Constantly Craving
How the Glycemic Index of carbs affects your energy, appetite, and mood.
by Dan Duchaine
from MuscleMedia, August, 1997
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My wife used to routinely try to shame me into eating "cleaner." She'd say, "You eat such CRAP! Bodybuilders shouldn't crave angel food cake and Coca-Cola right before a workout. Honey, let me microwave you a potato and some chicken. That's real bodybuilder food."

I'd reply, "I can't eat potatoes. They make me sick... sleepy... nauseous. "

To which she'd retort, "You must tee the Hypochondriac Guru! A damn potato doesn't make you sick!"

Some carbohydrate foods just seem to make you feel tired: potatoes, bagels... Alpha Bits—but I expect that with all that sugar. Yes, there is such a thing as carbohydrate quality. Militant nutrition writers have lobbed anxiety-producing factoids at us like "Rice cakes are worse than sugar," but my amoral carte view is that there are no "bad" carbohydrates, just mistimed ones.

Glucose: The End of the Line

Eventually, all sugars and starches are reduced to the only sugar found in the blood: glucose. Although most of us eat hundreds, if not thousands, of calories of carbohydrates each day, healthy adults have only about 2 tablespoons, less than 100 calories, of glucose in their blood.

Both the quantity and the quality of the carbohydrates you eat determine how much insulin is secreted by your pancreas. Well timed carbohydrates ensure ideal energy levels, along with maximal glycogen storage in the muscles and liver. Mistimed carbohydrate choices can cause lethargy (from hypoglycemia) and increase bodyfat, as well as causing erratic mood swings. Chronic mistiming of some carbohydrate choices can raise blood triglycerides and "bad" LDL cholesterol, which both correlate with heart disease.

Previous Assumptions

Scientists have known for decades that some carbohydrates are digested more quickly than others. Until 1981, they assumed all sugars were the "fast" carbohydrates and all starches were the "slow" ones. Since sugars have lower molecular weights than starches, they assumed sugars must travel through the small intestine more rapidly, just as smaller amino acids and shorter chain triglycerides do.

The First Glycemic Index

Towards the end of the '70's, doctors specializing in diabetes discovered that many carbohydrates caused unexpected blood glucose levels. Some sugars were acting like "slow" carbohydrates, and many, many starches seemed to behave like simple sugars.

In 1981, Dr. David Jenkins of the University of Toronto (not Next Nutrition's David Jenkins, another one) tested the blood glucose levels of non-diabetic volunteers after they ate 62 common carbohydrate foods. He plotted the curve of the blood glucose levels, measured every 15 minutes during the first hour and every 30 minutes during the second. He used liquid glucose as a reference, with a score of 100.

Jenkins called his data the "glycemic index" (GI). Over the last 15 years, many other glycemic index experiments have been performed. In fact, the latest index has over 600 entries. Most scientists, doctors, and nutritionists agree with the glycemic index and have replaced their old idea of "simple" and "complex" carbohydrates with the new terms: low, moderate, or high GI.

Experimental GI ratings don't seem to differ greatly between normal and diabetic subjects nor men and women. The amount of water or alcohol consumed doesn't seem to affect the ratings either. There also seems to be no difference between naturally occurring sugars and processed ones.

Glucose or White Bread?

Since liquid glucose is not a common food, some scientists decided to use white bread as a reference instead. It's easy to convert. If you have only a glucose index, just multiply the GI by 1.43. Conversely, a white bread GI can be converted to the glucose GI by multiplying by .7.

Some foods, such as rice, potatoes, and pasta, have multiple GI's. Often this is caused by the plant species the starch comes from or the way the food is cooked. If these are not specified, researchers list a mean (average) of all the studies. For example, liquid glucose has been tested 8 times, with a low score of 85 and a high of 111. The average of the 8 studies is 97.

There is a consensus that a "low-GI" food is less than 55 on the glucose index or less than 79 on the white-bread scale. Picking carbohydrates of 55 or below will minimize conversion of blood glucose to triglycerides (ideally at or below 100 mg/dl in a fasted state) and keep "good" cholesterol (HDL) at 20 mg/dl or above.

GI Negotiations

Only single foods are listed in the glycemic index. However, I have found that the GI of a mixed-carbohydrate meal can be predicted with a simple formula:

Mixed GI = [(single food carb cal/total meal carb cal) x (single GI)] + [other carte source(s)]

This means that even though you might pick an unfavorably high GI food, like 150 calories of honey (GI 73), mixing it with 150 calories of skim milk (GI 32) and 150 calories of Special K cereal (GI 54) causes the GI of the mixed meal to be much lower.

By mixing low- and moderate-GI foods, one could eat some high-GI foods in a meal but still have an acceptably low total GI.

For example:

Honey: (150/450) x 73 GI = 24.3

Skim milk: (150/450) X 32 GI = 10.7

Special K: (150/450) X 54 GI = 18

Mixed GI: 24.3 + 10.7 + 18 = 53

Low-GI Benefits: Health and Performance

Even if you are not diabetic, there are some excellent reasons to use the glycemic index. As I have mentioned in previous articles, the currently fashionable high-carbohydrate diet can increase blood triglycerides, which can lead to elevated cholesterol and eventually heart disease. Low-GI foods, however, can help keep your energy levels stable.

In addition, noted researcher Dr. Ann de Wees Allen has shown that the natural release of growth hormone is suppressed by cartes with GI's over 50. Sports researchers have discovered certain foods are better for before and after training. And low-GI foods also alleviate hunger better than moderate- to high-GI foods.

Selecting the right carte at the right time will improve health and performance and prevent dramatic mood swings. Most savvy bodybuilders know this already. What you may not know is that many common-sense assumptions about GI's are simply incorrect.

Sugar Isn't All that Bad

Here are the GI's of the common simple sugars (using the glucose index):

Maltose (double glucose): 105

Glucose: 97

Sucrose (white table sugar): 65 (!)

Fructose: 23

Lactose (galactose): 46

Honey: 73

You can see that white table sugar has a moderate GI of only 65. As you will learn, many starches have a much higher GI than sucrose. Unlike starch, which uses only the alpha-amylase-glucosidase enzyme, many sugars are cleaved by other enzyme, which are less efficient. Also, both galactose and fructose are not immediately converted into glucose but have an intermediate conversion (needing additional enzymes) to glycogen in the liver. Scientists have long assumed that the highest GI foods were the mono- and di- saccharides. This is not correct. The highest GI carbohydrates are the glucose oligomers, which are starch chains between three and ten glucose molecules long, 9 such as commercially available maltodextrins derived from cornstarch. This is an embarrassing admission — I was involved in the introduction of maltodextrins into the sports supplement market in 1981, heralding them as the newest "complex carbohydrates."

Factors that Affect the Glycemic Index

GRAIN PROCESSING: The less processed a grain is, the smaller the surface area. Finely ground wheat flours might make attractive-looking, soft breads, but they are digested very quickly and thus have a higher GI.

GELATINIZATION: Inside a grain, starch molecules are grouped into dense structures called granules. Gelatinization occurs when water and heat cause the granule to swell, exposing more surface area. With enough water and heat, some starch molecules will break off, which is what happens when you heat water and wheat flour to make gravy.

STARCH COMPOSITION: There are two basic starch structures: amylose and amylopectin. Amylose is simply a straight string of glucose molecules. It looks like this:

0—0—0—0—0—0—0

Amylose is broken down slowly from the ends, like it is being eaten by Pac Man in slow motion. Amylose is also called "resistant starch" because only about 40% can be digested. Most starches have some amount of amylose in them. Uncooked cornstarch has about 70% amylose. Some types of rice have 28%; others have only 2%. The higher the amylose content, the lower the GI. Unlike the mock carbohydrates in the old starch blockers (or the prescription drug acarbose), amylose is not easily fermented. Starch blockers dump fermentable starch into the colon, causing, in polite medical language, "meteorism" (which is projectile vomiting from the opposite end).

Amylopectin, the more complex starch, has a structure that looks like this:

            0
            1
            0
            1
0—0—0—0—0—0—0—0—0
            1
            0
            1
            0

Every four or so glucose molecules, the chain branches. In this structure, our Pac Man-like enzymes can chomp away at the end of every glucose chain. There is more exposed area for the enzymes to attack, so amylopectins generally are digested faster and therefore have higher GI's.

There is one instance when this isn't true. Some new maltodextrins (usually fragmented amylose) are reduced amylopectins. A straight-chain maltodextrin has a high GI, but a branched-chain maltodextrin has a lower GI, which is why I like to use them in diet meal-replacement powders.

FIBER: The two broad categories of fiber are 1) soluble, such as oat, soy, fruit pectins, and gums (like guar) and 2) insoluble, such as the fiber in rice and wheat.

Soluble fiber is ideal for lowering the GI of other foods. As these fibers dissolve, they gel with the food in the stomach and slow gastric emptying. If you allow a serving of my ISO3 meal replacement to sit for a few minutes, the soluble soy fiber will change the liquid to a pudding-like consistency.

Insoluble fiber is only worthwhile when it acts as a barrier in an intact grain, so amylase cannot easily reach the starch. Adding insoluble fiber to ground grains, such as wheat flour, has no impact on the glycemic index. Commercial white and whole-wheat breads have similar GI's because the grinding of the grain has destroyed the barrier of insoluble fiber.

Intact rice fiber has no barrier action. So the GI's of most white, longgrain varieties are virtually identical to brown rice. However, adding a moderate amount of rice bran to a carbohydrate source will lower the GI because of the phytic acid content (see the section below on anti-nutrients).

SUGAR COMPOSITION: Fructose (found in fruits) and galactose don't cause much insulin secretion, which is why sucrose, which is half fructose, has a lower GI than many starches. Additionally, the enzymes that reduce disaccharides and convert them to glycogen reduce the level of glucose in the bloodstream.

Unripe fruits have lower GI's. For example, an unripe banana is almost 90% starch (some of which is resistant starch). The GI rises as the starches turn into sugars. Upon ripening, the starch content in a banana is less than ten percent.

FAT: Dietary fat slows gastric emptying. However, there are no studies proving any hard-and-fast rules for adjusting the GI of a meal downward with the addition of fat. One study that compared full-fat milk with skim milk showed a difference of only about two GI points. We can cautiously say that fat lowers the GI of a meal, but we don't know the details yet.

PROTEIN: Because solid proteins need to be liquefied in the stomach before moving into the small intestine, adding protein to a meal can lower the GI. One popular meal-replacement powder offsets its high-GI maltodextrins by including casein. Because whey protein remains liquid in the stomach, ISO3, my meal-replacement powder, contains both soluble fiber and monounsaturated fat to ensure a lower GI.

ACID CONTENT: High acid contents slow gastric emptying. Although pineapple juice is mostly sucrose (GI 65), its acid content lowers its GI to 46.

ANTI-NUTRIENTS: Anti-nutrients are compounds that interfere with amylase by binding with the minerals necessary for enzyme function, primarily calcium and potassium.

Not all anti-nutrients are benign. For example, the oxalic acid in yams, which causes them to have a lower GI than white potatoes, is poisonous in large amounts. Tannins, another common anti-nutrient (found in grapes and guarana and kola nut), are carcinogenic in extreme amounts.

Phytic acid is the best of the anti-nutrients. Not only does it significantly lower the glycemic rating of a carbohydrate (a small amount halved the GI of wheat flour), but it also acts as an antioxidant and guards against colon cancer. Currently I'm investigating the use of phytates in meal-replacement powders.

Interestingly, one of the protein anti-nutrients, lectin (found in soybeans and wheat germ), binds with sugars in the small intestine and imparts an insulin-like action.

Looking Over the Staples

Most pastas have lower GI's than wheat breads because they are made with semolina flour, which has a more compact starch granule. The physical size and shape of pasta can also influence gastric emptying: "angel hair" pastas have a slightly higher GI than fettucine.

Egg pasta is digested more slowly than pure wheat pasta, causing a lower GI. Whole-wheat pasta doesn't do much to slow digestion. Remember, the insoluble fiber in flour is no barrier to enzymes.

Pastas should be cooked as little as possible. Macaroni boiled for five minutes has a GI of 45. Macaroni and cheese, baked in the oven after the pasta has been cooked, has a GI of 64. The fat and protein in the cheese do not lower the GI as much as overcooking raises it.

Many people assume that pasta, because it is highly processed, must be "bad." However, of all the major starch sources, pasta has the lowest GI. Barry Sears doesn't like pasta simply because it is calorie dense, even though it is in the acceptable GI range for The Zone.

The fiber in brown rice is no great impediment to digestion, so picking a brown rice is not as important as identifying the amylose to amylopectin ratio. Long-grain rice has more amylose than other varieties. Both Basmati and Doongara have an average GI of just under 60.

Curiously, Uncle Ben's Converted Rice, a parboiled long-grain rice, has a GI of only 47. You would think that presoaking, steaming, and drying the rice would affect the GI negatively. "Instant" rice, which is slightly puffed during the drying process, has a GI of 80. The waxy, sticky rice commonly used in Chinese restaurants also has a very high GI.

The reason rice cakes are "worse than sugar," with a GI as high as 92, is that compression, high heat, and burst-steaming puffs the rice, causing a greater surface area.

This is the same process used to make most cold breakfast cereals. Since sucrose has a lower GI than highly processed grains, my beloved Alpha Bits have a lower GI than a low-sugar cereal like Rice Krispies (GI 95!).

Potatoes also have a wide range of GI's, from a low of 47 (raw potato), to a high of 84 (microwaved). Potato varieties have differing amounts of starch: red-skinned potatoes have the lowest GI's, while Russet and Idaho have the highest. As you can imagine, increasing the heat increases the GI, so boiling is best, baking is medium, and microwaving is the worst of all.

As breads go, the coarser the grain, the lower the GI. The only time this doesn't hold true is with pita bread, which has a GI of 57. Barry Sears was right to single out bagels, because they have a GI of 72, which would have been even higher without the extra protein in the gluten flour.

Legumes are an ideal low-GI food. They have a tough shell of soluble fiber. Their protein content further slows digestion. They have a spectrum of anti-nutrients and even contain indigestible sugars that bind with amylose. Every nutritionist highly recommends them on paper, but most people avoid them because of the excessive flatulence. However, many anti-nutrients which cause this problem are discarded with the cooking water.

Glycemic Index Discrepancies

The frustrating thing about the published research is that there are many conflicting findings. Although we've discussed the importance of consuming low GI foods, the most recent study showed no difference in athletic performance when athlete's consumed foods with varying GI's. A study involving pizza showed a similar GI to glucose, except that blood sugar levels were elevated for up to nine hours after the meal, compared to two hours for glucose. Maybe I should replace my pre-workout angel food cake with pizza!

New Research About the Post-Workout Meal

Researchers found that a powdered-malt extract, which was a mixture of glucose (10.8%), maltose (47.8%), glucose oligomers {41.2%), protein, and a spectrum of mineral salts caused a greater muscle glycogen I deposition than glucose or maltodextrin in animals.

Interestingly, the same muscle glycogen deposition occurred after adding roughly the same mineral salts to straight maltodextrin. Mineral supplementation is very important for enhancing glycogen deposition.

Since malt extract is readily available and cheap at beer-brewing stores, it may be used as an ideal carte-up source. If you choose to use straight maltodextrin (Parillo still produces one) instead of malt extract, the simple addition of a multimineral supplement will enhance the glycogen deposition.

To Sum It Up

What about my Coca-Cola and angel food cake? A combined GI of 65 isn't so swell. But I can get creative. If I eat an equal portion of low-fat, aspartame-sweetened yogurt (GI 14) with my angel food cake (GI 65), then my combined GI would be a very correct 40. And if I average my Coca-Cola (65) with my spaghetti (27) meal, I'll have a GI of 47.

Will it turn me into a Dorian Yates? As if. But my HDL cholesterol levels haven't been great lately, so just maybe I'll make my doctor happy, live longer, and "have my cake and..." Then again, I have a workout in three hours. I'd better call Domino's.