Fundamentals of Human Nutrition/Defining Carbohydrates

< Fundamentals of Human Nutrition

4.1 Defining CarbohydratesEdit

4.1.1 Introduction to CarbohydratesEdit

Carbohydrates are often given a bad report, even by doctors who certainly should know better. This misconception only serves to further confuse an already muddled public.
The confusion comes about when we try to lump all carbohydrates into one category and fail to differentiate between the different types.
On the other hand, when a differentiation is made, it is often only between two types of carbohydrates: simple and complex. This even further muddles the discussion. In this section we will be discussing three types of carbohydrates:
  1. Complex
  2. Simple
  3. Processed simple
First, we will start with the source of all carbohydrates. All carbohydrates originate from plants. Carbohydrates have one purpose, and that is to create glucose in the blood,hence the reason for proteins and fats not being listed on the glycemic index. The glucose is then transported through the blood to the mitochondria of each cell where it is used to produce the energy molecule, adenosine triphosphate. Without this high energy molecule, there would be no energy for life's processes. Proteins and fats, the other two macronutrients covered later in this text do not do this. They are digested in a different manner.

4.1.2 Simple SugarsEdit

This group of foods may include vegetables like kale, spinach, broccoli, collard greens,and mustard greens. These are said to be the dark green vegetables. Within these plants you find every vitamin, water soluble or fat soluble known to man. Phyto-meaning plant-chemicals are those compounds science has recently discovered that have protective properties against degenerative diseases such a cancer. These compounds are found only within this treasure chest of preventative medicines of nature. Grains like brown rice are an example of another plant grown for human consumption that falls into the complex carbohydrate category. The reason vegetables still look like vegetables by the time they get to the consumers' table and brown rice remains brown is because they are not subjected to the extreme milling process that produces flour. There are three layers to the rice kernel, husk or hull,(for protection and has no nutrients) bran layer, endosperm, and the embryo. During milling only the husk is removed. The brown bran layer, containing all the vitamins and minerals is left intact.


Definition : Sweet, colorless, crystalline structure which contain one (mono) molecule of sugar (saccharide), with the basic CnH2nOn makeup. One of the smallest units in the class of carbohydrates and they cannot be decomposed by hydrolysis. [1]

There are two of these sugars and they are Fructose and Glucose [2] followed here in detail:


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Glucose Also known as blood sugar and Dextrose. It is made in plants by photosynthesis, whereby the light energy works with chlorophyll in chloroplasts to convert CO2 to Glucose. It is structurally, C6H12O6. This the same as Fructose as discussed in the next section. This sugar is an aldehyde, however. It requires no digestion to be absorbed by humans, thus its use for intravenous feeding.


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Fructose Also known as fruit sugar, or called earlier, aslevulose[3]. It is an isomer of Glucose found in plants and honey. Honey was turned into Fructose by the bee's enzyme converting by hydrolysis, the compound, Sucrose (the combination of these two simple sugars discussed, and below under Polysaccharides as a Disaccharide.) As mentioned above, it also has C6H12O6 for its structure, but the linear construction is different because it is a ketone.


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4.1.3 Complex carbohydratesEdit

Complex carbohydrates form one of the main dietary components. Carbohydrates are one of the three essential macronutrients required for the full functioning of the human body. They include sugars, starches, and fibers. Simple carbohydrates are sugars while complex carbohydrates include starch and fiber. They provide energy for the body, especially the brain and the nervous system. The energy is also used for functions like heartbeat, digestion, breathing and body movement. An enzyme, amylase, breaks down the carbs into glucose that is used for energy. Starch in food must be broken down through digestion before the body can use it as a dietary source.

Complex carbohydrates consist of sugar molecules stuck together in long chains and branches. The body turns both simple and complex carbohydrates into glucose (blood sugar). Glucose is used in the cells of the body and in the brain. Any unused glucose is stored in the liver and muscles as glycogen for use later. Due to their complexity, complex carbohydrates take a little longer to digest, and they don't raise the sugar levels in the blood as quickly as simple carbohydrates. They act as the body's fuel, and they contribute significantly to energy production.

They are found in a variety of foods, including grains, vegetables and legumes - Examples of foods that contain complex carbohydrates include spinach, yams, broccoli, beans, zucchini, lentils, skimmed milk, whole grains, like, millet, oats, wheat germ, barley, wild rice, brown rice, buckwheat, oat bran, cornmeal, amaranth and many other leguminous plants and vegetables. Complex carbohydrates, such as whole grains, contain more nutrients and fiber than simple carbohydrates, such as sugar. Products made from these grains are complex too, like, grain bread, pasta, bagels, buns and rolls, macaroni, breakfast cereals. Complex carbohydrates are also low-glycemic, meaning they have a mild impact on your blood sugar and can enhance appetite control, weight management and energy.

Complex carbohydrate foods provide vitamins, minerals, and fiber that are important to the health of an individual. The majority of carbohydrates should come from complex carbohydrates (starches) and naturally occurring sugars, rather than processed or refined sugars, which do not have the vitamins, minerals, and fiber found in complex and natural carbohydrates. Refined sugars are often called "empty calories" because they have little to no nutritional value.

The daily recommendation for dietary fiber, 14 grams for every 1000 calories, is not met by most of the people. Breads, rolls, buns and pizza crust made with refined flour are not among the best sources of fiber which is consumed in large proportions. Instead, people need to increase consumption of beans, peas, vegetables, fruits, whole grains, nuts, seeds and foods with natural fiber. Some dairy products, like, low fat milk, low fat yogurt and skim milk are also good choices for complex carbohydrates in diet.

Complex carbs can be calculated - %Complex carb = (Dietary fiber + Starch) / Total Carbohydrates. Some examples of complex carb percentage are (1) 95.3% in Potatoes, white, flesh and skin, baked, (2)

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Complex carbohydrates include disaccharides and polysaccharides. The main disaccharides include three pairs of monosaccharides, of which are Maltose, Sucrose and Lactose. All three of these disaccharides include a glucose bonded to either another glucose, a fructose or a galactose, respectively. Sucrose is table sugar and lactose is found in dairy products. Polysaccharides are much more complicated and can involve multiple units of glucose or even multiple strings of monosaccharides. [1] Most all dietary fibers are polysaccharides.

Disaccharides are two monosaccharides bonded together by a covalent bond. [2] In a journal article titled “Effect of Diet upon Intestinal Disaccharidases and Disaccharide Absorption” a group of laboratory rats were put on a fast for 3 days and then fed either a high sucrose diet (a disaccharide rich diet) or casein, used as a control group in this study. The group fed a disaccharide rich diet was observed to have extremely heightened sucrase and maltase activity. [4] This shows that disaccharides and a high dose of them can affect one's intestinal tract as well as absorption of other disaccharides and polysaccharides.

Polysaccharides fall into two main groups, starches that are made exclusively from plant matter and glycogen made from animals. Cellulose is another common polysaccharide and it is made from the cell walls of plants and consist of long chains of glucose. However animals cannot digest this type of polysaccharide, as it contains beta bonds that need a certain enzyme present to be digested. Humans do not have this enzyme in their digestive system, which is why cellulose is not considered a nutrient and humans do not eat wood to get their glucose. For glycogen and starch, the main purpose in humans is readily available storage of glucose. When more glucose is consumed than needed at the moment, the liver will store the excess as glycogen. Then at a later time, when glucose levels are low, the liver will convert the stored glycogen back into glucose ready for use. [2] Starches are a polysaccharide that contain 300 to 1000 units of glucose bonded together. As mentioned earlier, starches come from plants, and is formed within a grain. These grains contain a hard outer layer. Humans can digest starches as they are smaller molecules that cellulose and more bioavailable to be used for energy. [5] A study in the IEEE scientific journal on certain types of fungi in China and the polysaccharides extracted from them revealed that the polysaccharides contain anti-aging properties as well as anti-infection and anti-tumor properties. [3]

[1] Ophardt, C., (2003) Di-, Poly-Carbohydrates - Introduction. Retreived from

[2] Austin Community College, (2015) Carbohydrates. Retrieved from

[3 Song, G., Du, Q., (2011) Antioxidant Activity Comparison of Polysaccharides from Nine Traditional Edible Fungi in China. Retrieved from

[4] Deren, J., Broitman, S., Zamcheck, N., (1967) Effect of Diet upon Intestinal Disaccharidases and Disaccharide Absorption. Retrieved from

[5] Hyperphysics, (2015) Carbohydrates. Retrieved from