NutritionFactsandFiction.com

With all the talk and attention given to diets and dieting these days, it is easy to lose sight of of the most important component of food intake and that is nutrition. The fact is, what we put into our bodies has a very important impact not only on how much we weigh, but also, and perhaps more importantly, on how we look and feel.

Before we go on to talk specifically about nutrition, we need to begin by talking about food itself. We all know that food is essential to life. That unless we eat some food each day we will suffer from hunger, weakness... even starvation...

If you have ever wondered about food and how your body uses it, then read on. In this section of the site, we'll give you all of the information you need to understand what a hamburger or a banana does to keep your body running every day!

Think about some of the things you have eaten today -- maybe cereal, bread, milk, juice, ham, cheese, an apple, potatoes... All of these foods (and pretty much any other food that you can think of) contain seven basic components:

Your body's goal is to digest food and use it to keep your body alive. In the following sections, we will look at each of these basic components to understand what they really do and why they are so important to your body.

(Note that there might be a few non-food things mixed in with what you eat, especially if you are eating lots of processed foods. Things like artificial colors and chemical preservatives are the most common. Those are additives, not part of the natural foods.)

You have probably heard of "carbohydrates" and "complex carbohydrates." Carbohydrates provide your body with its basic fuel. Your body thinks about carbohydrates like a car engine thinks about gasoline.

The simplest carbohydrate is glucose. Glucose, also called "blood sugar" and "dextrose," flows in the bloodstream so that it is available to every cell in your body. Your cells absorb glucose and convert it into energy to drive the cell. Specifically, a set of chemical reactions on glucose creates ATP (adenosine triphosphate), and a phosphate bond in ATP powers most of the machinery in any human cell. If you drink a solution of water and glucose, the glucose passes directly from your digestive system into the bloodstream.

The word "carbohydrate" comes from the fact that glucose is made up of carbon and water. Glucose is a simple sugar, meaning that to our tongues it tastes sweet. There are other simple sugars that you have probably heard of. Fructose is the main sugar in fruits. Fructose has the same chemical formula as glucose (C₆H₁₂O₆), but the atoms are arranged slightly differently. The liver converts fructose to glucose.

Sucrose, also known as "white sugar" or "table sugar," is made of one glucose and one fructose molecule bonded together. Lactose (the sugar found in milk) is made of one glucose and one galactose molecule bonded together. Galactose, like fructose, has the same chemical components as glucose but the atoms are arranged differently. The liver also converts galactose to glucose. Maltose, the sugar found in malt, is made from two glucose atoms bonded together.

Glucose, fructose and galactose are monosaccharides and are the only carbohydrates that can be absorbed into the bloodstream through the intestinal lining. Lactose, sucrose and maltose are disaccharides (they contain two monosaccharides) and are easily converted to their monosaccharide bases by enzymes in the digestive tract. Monosaccharides and disaccharides are called simple carbohydrates. They are also sugars -- they all taste sweet. They all digest quickly and enter the bloodstream quickly. When you look at a "Nutrition Facts" label on a food package and see "Sugars" under the "Carbohydrates" section of the label, these simple sugars are what the label is talking about.

There are also complex carbohydrates, commonly known as "starches." A complex carbohydrate is made up of chains of glucose molecules. Starches are the way plants store energy -- plants produce glucose and chain the glucose molecules together to form starch. Most grains (wheat, corn, oats, rice) and things like potatoes and plantains are high in starch.

Your digestive system breaks a complex carbohydrate (starch) back down into its component glucose molecules so that the glucose can enter your bloodstream. It takes a lot longer to break down a starch, however. If you drink a can of soda full of sugar, glucose will enter the bloodstream at a rate of something like 30 calories per minute. A complex carbohydrate is digested more slowly, so glucose enters the bloodstream at a rate of only 2 calories per minute.

You may have heard that eating complex carbohydrates is a good thing, and that eating sugar is a bad thing. You may even have felt this in your own body. The following quote from The Yale Guide to Children's Nutrition explains why:

If complex carbohydrates are broken down to monosaccharides in the intestines before they are absorbed into the bloodstream, why are they better than refined sugar or other di- or mono-saccharides? To a great extent it has to do with the processes of digestion and absorption. Simple sugars require little digestion, and when a child eats a sweet food, such as a candy bar or a can of soda, the glucose level of the blood rises rapidly. In response, the pancreas secretes a large amount of insulin to keep blood glucose levels from rising too high.

This large insulin response in turn tends to make the blood sugar fall to levels that are too low 3 to 5 hours after the candy bar or can of soda has been consumed. This tendency of blood glucose levels to fall may then lead to an adrenaline surge, which in turn can cause nervousness and irritability... The same roller-coaster ride of glucose and hormone levels is not experienced after eating complex carbohydrates or after eating a balanced meal because the digestion and absorption processes are much slower.

If you think about it, this is incredibly interesting because it shows that the foods you eat and the way you eat them can affect your mood and your temperament. Foods do that by affecting the levels of different hormones in your bloodstream over time.

Another interesting thing about this quote is its mention of insulin. It turns out that insulin is incredibly important to the way the body uses the glucose that foods provide. The functions of insulin are:

Insulin is a simple protein in which two polypeptide chains of amino acids are joined by disulfide linkages. Insulin helps transfer glucose into cells so that they can oxidize the glucose to produce energy for the body. In adipose (fat) tissue, insulin facilitates the storage of glucose and its conversion to fatty acids. Insulin also slows the breakdown of fatty acids. In muscle it promotes the uptake of amino acids for making proteins. In the liver it helps convert glucose into glycogen (the storage carbohydrate of animals) and it decreases gluconeogenesis (the formation of glucose from noncarbohydrate sources). The action of insulin is opposed by glucagon, another pancreatic hormone, and by epinephrine.

What you can begin to see from this description is that there are actually lots of different things happening in your body around glucose. Because glucose is the essential energy source for your body, your body has many different mechanisms to ensure that the right level of glucose is flowing in the bloodstream. For example, your body stores glucose in your liver (as glycogen) and can also convert protein to glucose if necessary. Carbohydrates provide the energy that cells need to survive.

Before we move on to talk about the other food basics, I think it is important here, while we are talking about energy and glucose, to talk a bit about exactly what part this breakdown of carbohydrates actually plays in our daily existence.

A normal person who is eating three meals a day and snacking between meals gets almost all of his or her energy from the glucose that carbohydrates provide. What happens if you stop eating, however? For example, what if you are lost in the woods, or you are purposefully fasting? What does your body do for energy? Your body goes through several phases in its attempt to keep you alive in the absence of food.

The first line of defense against starvation is the liver. The liver stores glucose by converting it to glycogen. It holds perhaps a 12-hour supply of glucose in its glycogen. Once you finish digesting all of the carbohydrates that you last ate, the liver starts converting its stored glycogen back into glucose and releases it to maintain glucose in the blood. Lipolysis also starts breaking down fat in the fat cells and releasing fatty acids into the bloodstream. Tissues that do not need to use glucose for energy (for example, muscle cells) start burning the fatty acids. This reduces the glucose demand so that nerve cells get the glucose.

Once the liver runs out of glycogen, the liver converts to a process called gluconeogenesis. Gluconeogenesis turns amino acids into glucose. The liver then begins producing ketone bodies from fatty acids being made available in the blood by lipolysis. Brain and nerve cells convert over from being pure consumers of glucose to partial consumers of ketone bodies for energy.

Some of these alternative metabolic processes are actually used on a regular basis. For example, Eskimos eating a traditional Eskimo diet have virtually no carbohydrates on the menu. You may have also read about several recent weight-loss programs that try to take advantage of ketone metabolism to "burn fat". When you hear about these diets you will now have a better idea of what they're about!

One other food fact you may find intriguing: it is not our stomach that regulates how we sense hunger, but rather a small brain structure called the hypothalamus. If one part of the hypothalamus is damaged, a person will overeat tremendously. If another part is damaged, a person never gets hungry. So clearly these two parts balance one another to produce our sense of hunger. And this is a key organ to target for dietary intervention.

Nutrition Facts and Fiction