NUTRITION > Glycemic impact of foods

Carbohydrates and Man


When discussing nutrition, there are some arguments that surprisingly never get mentioned, as if for some strange reason, we purposely try to avoid having to face some important truths. Perhaps the most important argument is the glycemic index (GI) of foods. The GI is a measure of the sudden variations in blood sugar levels due to the assimilation of the nutrients contained in a particular food. This issue is so fundamental that it should be the main reason driving us to stay in shape, to maintain a healthy body weight and thus to reach a state of well-being both on a physical and on a mental level. I'm not exaggerating. The impact that our diets have on our health and our mood is directly related to its glycemic index and we can immediately see its effect take place.

Before diving into the following article, I'd like to take a moment to explain the “natural” relationship between carbohydrate sources and man on an evolutionary scale. Without this information, the concept of glycemic index and glycemic load can seem like abstract ideas whose application is limited only to science. However once we fully understand the reasoning behind it, it is easier to apply its rules and to incorporate it into our daily lives.

As I have mentioned in the articles “Why Do We Gain Weight?” and “Empty Calories”, weight loss and its impact on our health is not so much a result of the amount of calories in our diet as it is the source of those calories.
When I spoke of different metabolic destinations for various nutrients, I meant that the calories in foods can have different biological effects regardless of the amount of those calories. For example, proteins can transform into structural material instead of becoming energetic substrate which means that its function is not measured in calories and that it is measured using different parameters than those of carbohydrates. Take for example a growing child or a training athlete. Even fats, commonly denounced in popular diets, can play an important role in any weight-loss program, as already explained in the article “The Omega 3 World”.

The difference between different types of carbohydrates

Different types of carbohydrates exist and each require a different process for digestion and assimilation. What groups them all together in the same family is their basic chemical formula: carbon, hydrogen and oxygen in the ratio C6H12O6 (or simply CH2O). Their molecular structure however changes depending on whether the compound is glucose, fructose or galactose. Furthermore, this changes also if each basic molecule is isolated (becoming monosaccharides) or more complex (disaccharides and polysaccharides such as malts and starches).

The Role of Carbohydrates in the Evolution of Mankind

Let's now take a step back and ask why are carbohydrates important and why are they a part of our diet? The answer to this is that our organism has learned to use mainly glucose as a source of energy. It has learned to extract glucose from those foods that contain it in a complex form, such as the starches in grains, through the breakdown of the bonds between one molecule and another. Furthermore, it has learned to convert different carbohydrates and even different macronutrients (proteins) in glucose through the process that is known as gluconeogenesis. Thus, carbohydrates are necessary. However, consider that for the most part of the history of mankind, carbohydrates were available for humans (gatherers) only in raw, whole, unelaborate forms. Thus our organisms are actually designed to receive carbohydrates from certain sources instead of others. One of the main evidences of this truth is how different glycemic indexes of different foods affect our health.

For most of mankind's past, humans gathered fruits and vegetables and ate them in their natural form, often without cooking or modifying them in other ways. These foods had a low calorie content, a high concentration of micronutrients and a low glycemic index. The glycemia remained fairly constant and evenly distributed over time. When cooked, some of these same foods lose much of their nutritional components (vitamins and dietary minerals) and their GI increases since the heat makes carbohydrates faster for the body to assimilate. These foods are however compatible with man's diet as they have been woven into the evolution of our species over time.

In Harmony with What the Season Has to Offer

Man has always gathered what he could find and even after agriculture was first developed, seasonal foods were what he cultivated. A seasonal fruit has very different nutritional characteristics from a fruit that has been cultivated off-season with artificial methods. It is logical to think that man is in harmony with nature and that our bodies are designed to consume the types of vegetables typical to a geographic location during a specific time of year, for the simple reason that this is the context in which man has evolved. It is for this reason that on the homepage of our site, you will find a list of the fruits and vegetables typical for the current month, to help you in creating your menus day by day.

The Main Sources of Carbohydrates Today

If you take a careful look at the kinds of foods that we typically consume in today's modern age, you will notice that a great part of these foods have only recently become part of man's diet (we say “recently” considering the long history of mankind) and have completely different characteristics comparing with the foods we spoke of above: high calorie content, medium to low concentration of nutrients and a high GI. I am referring to bleached flours and refined sugar. Let's consider a first factor: grains and cereals, like legumes, contain what is called antinutrients (phytic acids for example) which are not only incompatible with our diets but can actually be toxic for humans. These antinutrients can be reduced or eliminated by simply cooking the food or through other techniques such as sprouting and fermentation. These foods were not part of man's diet for the most part of his evolution. In ancient times, human beings did not have the means to transform their foods in sophisticated ways. Think, if you found an apple tree, you could pick an apple, clean it roughly and bite into it. You might find it difficult to peel its skin without a knife, but you could eat it all the same. Likewise, if you found some lettuce or berries.
But if instead you found yourself in a field of wheat, a rice paddy or a corn field…without modern man's tools and know-how, it wouldn't be so easy to come up with something edible. And even with simple tools it would be very difficult to obtain the kind of refined end-products that we find on the market today. Either way, whatever you obtain would have to be cooked since man cannot feed on raw grains.

Foods With a Low Calorie Content, High Concentration of Nutrients and Low Glycemic Index Vs. Foods with a High Calorie Content, Medium-Low Concentration of Nutrients and High Glycemic Index

It is common knowledge that our bodies need essential micronutrients such as vitamins, dietary minerals, polyphenols, trace minerals, etc. The lower a food's calorie content, the higher the concentration of these micronutrients. Keep in mind that our species has evolved thanks to the foods that were available. Therefore, fruits and vegetables are the carbohydrate sources that are most suitable for man since man's genetics have adapted to these during the course of evolution.
Back to the glycemic index. Experimental data reveals that the lower the calorie content of a food, the lower the GI. Thus, our bodies find it much easier to handle whole foods, raw foods, foods that have a low caloric concentration, foods that are usually of intense colors and flavors. Refined and processed foods on the other hand, are of high calorie content, normally have a neutral flavor (in fact we usually use these foods to accompany other foods that have stronger flavors, i.e. pasta, breads), are not edible if not cooked, and have been made available only recently because of their complex processing. These foods create problems for our metabolism and prevent us from handling glycemia properly, whose constance is fundamental for the nervous system to function correctly.

Low Carb Diets and the Paleo Diet

With this information on hand, many diets have been developed that suggest the consumption of low quantities of carbohydrates and high quantities of proteins and fats. There are also diets that are modeled after mankind's evolution, such as the paleo diet. Some of these ketogenic diets can become drastic, they are based on the consumption of an extremely low amount of carbohydrates which leads to a metabolism based on the energy produced by the partial breakdown of fatty acids which generates by-products called ketone bodies.

Low carb diets may or may not be the proper way to nurture our bodies (there are numerous debates over this issue but we will not focus on that in the current article) but they have certainly brought attention to the central role carbohydrates assume in our modern diets. The integrity of our food pyramid, the main pillar in our mass education on health, has now been put under debate in light of the increase (despite improvements in science and medicine) of those diseases thought to be related to the wealth and well-being of modern societies -- diabetes, hypertension, obesity, etc. -- pathologies directly linked to an incorrect choice of the quantity and quality of carbohydrates.

Carbohydrates and Satiety

- Calorie Content and Volume
Low calorie content means that to reach a certain number of (potential) calories you need a large quantity of a certain food. High calorie content means the opposite. For example, it can prove difficult to eat the amount of vegetables that would contain the same amount of carbohydrates as a plate of pasta or three or four slices of white bread, because of the large quantity one would have to ingest! And there is no doubt that quantity is a main factor in creating a sense of satiety.

- Taste Satisfaction and Perception
Another factor that determines a sense of satiety is taste satisfaction. Fruits and vegetables have much more intense, complex and varied flavors than do grains and cereals (unless these are seasoned with condiments) and thus offer our taste palette more assortment. A weight management idea proposed inventing a sort of artificial food in the form a spray in different flavors that would induce a sense of fullness!
Taste is also a sense that is stimulated by contact with the taste buds and by smell, thus if a food stays longer in the mouth and eating is accompanied by proper respiration, this increases the sense of satisfaction exponentially comparing to when one eats in a rush, without taking time to masticate correctly and while hardly breathing. We often talk about a perception of taste that is imagined and not real, such as when we see a food behind a store window yet it seems as if we could smell it...
People who have weight problems tend to eat quickly, chew little and use large amounts of salt on their food, perhaps to compensate for the lack of flavor due to the fact that the food spends little time in contact with their taste buds.
Just take for example egg eaters in the Guinness Book of World Records. They proceed by swallowing the eggs whole and quickly in order to prevent a feeling of fullness from setting in that would heighten feelings of disgust. It's an extreme example but the basic concept is the same.

We have pointed out that foods with a low calorie content tend to have a high concentration of micronutrients, the very ones that determine the nature and intensity of a flavor. Meanwhile, foods such as grains and cereals, especially processed and refined grains and cereals, have a bland, neutral flavor and high calorie content. Bread, for example, is not very filling and we tend to eat large quantities of it without even realizing it.

- Fiber Content
Because of its flavor and ability to create volume, fibers tend to stimulate a sense of satiety. Fibers are actually complex carbohydrates that are indigestable for humans because our bodies do not possess the enzyme to break apart the monosaccharides that make up fibers. For example if you try eating white and whole wheat bread you will notice how you are able to eat a larger quantity of the white bread without feeling full.

The Right Amount

As in all things, it is important to find the right balance also in our diets. Should we go back to eating like the prehistoric man, raw vegetables and wild game? It would be interesting but an unlikely trendsetter.
A more realistic approach would be to pay more attention to the quality and types of carbohydrates we choose to consume. Carbohydrates should not be eliminated from our diets because they are a real part of today's world, but our consumption of it should definitely be significantly less than what we are accustomed to. Furthermore, the carbs that we do consume should, whenever possible, come from low calorie content sources and we should favor whole foods rather than processed versions.
Particular attention should be paid to breads. While our consumption of pasta or rice is usually limited to the portion that we have in our plate, our consumption of bread is often unlimited. We should get into the habit of setting aside a portion of bread (two or three slices) and limit ourselves to those at one meal. Substituting bread is also a smart idea. Potatoes are an alternative to bread, eating both in one meal makes no sense. Crackers and unleavened breads are also good substitutes and we are less likely to eat large amounts of these.

The most important step however is to significantly increase the amount of vegetables at each meal. I often notice groups of people dining together sharing from a bowl of salad that would actually be the proper portion for only one person. Increasing the consumption of vegetables also means having less room in our stomachs for grains and starches.

Another aspect to consider is that there are significant differences also between different types of cereals and grains. One of these types that we are rediscovering nowadays is kamut, a grain that contains more protein than does regular wheat (about 17% comparing to 12% in wheat). It is interesting on a micronutritional level also because of its selenium content. Kamut is normally organically grown.

The aim of this article is to encourage us to begin questioning some of those habits that may seem absolutely normal, like following a daily diet based on pasta and baked goods, and that these habits should be less conditioned by commercials and advertisements that, for obvious reasons, tend to promote sophisticated and elaborate products instead of simple, basic foods.

05/08/2008