Sunday, November 27, 2011

Exposing the Myth of Simple vs Complex Carbs

By Kenny Bellew
There is a myth involving simple versus complex carbohydrates that has flooded nearly every website that deals with the topic.

The myth goes like this: We need to avoid simple carbs because they digest more quickly than complex carbs, and this causes our blood sugar to spike.

What is usually meant by "simple carbs digest more quickly" is that simple carbs supposedly convert the carbohydrate's sugars into glucose more rapidly (which raises blood sugar) than most complex carbs. This is a myth based on a partial truth. Unfortunately, it leads to erroneous conclusions about simple carbs in general.

It's easy to demonize simple carbs because they are often referred to as the "sugars," but the truth is, all digestible carbohydrates are made of one or more sugar molecules. It all depends on how the carbohydrate is packaged. Is it a simple carbohydrate riding along in a strawberry that's packed with fiber, enzymes, vitamins and minerals, or is it a simple carb of sucrose sugar riding along in a piece of hard candy that is nutritionally empty? It’s all about the packaging, baby.

Another way this myth is spread is by saying fruit, a simple carbohydrate, more quickly converts to glucose. We will see that this is not true in almost all cases.

After reading lots of websites and watching numerous YouTube videos on simple vs complex carb, I've discovered that, as of mid 2011, people commonly confuse the definition of "simple carbohydrates" with the idea of "empty calories," or they think simple carbs rush into our bloodstream faster than complex, and they think that is why they are called “simple.”

To understand why this is untrue, let’s review a few details about carbohydrates and their role in our diet.

On the molecular level, carbohydrates are made up of one or more sugars (sugar molecules that bond together). If the carbohydrate is made of less than three sugars, it is classified as a simple carbohydrate. Examples of simple carbs include glucose, which our bodies use for fuel, sucrose, or common table sugar, fructose, found in fruit, and lactose, found in milk.

Carbohydrates that are composed of three or more sugars are starches, or more commonly referred to as complex carbohydrates.

Examples of complex carbohydrates include breads, grains, pasta, rice, corn, legumes, potatoes, vegetables like kale and fiber (soluble and insoluble).

I should pause to say that most food items, both processed and natural, can be a mixture of simple and complex carbohydrates. When food items are classified as simple or complex, it is usually because the ratio of these carbohydrates within the food item.

Carbohydrates fall into three broad classifications: sugars, starches and fiber.

Sugars are the simple carbs (glucose, fructose, lactose, etc). Starches are the complex carbs (except fiber). The third carbohydrate is fiber. Plants contain both soluble and insoluble fiber, both, of which, are non-starch polysaccharides, meaning fiber is a complex carb but not a starch.

All non-fiber carbohydrates are made of sugar molecules. It's the number of sugars that determine whether or not it's a simple or a complex carbohydrate. The number of molecules has nothing to do with nutrition levels that get packaged along with the carbohydrates.

When we eat carbohydrates, our bodies convert most of the carbohydrates to glucose, which enters our blood stream and raises our blood glucose levels or, in other words, our blood sugar levels. Our pancreas secretes insulin to shuffle the blood glucose into our cells, and some of it goes to our liver to be stored as glycogen.

The logic of the simple-versus-complex carb myth proceeds like this-- Because complex carbs are composed of a greater number of sugar molecule chains, it takes the body longer to break apart and convert the various sugars into glucose. Because it takes longer, we do not get a sudden rush of glucose in our blood, which causes the pancreas to release insulin for the purpose of forcing the glucose into our cells.

It sounds logical that it would take longer to break down the molecular chain to convert complex carbs to glucose than it takes to convert simple carbs with fewer sugars, but, in fact, IT DOES NOT! Yet this myth is repeated over and over on many respected websites and by many respected nutritionists. It's a myth long ago disproved. The exception would be to consume straight glucose, but who does that?

A glance at the glycemic index should be enough to validate this as a myth. The glycemic index measures food items by how quickly they raise blood sugar levels after consumption. The glycemic load compares food items by volume and their effect on blood sugar. Observe the glycemic index of fruits, which contain simple sugars, largely fructose but also sucrose and glucose. Nearly all fruits, with very few exceptions, have a lower glycemic load than most complex carbohydrates, certainly all of the white ones (white bread, white rice, noodles, and potatoes).

The glycemic index has been in common use since the early 80's; yet, the myth that all simple carbohydrates are "bad carbs" persists.

This myth that simple sugars caused blood sugar spikes faster than most complex carbs was dispelled in the 80's by a Canadian research team led by nutrition scientist David Jenkins, MD. It was Dr. Jenkins who pioneered the glycemic index.

The following is a quote from Dr. Jenkins:

"Originally, sugars — referred to by nutritionists as simple sugars — were contrasted with starches — referred to as complex carbohydrates. We assumed that the simple sugars were always more rapidly absorbed than complex carbs, and so caused a sharper, stronger rise in the blood glucose level. Their consumption was linked to obesity and diabetes.

But with time, it became apparent that the glycemic index of white sugar (sucrose) and white bread weren’t so dissimilar, and that some sugars such as fructose were even more slowly absorbed than the glucose from many starches. Furthermore, it turned out that fructose is poorly converted to glucose and so raises the blood glucose far less than once feared."

Fructose and the metabolic syndrome
by David Jenkins, MD
Vol.17, No.06, June 2009

One reason that fruit does not raise blood glucose levels as quickly as would be expected (considering the amount of sugar in a fruit) is that fructose cannot be converted to glucose in the same way that the body converts complex carbohydrates to glucose. In fact, fructose is not even digested. It just passes into the blood stream. However, being in the blood stream is not the same as being blood glucose, nor is it the same thing as being easily available as a fuel source.

The complex carbohydrates are broken down by enzymes into simpler sugar molecules. For example, the lactose in milk is a disaccharide (meaning a bond of two types of sugar molecules). It is a bond of the two monosaccharides: galactose and glucose. Our bodies use the enzyme lactase to break apart lactose into its simpler forms. You’ll probably recall that some people lack, or have little of, the enzyme lactase, which makes them "lactose intolerant." We need enzymes to digest our food.

If digestion works properly, the chains of glucose molecules are broken off from the complex carbohydrate and made available as blood sugar. However, when we ingest a monosaccharide like fructose in fruit, our bodies cannot break off glucose chains, because it doesn't have any. So, it's not even possible to "break down" fructose to glucose.

In order to convert fructose into glucose, the fructose is converted to a pyruvate through a process of chemical rearrangement called glycolysis. Once fructose becomes pyruvate, it doesn't necessarily mean that it will automatically be converted to glucose. The body can use pyruvate for a variety of things, but it only converts pyruvate to glucose if the body's blood glucose levels are low, and it does not have a better way to get glucose.

This is why Dr. David Jenkins, of the glycemic index, said that fructose was actually bad at converting to glucose.

So, why am I so worked up? The problem is that simple carb myths form the basis for a lot of bad recommendations by supposedly reputable experts. For example, I often see recommendations to avoid fruit because it causes spikes in blood glucose levels. This is false and potentially damaging to the health of the person who avoids the benefit of fruit. Examine a fruit's glycemic load before deciding it will spike blood glucose levels.

Getting it wrong:

I want to show you who is getting it right and who is getting it wrong. The following is just a sampling of the majority of health websites and YouTube videos.

I challenge you to do a Google search for “simple vs complex carbs” or “good vs bad carbs” and see how many websites still repeat this myth that simple carbs are digested more quickly than complex carbs or that simple carbs are the "bad" carbs. You will see it over and over almost without exception (as of mid 2011).

MedlinePlus: Trusted Health Information for You

Carbohydrates are classified as simple or complex. The classification depends on the chemical structure of the food, and how quickly the sugar is digested and absorbed.

This is a government website (apparently), and says that carbs are classified as "simple" by "how quickly the sugar is digested and absorbed."

That's incorrect. They got the first part correct, and then they added inaccurate "popular belief." It is true that a carb is classified as simple if it has fewer than three linked sugar moleucules, namely the common monosaccharides (glucose, galactose and fructose), and the disaccharides (sucrose and lactose). However, the number of linked sugar molecules has nothing to do with how fast the carbohydrate is converted to glucose in the body, especially if the simple carb is a non-glucose monosaccharide. As I have shown, the simple carb fructose cannot be broken down to glucose in the same manner as complex carbs.

The Oprah Show Website
Their website warns of the dangers of simple carbs by saying, "Regularly overindulging in simple, high-GI carbs...can be dangerous."
In the above, “GI” means “glycemic index.”
Again, the myth that simple carbs cause spikes in blood sugar levels. In reality, none of the simple carbs except straight glucose have a higher glycemic index or glycemic load than a slice of white bread, which is a complex carb- not even a tablespoon-full of raw granulated sugar (sucrose) has a higher GI than the complex carbs of a slice of white bread. It may be true that over-indulging in sugar can cause health problems, but the Oprah website is making a point related to the glycemic index and getting it wrong. Nearly everything that has a high GI is either a complex carb, a processed food or both.

I think the confusion comes from the use of sugars in things that are empty calories (nutrient bare). However, this is confusing the packaging with the contents. Fructose, a simple carb in fruit, comes packaged nutrient and fiber rich.

The View from the Bay show
Nutrition counselor and founder of Jamie Living proclaims, "The simple carbohydrates kind of shoot up your blood sugar level and then drop you down quick."

Here, a proclaimed expert, who was called specifically to talk about carbohydrates, does not understand the basic principle. It is the starches of complex carbs that are more likely to drive up blood sugar levels than the simple carbs like fruit or even table sugar. If it's blood sugar you're concerned about, demonize the white starches like white rice, pasta and white bread with equal or greater gusto. Compare the simple carbs of an apple to those of a bagel and see which affect blood sugar levels. Simple carbs win again.

Don't get me wrong. I'm not promoting empty calories like sugar candy, which are simple carbs. I'm pointing out the misconception that ALL simple carbs in ALL forms are the icon of fast-rising blood sugar, or that they are the "bad carbs." It’s an over-simplification that leads to misinformation.

Diabetes Action: Research and Education Foundation
In this example, an expert is dispensing health advice to a diabetic who wants to know if he or she should avoid fruit and fruit juices. The expert tells the person that fruit and fruit juice are "quick convertors to glucose."

There's no explanation about what type of fruit juice, whether it has added sweeteners, so I can't comment on that, but the expert is just plain wrong about fruit. We've seen that fructose actually is bad at converting to glucose. It is true that fruit also contains a ratio of sucrose and glucose, but examine the glycemic index, and you'll find that nearly all fruit has a low glycemic load. Compared to other carbohydrates that diabetics should concern themselves with, fructose in fruit is not a "quick converter to glucose." However, I'm not a diabetic expert. If you're diabetic, test your glucose levels after eating fruit and see.

NutritionMD, a health and nutrition website operated by the Physicians Committee for Responsible Medicine.

Sometimes it's the half truths that perpetuate and sustain myths the most. In the quote below, this medical website wants to warn us about the evils of nutritionally empty calories like sugar, jellies, candy and soft drinks. They do so by trying to demonize simple carbs. It seems that because table sugar is a simple carb, and people abuse it, people think all simple carbs are empty and evil regardless of how they come packaged. They should be condemning nutritionally empty calories, not simple carbohydrates. Here's the quote:

"All simple carbohydrates are made of just one or two sugar molecules. They are the quickest source of energy, as they are very rapidly digested. Unfortunately, most foods high in simple carbohydrates contain few nutrients other than calories. They also lack fiber and pass into the bloodstream rather quickly. Therefore, it is best to limit your intake of simple carbohydrates."

In the above, simple carbs are not the quickest source of energy. Processed starches, which are complex carbs, are much quicker. And to say that most simple carbs contain few nutrients and lack fiber points out that this committee of physicians are not even aware that fruits are largely simple carbs and fiber.

I could go on and on. Even though the Glycemic Index has been out for 30 years, the myth that all simple carbs raise blood sugar more quickly than all complex carbs is so prevalent on the internet and in the thinking of health professional that it seems it may never go away.

Let's look at a few websites that are getting it right.

Getting it right:
WebMD specifically points out that fruit carbohydrates are among those that are absorbed slowly into our bodies.

"These carbs that get absorbed slowly into our systems, avoiding spikes in blood sugar levels. Examples: whole grains, vegetables, fruits, and beans."

Harvard Health Publications: Harvard Medical School

This Harvard online publication, Carbohydrates and Health: Not that Simple…or that Complex, hits the nail on the head.

No one had actually compared the effects of various carbohydrate-rich foods until a Canadian team started to do this systematically in the 1980s. The results shattered long-held assumptions that the body took longer to convert complex carbohydrates into blood sugar.

Nutrition scientist David Jenkins compared the blood sugar responses of foods and compared them to the response to an equal amount of glucose, a simple sugar. To make things simple, they gave glucose a score of 100. Foods that increased blood sugar more than glucose get scores on this glycemic index of greater than 100. Those with smaller effects got scores under 100.

Pure fructose, among the simplest of simple carbohydrates, barely registered on the scale, with a glycemic index value of 20 (meaning its impact was 20% of glucose). But cornflakes, carrots, and potatoes—complex carbohydrates by anyone's reckoning—raised blood sugar levels almost as much as glucose.

A later modification called the glycemic load measures how eating a normal portion of a particular food affects blood sugar. Watermelon, for example, has a fairly high glycemic index value of 72. But there's very little carbohydrate in a serving of watermelon, so its glycemic load is low.


I hope that people will read this and take away a couple of points. First, simple carbs do not equal "the bad carbs," let's give that moniker to the white starches like white bread, pasta and white rice.

Second, simple carbs usually do not raise blood sugar faster than complex carb, or, more specifically, faster than the said bad carbs.

Third, most fruit is not good at raising blood sugar. Don't give freshly squeezed apple juice to someone suffering from low blood sugar. Instead, give them a piece of bagel or white bread.


  1. A great article. I have experienced the truth of what is affirmed here first hand. For five years, after finding my sugar levels were too high, I went on a raw fruit diet. This brought my sugar levels down. Even a few doctors were skeptical about whether I really had been eating fruit. I knew the truth. Eventually I did find a few MDs that had studied nutrition and knew that fruit does not spike our sugar levels.

  2. Great information. I especially like the section on fructose. I’ve been back and forth on this subject for a few years trying to decipher whether it is bad or not. The related articles via the web sway greatly both ways in regards to the danger or fructose. Thanks for including the sites—I’ll check them out.