Carbohydrates give us energy. We need energy to do everything we do, whether we think about it or not, like going for a walk, working or sleeping. Even when we don’t think about it, our body is busy keeping our heart pumping, blood flowing and lungs working. We always need energy. We need even more energy when we are growing, getting well and pumping up.
Our body’s favorite supply of energy comes from carbohydrates. We can get energy from other nutrients like protein and fat, but protein needs to be saved for building our body and keeping it working well. We don’t want to get more fat than we need because, if we do, fat gives us saturated fat, a kind of fat that is not healthy. Carbohydrate foods are also generally low in fat, depending on how they are prepared and what is added to them at the table. Carbohydrates also protect against wasteful breakdown of body protein to supply energy, and carbohydrates also provide flavor and sweetness to foods. The body needs carbohydrates to use fat efficiently.
In this lesson, you will learn what carbohydrates are. You will also learn about the different types of sugars that form carbohydrates and the difference between simple and complex carbohydrates. You will learn how much carbohydrates should be eaten in a day.In this lesson, you will learn the following:
Carbohydrates are compounds made up of carbon, hydrogen and oxygen. Carbohydrates come from plants. Plants use carbon dioxide, water and energy from the sun to produce the carbohydrates we eat. Most are known as sugars, starches and fiber. Sugars and starches give us energy. Since dietary fiber is not absorbed by the body, it is not a source of energy. Carbohydrates make our food sweet. Carbohydrates are classified into three categories: simple carbohydrates, complex carbohydrates and dietary fiber.
There are three main kinds of carbohydrates: (1) simple carbohydrates or simple sugars such as table sugar and the sugar in milk, (2) complex carbohydrates such as starches and (3) dietary fiber.
Simple Sugars (Monosaccharides and Disaccharides):
Simple sugars are made up of two classes of sugars based on their chemical structure. Sugars having one molecule or one sugar are called monosaccharides, and sugars made up of two monosaccharides are called disaccharides. Both are referred to as simple sugars.
Monosaccharides is another name for simple sugars or simple carbohydrates. Mono means one and saccharide means sugar. Glucose, fructose and galactose are monosaccharides.
1. Glucose, also called blood sugar or dextrose, is the main monosaccharide in your body. Glucose was named after the Greek word meaning sweet.
2. Fructose, also called levulose, is found in fruit, honey and high-fructose corn syrup. Honey is made up of about half fructose and half glucose. High-fructose corn syrup is found in soft drinks, frozen desserts and candies.
3. Galactose is not generally found free in nature in large amounts. It combines with glucose to form a double sugar called lactose. Lactose is in milk and in other dairy products. Lactose is what gives milk its sweet taste. Once absorbed into the body, galactose is either changed into glucose or made into a storage form of glucose in the liver and muscle, called glycogen.
Once the monosaccharides glucose, fructose and galactose are absorbed by way of the small intestine and enter the liver, much of the fructose and galactose is tuned into glucose.
Disaccharides or double sugars
Disaccharides is another name for simple sugars or simple carbohydrates. “Di” means two.
Disaccharides are formed when two monosaccharides combine. Three disaccharides common in the diet are maltose, sucrose and lactose.
1. Maltose is made when two glucose molecules are combined during the process of starch in grains breaking down during germination.
2. Sucrose or table sugar is made up of glucose and fructose. Sucrose comes from sugarcane, sugar beets, honey and maple syrup. You might use brown, white or powdered sugars in cooking, eating or adding to beverages. These forms of sugar are based on the degree the sucrose is purified from the plant source.
3. Lactose is glucose joined to galactose to form the sugar found in milk and dairy products. Some people are not able to digest large amounts of lactose. This can cause intestinal gas, bloating, cramping and discomfort as any unabsorbed lactose is metabolized into acids and gases by bacteria in the large intestine. Once absorbed into the body, the majority of these carbohydrates are changed into glucose by the liver.
Oligosaccharides contain three to ten single-sugar units. Oligo means scant. Two of nutritional importance include raffinose and stachyose. These are made of monosaccharides but are bonded together in such a way that the digestive enzymes our bodies make cannot break them down. When we eat these carbohydrates in beans and other legumes, the raffinose and stachyose molecules remain undigested as they reach the large intestine. Bacteria in the large intestine then break them down producing gas and other byproducts.
Polysaccharides (starch and complex carbohydrates)
Polysaccharides are composed almost entirely of long strands of only one monosaccharide – glucose. Hundreds of glucose units are connected together to form starch. Starch and complex carbohydrates are the main terms used for the major digestible polysacccarides in our diet. The storage form for carbohydrates in our body is glycogen. When our body needs glucose, the glycogen stored in the liver is turned into blood glucose.
Complex Carbohydrates: Also know as polysaccharides (poly = many), these carbohydrates have more than two units of glucose (sugar) linked together. Polysaccharides are generally not sweet and are not water soluble. Starches and dietary fiber are complex carbohydrates.
Dietary carbohydrates are the main source of energy for the body, including digestion and absorption of other foods. Although proteins and fats can be converted into energy, carbohydrates are the body’s preferred source of energy. Dietary carbohydrates also help in fat metabolism and the formation of nonessential amino acids. In combination with proteins, carbohydrates form substances that are essential to fighting infection, lubricating the joints and maintaining the health and growth of bones, skin, nails, cartilage and tendons. Carbohydrates are components of cell membranes, and they function as antibodies. They form part of cell membranes particularly in the brain and the nervous system.
As an energy source, one gram of carbohydrate yields four calories.
Dietary fiber regulates gastrointestinal transit time, and it facilitates efficient elimination. Proper elimination reduces abdominal pressures that can cause hemorrhoids and certain types of hernia. Appendicitis may be associated with inadequate fiber content in the diet, too.
A high-fiber diet reduces the rate of colon and rectal cancers by allowing carcinogens in the food to move more quickly through the intestinal tract. Colon cancer might be caused by carcinogens in bile and an increase in anaerobic bacteria, both directly related to high levels of saturated fat and low intake of fiber in the diet. Reducing these chronic diseases can be done by dietary means: reduction of saturated fats and an increase in whole grains, fruits, vegetables and legumes.
Of total caloric intake, 45% - 65% should come from carbohydrates. The exact intake in grams will vary, depending on the caloric level of an individual. The Estimated Average Requirement (EAR) for carbohydrate is 130 grams per day for adults and children based on the glucose needs of the brain. The Adequate Intake (AI) for fiber is 14 grams per 1,000 calories consumed (28 grams for 2,000 calories).
What counts as 1 ounce-equivalent from the Grain Group?1 slice of bread 1 ounce of ready-to-eat cereal 1/2 cup of cooked cereal, rice or pasta
The 2010 Dietary Guidelines for Americans recommends that we should make at least half of our grains whole grains. To ensure that you are choosing foods that contain whole grains, choose foods that name one of the following whole-grain ingredients first on the label's ingredient list:
brown rice whole-grain corn
buckwheat whole-grain sorghum
bulgur whole-grain triticale
millet whole oats
oatmeal whole rye
quinoa whole wheat
rolled oats wild rice
Use these suggestions to add carbohydrates to your diet:
1. Join the breakfast club. Choose from many convenient choices such as cereal, English muffins, bagels, waffles, pancakes and toast. Choose whole wheat!
2. Get cracking. Keep a box of crackers or pretzels and some fruit around to curb hunger pangs with carbohydrates.
3. Bag it. Put dry cereal in a plastic bag and take it along for a quick snack or breakfast on the run. Eat it plain or mix it with yogurt or skim milk if kept cold.
4. Curl up with a tortilla. Toss low-fat cheese on a tortilla and pop it in the microwave for a few seconds. Roll it up and dip it in salsa for a healthy, fast snack. Or spread a tortilla with low-fat peanut butter and jelly and roll it.
5. Satisfy your sweet tooth with tasty carbohydrates. Try angel food cake, fig bar cookies, animal crackers and graham crackers.
6. Bag up mini-bagels for an energy-rich snack to eat on the run.
7. Use whole-grain breads for lunch or snacks.
8. Try low-fat granola-type cereals as a topper for fruit-flavored or frozen yogurt.
9. Try whole-wheat pasta.
See if you know the answers to these questions and write them down:
1. Some of the different kinds of sugars end with the same three letters. What are these three letters?
2. List the names of the different kinds of sugars that end with these three letters.
3. If you look at a list of ingredients on a food label, what word ending with these three letters would tell you that that ingredient is sugar?
4. Which foods are sources of fructose and galactose?
All starchy foods are plant foods. Major food sources of starch include grains, legumes (beans and peas), potatoes and sweet potatoes. Other good carbohydrate foods include pastas and vegetables. When you eat these starchy foods, enzymes in your mouth and intestine hydrolyze or break down the starch molecule to release glucose units and water, which are absorbed across the intestinal wall into the blood. One to four hours after a meal, all the starch has been digested and is circulating to the cells as glucose.
Foods that are complex carbohydrates are also some of our least-expensive foods! We need to reduce our intake of concentrated sweets and food or beverages with a lot of sugar added. These include sweets and beverages that have little or no nutritive value and give primarily calories. Instead, we need to eat more complex carbohydrates such as grains, legumes, potatoes and other vegetables and pasta and eat more naturally occurring sugars (fruits, vegetables and dairy products). Read the Nutrition Facts label on food packages. Look to see what percentage of calories from carbohydrate the food provides. The percentage of calories from carbohydrate is more important than the total grams of carbohydrate in a particular food. The carbohydrate content of foods can be diluted either by protein, as the case in skim milk, or by fat, as in a cream pie. Select a nutrient-dense carbohydrate food to get more nutrition bang for the buck.
Monosaccharides and disaccharides are often referred to as simple sugars. Food labels sometimes lump all these sugars under that one category, listing them as sucrose and other sugars. The nutrition label on a food package does not list a Percent Daily Value (% Daily Value) for sugars. There is no scientific proof to indicate that a particular amount of sugars in the diet is appropriate or inappropriate. Other than dental caries or cavities, there is no evidence that sugar intake is associated with chronic disease conditions.
The ingredient list tells you exactly what is in a food. Ingredients are listed by weight from most to least. Those in the largest amounts are listed first. Ingredients that are sugars may be listed as different words. Many of these end with three letters ose. These include lactose, maltose, glucose, sucrose, fructose, dextrose, polydextrose and levulose. Other names of sugars used in foods include brown sugar, confectioner’s sugar, turbinado sugar, invert sugar, sorbitol, mannitol, honey, corn syrup or sweeteners, high-fructose corn syrup, molasses, date sugar, maple syrup, dextrin, caramel and fruit sugar.
A number of popular diets are low in carbohydrates. Some suggest that carbohydrates are “bad” and unnecessary; others emphasize high carbohydrate intake.
Thousands of “low-fat” alternatives now crowd the supermarket shelves. But simply cutting back on fat and loading up on carbohydrates may not be a healthy way to eat or lose weight, according to research. Just as not all types of fat are bad, not all types of carbohydrates are good.
Gram for gram, fat has more than twice as many calories as either protein or carbohydrates. Yet all too often the low-fat products on supermarket shelves are packed with sugar and highly processed carbohydrates to make up for the taste that’s lost when fat is removed. These low-fat alternatives often have just as many calories as the full-fat versions and may even have more.
In theory, a high-protein/low carbohydrate diet could help increase satiety, the feeling of fullness that comes with eating. Fewer carbohydrates could also avoid fast and high rises, and falls, in blood sugar, which may also keep hunger at bay. Together, these could help avoid overeating and make one satisfied with fewer calories.
In a review of low-carbohydrate diets, it was shown that low-carbohydrate diets were safe in the short term but that weight loss was due mostly to reduced caloric intake, not necessarily to the low-carbohydrate nature of the diets. Such reductions often happen when people drastically change what they eat.
Until more is known about diets that manipulate macronutrient ratios, it is best to follow the USDA’s 2010 Dietary Guidelines for any diet, whether reduced-calorie or not.
Some of the most common nonintuitive sweeteners include:
Saccharin (Sweet ’n Low) – provides no calories and is 200 times sweeter than sugar. It was banned by the FDA until consumers rallied in support. Today a statement has to be added to foods that have saccharin that states that it can cause cancer in laboratory animals.
Aspartame (Equal) – is composed of two amino acids and provides 1 calorie/tsp. It is 180-220 times sweeter than sugar. Aspartame may cause headaches in sensitive individuals. Heat denatures aspartame, and therefore it cannot be used in foods that need to be cooked.
Acesulfame K – provides no calories and is about 200 times sweeter than sugar. It is heat-stable and can be used in foods that need to be cooked or heated.
Sucralose (Splenda) – a fairly new product derived from table sugar. It is 600 times sweeter than sugar and is stable at high temperatures. Rebiana & Erythritol (Truvia) – a new product made from the stevia plant. One packet is said to contain sweetness equivalent to 2 teaspoons of regular table sugar.
Choose a diet with plenty of grain products, vegetables and fruits. They give you carbohydrates, a nutrient that gives you the get up and go! Carbohydrate foods are also generally low in fat, depending on how they are prepared and what is added to them at the table.
Follow the Dietary Guidelines and MyPlate to eat healthy and stay healthy every day. To fuel up on carbs, have 6 ounce-equivalents from the grain group, 2.5 cups from the vegetable group, and 2 cups from the fruit group every day (for a 2,000-calorie diet). For other important nutrients, eat 3 cups from the dairy group and 5.5 ounce-equivalents from the protein group. Foods that are complex carbohydrates are also some of our least-expensive foods! Major food sources include grains, legumes (beans and peas), potatoes and sweet potatoes. For more nutritive value, eat more naturally occurring sugars that are in fruits, vegetables and milk instead of concentrated sugars in candy, cookies and soft drinks.
Read the Nutrition Facts label on food packages. Look to see what percentage of calories from carbohydrate the food provides. The percentage of calories from carbohydrate is more important than the total grams of carbohydrate in a particular food.
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