie foods like celery (or tomatoes or similar foods) have never been tested. The problem is a technical one for the testers, because they would be so hard put to get anyone to volunteer to eat 50 grams of carbohydrate from celery—it's just too much celery to think about! Essentially, from a glycemic index standpoint, celery and foods like it can be considered as free foods. I now have a list of the common vegetables and fruits that are free foods on-line at http://www.mendosa.com/freefoods.htm

Mixed Meals

Some people wonder if the glycemic index can predict the effect of a mix meal containing foods with very different indexes. Studies have shown that it does that job very well, too

More than fifteen studies have looked at the glycemic index of mixed meals. Twelve of them showed an excellent correlation between what was expected and what was actually found

You can quite readily predict the glycemic index of a mixed meal. Simply multiply the percent of total carbohydrate of each of the foods by its glycemic index and add up the results to get the glycemic index of the meal as a whole. Professor Brand-Miller has an example on page 78 of her book The New Glucose Revolution. The report of a Joint FAO/WHO Expert Consultation "Carbohydrates in Human Nutrition" (cited in the Web bibliography below), has a comprehensive explanation and example in its section 6.3

The three studies that did not show the expected correlation came from a group of researchers who were not using standardized methodology for working out the glycemic index from the area under the curve. In addition, their meals were high in fat, which tends to reduce the impact of any one carbohydrate food

What About Protein and Fat

But what if the meal contains protein and fat too, as it usually does? How does that affect our mixed meal calculations

The conventional wisdom holds that between 50 to 60% of protein becomes glucose and enters the bloodstream about 3 to 4 hours after it's eaten. It's generally accepted that fat has little affect on blood glucose

In fact, recent studies indicate that neither protein nor fat have more than a minuscule affect on blood glucose. This seems to be true for people both with and without diabetes. The protein studies are particularly interesting

A 50-gram dose of protein (in the form of very lean beef) resulted in only about 2 grams of glucose being produced and released into circulation. Neither does adding protein to carbohydrate slow the absorption or peak of the glucose response

Fat delays the peak but not the total glucose response, according to these new studies. Therefore, it looks like you can simply ignore protein and fat in mixed meal calculations

"Of much greater concern is how protein and fat affect blood glucose levels in the long term," Jennie Brand-Miller of the University of Sydney writes me. "High fat and high protein diets have the distinct potential to induce insulin resistance, which would mean that any carbohydrate eaten would raise blood glucose and insulin levels to greater heights on a day to day basis. However, the type of fat may be important here. A recent study in Diabetologia showed that moderately high MUFA [monounsaturated fatty acids] diets improved insulin sensitivity, if the fat was less than a certain level (higher than 37% was associated with insulin resistance)

For fuller details you can check out the articles themselves

Franz, Marion J. "Protein Controversies in Diabetes." Diabetes Spectrum, Volume 13, Number 3, 2000, pages 132-141. The URL is
http://journal.diabetes.org/diabetesspectrum/00v13n3/pg132.htm
Gannon MC, Nuttall JA, Damberg G, Gupta V, Nuttall FQ. "Effect of Protein Ingestion on the Glucose Appearance Rate in People with Type 2 Diabetes" The Journal of Clinical Endocrinology & Metabolism, Volume 86, March 2001, pages 1040-1047. The URL is
http://jcem.endojournals.org/cgi/content/full/86/3/1040

Pizza

Many people have noticed that pizza seems to keep their blood glucose level high longer than just about any other food. While the reason remains a mystery, this folk wisdom now has scientific confirmation

Ahern et al. compared the effect on insulin-dependent patients of a pizza meal with a control meal that included high glycemic index foods. They found that although the initial glucose increase was similar for the two meals, the GI continued to rise and was significantly increased from four to nine hours after the pizza meal compared with the control meal.

Rice and Potatoes

Rice and potatoes are some of the foods most tested for their glycemic indexes. They are important both because most of us tend to eat a lot of rice and potatoes and because they can have a high glycemic index. Professor Brand-Miller reports the results of 49 studies of rice and 24 studies of potatoes. The results for rice ranged all the way from 54 to 132 and for potatoes from 67 to 158

What could possibly cause such tremendous variation? According to Professor Brand-Miller, for rice one of the most important considerations is the ratio of amylose to amylopectin. She says that "the only whole (intact) grain food with a high G.I. factor is low amylose rice, such as Calrose rice...However, some varieties of rice (Basmati, a long grain fragrant rice, and Doongara, a new Australian variety of rice [which is not available in the United States] have intermediate G.I. factors because they have a higher amylose content than normal rice

Wallace Yokoyama, a research chemist working for the U.S. Department of Agriculture in Albany, California, gave me a comprehensive explanation. There are, says this noted rice specialist, four types of rice: long-grain, medium-grain, short-grain, and sweet rice. Sweet rice is also known as sticky or waxy rice. It makes the best sauces and gravies, and is usually used in Asian restaurants. Sweet rice has no amylose, Yokoyama says. In other words, it is the rice that has the highest glycemic index. The three other types of rice have lower glycemic indexes

Of course, each of these three types of rice may be brown or white. Brown rice has a lower glycemic index than white rice, everything else being equal. Therefore brown long-grain rice—or if you can find it—brown Basmati rice—will probably have a lower glycemic index. White Basmati rice had a glycemic index of 83 in one study. Brown Basmati rice can be expected to have a somewhat lower index, but we don't know precisely what it is, because the studies haven't been done yet

In fact, however, Uncle Ben's Converted Rice is the lowest glycemic rice you can get. This is white rice. Jennie Brand-Miller has indicated to me that this company may use a secret process

Richard Jackson maintains in e-mail to me that my statement that there are three basic types of rice is "somewhat incorrect." He says that there is also a sweet rice used in oriental cooking. "It is not only very much stickier than standard Asian milled rice (such as Kokuro Rose Brand)," he writes, "but is perceptibly sweeter when eaten. It is typically fermented prior to cooking, whereas standard Japanese-style milled rice is not. I think if more research is done into this factor, the data may prove that the difference between sweet rice and regular Asian-style rice is different on the scale of caloric values as pertains to ingestion by diabetics

Among potatoes, new and some white potatoes have the lowest indexes. The reason that new potatoes have a lower GI is probably because most of the amylopectin is less branched—it is more like amylose at this immature stage

Fructose and High Fructose Corn Syrup

An addition to the published glycemic indexes is high fructose corn syrup, which is endemic in U.S. processed foods. Fructose is not the same as high fructose corn syrup, Professor Jennie Brand-Miller emphasized in a message to RonnieDbrg@aol.com, which he kindly faxed to me. "The former is pure fructose; the latter [high fructose corn syrup] is a mixture of fructose and glucose," she wrote. "In high fructose corn syrups, the fructose content is about 50 percent. Thus the GI of high fructose corn syrups is about the same as sucrose, i.e. 60-65 (if glucose = 100)." When white bread = 100, the GI of high fructose corn syrups is 85-92

Soy Milk

Soy milk has a low glycemic index of 43, according to e-mail from Professor Brand-Miller. The tested soy milk, she writes, has 4.5 grams of carbohydrates, 3.5 grams of fat, and 3.5 grams of protein per 100 ml. A low factor for soy milk isn't surprising, since soybeans have a GI of 25. But consumers in the United States—where many different brands and flavors are available—need to be aware that not all soy milks are created equal

I recently discovered that my blood glucose rose dramatically after a large cup of chai made with soy milk. That's when I paid attention for the first time to how many grams of carbohydrate that particular soy milk had. So then I looked through the nutrition information on the dozens of brands and flavors of soy milk (and rice milk and almond milk and oat milk, etc.) in our local natural foods store

I was amazed to find that the carbohydrate content of these beverages varied from 4 grams per 8 oz. to 36 grams. At least five brands have no more than 4 grams of carbohydrate per 8 oz. serving and are made from nothing but water and organic whole soybeans

WestSoy Organic Unsweetened Soymilk has 5 grams of carbohydrate per 8 oz. serving, of which 4 grams are fiber, which means it has only 1 gram of available carbohydrate per serving. The URL is http://www.westsoy.biz/products/organic.php

Pacific Original Non Dairy Beverage Unsweetened has 5 grams of carbohydrates, but 3 grams are fiber, which means it has only 2 grams of available carbohydrate per serving. The URL is http://www.pacificfoods.com

Soyfresh Unsweetened Soy Beverage also has only 2 grams of available carbohydrate per serving. The URL is http://www.soyfresh.com

Plain Yo Soy Traditional Soymilk from Wildwood Natural Foods is almost as low-carb. It has 3 grams of available carbohydrate. The URL is http://www.wildwoodnaturalfoods.com

Westbrae Natural Foods’ Westsoy 100% Organic Non Dairy Soy Beverage Unsweetened has 4 grams of available carbohydrate. The URL is http://www.novelco.com/westbrae/

You may also want to compare these numbers with cow's milk. It has 11 to 13 grams of carbohydrate per 8 oz, whether it is non-fat or full-fat. Also note that the carbohydrates in soy beverages have a lower GI than that of lactose, which is 65

Thanks

Thanks to Professor Jennie Brand-Miller for authorizing me to reproduce her glycemic index and glycemic load table. Thanks too to Tere Griffin who began the collection of information for what turned into this Web page and originally got me interested in this fascinating subject.

Too Complicated

There's nothing on my Web site that draws more visitors (and more e-mail questions) than my articles on the glycemic index. Ever since I reviewed the first Australian edition of The G.I. Factor by Jennie Brand-Miller and her associates at the University of Sydney for Diabetes Interview in August 1996 (online at http://www.mendosa.com/gifactor.htm), Jennie and I have maintained a close albeit long-distance relationship

I brought to her attention an article in The Washington Post that was critical of the glycemic index concept. That article, by Lawrence Lindner, executive editor of the Tufts University Health & Nutrition Letter, appeared as "What's Your Number, Sweetie? The Glycemic Index Is Science-Based—and Nearly Impossible to Follow," The Washington Post, May 1, 2001, is online at http://www.washingtonpost.com/wp-dyn/articles/A22159-2001Apr30.html

Jennie wrote a brilliant and short—and caustic rebuttal. Too trenchant for the Post, the newspaper has not yet published it and probably never will. It is, however, too good to go unread, and Jennie has authorized me to reproduce her letter here:

Imagine setting up a system of rating the energy content of foods and assigning a number—let's call them calories, the higher the number, the more energy they contain and the greater their likelihood of causing weight gain. We could use this system to guide food choices to lower energy intake.
Unfortunately, it's not that simple! The number would not tell us anything about the vitamin, mineral or fiber content. The numbers could be misleading—some highly nutritious foods like nuts and legumes have terribly high numbers (calories), while some nutritionally worthless foods have very low numbers (e.g. diet soda). What's more the numbers are not set in stone—they vary from time to time and just a slight change in the recipe would alter the number drastically. Let's dump the concept—it's way too difficult to follow

The worth of any food cannot be measured by a single number, but a single number can tell you a great deal about how the carbohydrate in that food affects blood glucose levels. High blood glucose levels are a risk factor for diabetes and cardiovascular disease. Dozens of studies have shown improvements in a variety of clinical outcomes with free-living subjects consuming self-selected low glycemic index diets

Like the calorie content of food, the glycemic index deserves some consideration. The foods that provide the most carbohydrate in the diet are the ones that need close attention (potatoes, breakfast cereals, breads, soft drinks), not carrots, honey or over-ripe bananas

For an extended bibliography please go to the website