Before you watch, discuss with your partner the saying “You are what you eat”. Do you agree with it?

Now watch the clip and be ready to say why nutrition is important.

Before you read

You are going to read an article about the basics of food. What do you know about it?

It is safe to say that one thing you’ll do today is eat some food – food is essential to life. But what is food? What’s in food that makes it so important? What is food made of? How does it fuel our bodies? Discuss with your partner the above-mentioned questions. How many of them can you answer?

3. Skim^{^[1]} the text to check your ideas.

Reading A

THE BASICS OF FOOD (PART I)

by Marshall Brain

Food is any substance consumed to provide nutritional support for the body. Think about some of the things you have eaten today – maybe cereal, bread, milk, juice, ham, cheese, an apple, potatoes... All of these foods are usually of plant or animal origin and contain seven basic components or essential nutrients: carbohydrates (simple and complex), proteins, fats, vitamins, minerals, fiber, and water. The food is ingested by an organism and assimilated by the organism’s cells in an effort to produce energy, maintain life, and/or stimulate growth. So, your body’s goal is to digest food and use it to keep your body alive. Let’s look at each of these basic components to understand what they really do and why they are so important to your body.

Carbohydrates

Carbohydrates provide your body with its basic fuel. The simplest carbohydrate is glucose. Glucose, also called “blood sugar”, 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.

The word “carbohydrate” comes from the fact that glucose is made up of carbon and water. The chemical formula for glucose is: C₆H₁₂O₆. Glucose is a simple sugar, meaning that to our tongues it tastes sweet. There are other simple sugars: fructose (the main sugar in fruits), sucrose (also known as “white sugar” or “table sugar”), lactose (the sugar found in milk), galactose, and maltose (the sugar found in malt).

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 and are also sugars. They all digest quickly and enter the bloodstream quickly.

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. A complex carbohydrate is digested more slowly, so glucose enters the bloodstream at a rate of only 2 calories per minute.

Insulin is incredibly important to the way the body uses the glucose that foods provide. It is a simple protein in which two polypeptide chains of amino acids are joined by disulfide linkages. It 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.

Proteins

A protein is any chain of amino acids. An amino acid is a small molecule that acts as the building block of any cell. Carbohydrates provide cells with energy, while amino acids provide cells with the building material they need to grow and maintain their structure. Your body is about 20-percent protein and about 70-percent water by weight. Most of the rest of your body is composed of minerals (for example, calcium in your bones). Amino acids are called “amino acids” because they all contain an amino group (NH₂) and a carboxyl group (COOH), which is acidic. The human body is constructed of 20 different amino acids.

As far as your body is concerned, there are two different types of amino acids: essential that your body can create out of other chemicals found in your body and non-essential that cannot be created, and therefore the only way to get them is through food. Here are the different amino acids: non-essential (alanine, arginine, asparagines, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine); essential (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine).

Protein in our diets comes from both animal and vegetable sources. Most animal sources (meat, milk, eggs) provide what’s called “complete protein”, meaning that they contain all of the essential amino acids. Vegetable sources usually are low on or missing certain essential amino acids. However, different vegetable sources are deficient in different amino acids, and by combining different foods you can get all of the essential amino acids throughout the course of the day. Some vegetable sources contain quite a bit of protein – things like nuts, beans, soybeans, etc. are all high in protein.

The digestive system breaks all proteins down into their amino acids so that they can enter the bloodstream. Cells then use the amino acids as building blocks.

Carbohydrate, protein, and fat are the main sources of calories in the diet and are called macronutrients. Both carbohydrates and proteins provide 4 calories per gram.

http://recipes.howstuffworks.com/food.htm

Reading Comprehension

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