Examining The Rights and Wrongs of Carbohydrates with the Glycem

Remember when carbohydrates had the favorable reputation of being the most important macronutrient? Years ago, all the experts agreed - carbohydrates, being the most important source of energy, were the food of choice for athletes or anyone seeking a boost in vigor and pep. Now it’s just the opposite.

By Vincent Chen, N.D.   Talk to the Author.

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Examining The Rights and Wrongs of Carbohydrates with the Glycem Remember when carbohydrates had the favorable reputation of being the most important macronutrient? Years ago, all the experts agreed - carbohydrates, being the most important source of energy, were the food of choice for athletes or anyone seeking a boost in vigor and pep. Now it’s just the opposite. The trend of late is to avoid carbohydrates, as many popular diets now recommend, since they’re evidently perceived as the culprit behind fat gains and health problems, not to mention the national debt and the recent power outages.

As it turns out, both cases are right and wrong. How is that possible? Simple. Carbohydrates are an extremely important energy source, so the experts of yesteryear have a point. But the wrong types of carbohydrates can lead to fat gains and other disease-producing issues. We’ll chalk that up to the new school. These elementary statements lead to one simple conclusion. Namely, it all comes down to the type of carbohydrate.

The attention paid to the type of carbohydrate has given rise to an effective classification system - the glycemic index. This is a measure of how quickly a carbohydrate is broken down and subsequently released into the bloodstream. Amazingly, this has quite a dramatic effect on how the body handles not only the recently ingested carbohydrate, but how it handles fat, protein and a litany of other chemicals swirling around your bloodstream.

All carbohydrates are eventually broken down into glucose and released into the bloodstream. But it’s the amount and speed of glucose entering the blood that determines the corresponding release of insulin from the pancreas. The more carbohydrate you ingest, and the faster it gets in the blood, the larger the corresponding surge of insulin, which stimulates the transport of glucose, proteins and fats out of the blood and into cells.

What does this do? Well, for starters, it zaps your energy since the glucose is no longer in your blood. But it also pushes fat into cells, and unless you’re trying out for the lead role in an opera, you don’t want that either. Now, pushing protein into cells is not such a bad thing, so insulin can’t exactly be considered evil. But you’d rather have that response after training so the protein can aid recovery and muscle building. So, a fast acting carbohydrate (one with a high glycemic index ranking) taken after training is a good thing, but that’s about the only time it’s helpful.

Prior to exercise in particular, ingesting a fast acting carbohydrate only diminishes the energy potential for your impending workout. That’s where insulin over does it by pushing everything out of the bloodstream, leaving you about as energetic as a granite sculpture. Worse yet, the resulting increase in fat storage presents a profound disadvantage for anyone seeking weight loss. Ideally then, to provide sufficient energy for training (and possibly the optimal environment for physique enhancement), the glucose response should be gradual and maintained. This underscores the importance of ingesting carbohydrates that are slow to reach the bloodstream (ones with low glycemic index rankings). Not only does this ensure adequate energy for sustained exercise bouts, it slows the corresponding insulin response, which decreases the odds that you‘ll become a big tub of fatty goo.

Traditionally, classifying carbohydrates into “simple” and “complex” categories was the norm in educating athletes and laypersons about the purported benefits and pitfalls of this macronutrient. According to accepted sports nutrition dogma, simple carbohydrates, such as those found in fruits and high sugar foods, reportedly triggered a rapid and large rise in blood glucose levels, followed by a rapid and often greater fall. In contrast, complex carbohydrates, such as pasta and starchy vegetables, were labeled as nutrient-rich and seemingly induced a more sustained blood glucose response.

Unfortunately, this system does not accurately account for the delicate diversity of carbohydrate-rich foods, nor does it provide meaningful information to direct food selection. In fact, the preceding characterizations are largely inaccurate and oversimplified. For example, although fruits contain primarily simple carbohydrates, there exists considerable disparity in the corresponding glucose responses following their ingestion. Interestingly, many kinds of fruit provide an ideal glucose response, while many forms of pasta (a so-called complex carbohydrate) spawn an unfavorably rapid one. Confusing matters is the fact that many foods contain both simple and complex carbohydrates. Moreover, numerous foods that contain simple sugars are often incorrectly labeled as unhealthy, while many complex carbohydrates are in fact nutrient-poor.

That’s where the glycemic index (GI) comes into play. As stated earlier, the GI is a ranking of foods based on their actual blood glucose response following consumption. Therefore, the GI reflects the rate of digestion and absorption of carbohydrate-rich food, and by utilizing the GI, one can reliably form appropriate meal choices to potentially promote enhanced fitness.

The following table summarizes the GI of common foods and partitions them into high, moderate and low categories. The number assigned to each food represents the speed at which the food is digested and subsequently absorbed, with higher numbers reflecting a faster introduction of glucose into the bloodstream. You should choose carbohydrates towards the medium to low end of the spectrum for the most part, with the exception of immediately post-workout, when high-glycemic carbs are recommended. Before a workout, you should definitely ingest low glycemic carbs (apples, barley, and lentils) 60-90 minutes before training. This will not only provide a nice sustained release of energy, it will promote increased fat burning during your workout. And to think there’s people out there that say all carbs are bad?

The Glycemic Index of Common Foods

High		Moderate		Low
Food	Glycemic Index	Food	Glycemic Index	Food	Glycemic Index
Glucose	137	Muffins	88	Grain bread	69
Instant Rice	128	Ice Cream	87	Grapefruit juice	69
Crispix cereal	124	Cheese Pizza	86	Green peas	68
Baked Potato	121	White Rice	83	Grapes	66
Cornflakes cereal	119	Popcorn	79	Linguine	65
Rice Krispies cereal	117	Oatmeal Cookies	79	Macaroni	64
Pretzels	116	Brown Rice	79	Orange	63
Total cereal	109	Spaghetti, durum	78	Peach	60
Donut	108	Sweet corn	78	All-Bran cereal	60
Watermelon	103	Oat Bran	78	Spaghetti, white	59
Bagel	103	Sweet Potato	77	Apple juice	58
Cream of Wheat	100	Banana	77	Apple	54
Grapenuts cereal	96	Special K cereal	77	Vermicelli	50
Nutri-grain bar	94	Orange juice	74	Barley	49
Macaroni and Cheese	92	Cheese tortellini	71	Fettucine	46
Sucrose	92	Pumpernickel	71	Lentils	41
Raisins	91	Chocolate	70	Fructose	32

Note: Index based on reference to white bread (GI = 100). This table was formulated from information gained from the following study: Foster-Powell K, Brand Miller J. International tables of glycemic index. Am J Clin Nutr. 1995;62(Suppl.):871S-893S.

The table also illustrates the obvious unpredictability of making nutritional choices based on traditional belief and/or subjective appeal. For instance, fructose possesses a surprisingly low index, while apparent “powerhouse” energy sources such as potatoes and bagels rank rather high. Since the GI also, albeit indirectly, provides an indication of the ensuing insulin response of food consumption, high-GI foods eaten in isolation are not recommended prior to training. But you knew that already. You also know that they’re disadvantageous for anyone seeking weight and body fat losses. Remember, you only need them after a workout, when they can help you recover and push needed protein into muscle cells.

Since foods are usually eaten in combinations, it is important to note that the glycemic index of a meal is usually lower than the glycemic index of the highest constituent. For instance, if equal calories of a bagel and an apple are combined, the glycemic index of that meal becomes a more acceptable 79. Protein also helps matters, such that they efficiently decrease the total glycemic index by slowing the absorption rate of carbohydrates and thus slows the insulin response. Since those seeking weight loss should strive for a stunted insulin release, this emphasizes the importance of combining protein and carbohydrates in each meal.

So that’s your glycemic index primer. You see? Carbohydrates don’t have to be avoided completely, you just need to eat the right ones at the right times. In doing so, you might just lose some fat, gain some muscle and improve your health. For more on these topics, check some of the feature articles around the website. Good luck.

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