Basic Nutrition Lesson One - Carbohydrates

An Introduction to Carbohydrates

What are carbohydrates? Carbohydrates are the main source of energy for the body. Those carbohydrates come from the plant-based foods that you eat. You can either use carbohydrates right away for your energy needs or your body can convert them into fat to use later. There are three types of carbohydrates - sugars, starches and fiber.

First, a Little Chemistry

No matter how big they are, all carbohydrates are made up of carbon, hydrogen and oxygen with the general formula of Cm(H2O)n. For example, a simple little sugar molecule like glucose is made up of six carbon atoms, 12 hydrogen atoms and 6 oxygen atoms. It is shaped like a hexagon and has the formula C6(H2O)6. A large starch molecule can be made out of many little sugar molecules attached together, which forms a long chain.The little m and n in our general formula, Cm(H2O)n, can run into the hundreds.

Simple Sugars

Simple sugars are little molecules made up of one or two sugar units. In nutrition, the most basic simple sugar is glucose, C6(H2O)6, and it is the type of sugar our bodies and brains use for energy every day. Glucose is called a monosaccharide, which means "single sugar.” Other monosaccharides include fructose, galactose, and ribose. Fructose is found in fruits and in vegetables, galactose is found in milk and ribose is best known as a component in ribonucleic acid, which is a part of genetic transcription and is found in the cells in our bodies.

I don't want to get much deeper into the chemistry of simple sugars, but it is important to know that the single sugars glucose, fructose and galactose can form different combinations to become disaccharides, a term that means "two sugars.” These sugars include:

Lactose (milk sugar) is made up of glucose and galactose molecules. People who are "lactose intolerant" can't digest this sugar properly.
Sucrose (table sugar) is made up of glucose and fructose molecules. This is the white powdery or granular substance we typically refer to as "sugar" when we are cooking or baking.
Maltose (malt sugar) is produced during the malting of cereals such as barley.

Simple sugars are water-soluble and sucrose, or table sugar, is very easy to digest. The individual glucose and fructose molecules are quickly absorbed into the bloodstream via the small intestine. This can be a problem for people with diabetes or metabolic syndrome who have to watch their blood sugar, or blood glucose levels.

Complex Carbohydrates

Complex carbohydrates are long chains of the single sugar units. For example, the complex carbohydrate we know as starch is made up of many glucose units. These complex carbohydrates can be in the shape of long chains, or the chains can form branches. The complex carbohydrates include:

Starch is the energy storage form of carbohydrates found in plants, especially in the seeds and roots. Starch is made up of many glucose units linked together. Starchy food examples include rice, wheat, corn, carrots and potatoes. Starches are not water-soluble and require digestive enzymes called amylases to break them apart.
Glycogen is the energy storage form of glucose found in the muscles and livers of animals. You don’t consume any carbohydrates when you eat meats, however the amount of glycogen in animal tissue at the time of slaughter does affect the pH of meat.
Cellulose is the structural component of plants. Cellulose helps plants keep their shape so in a way, cellulose acts like a plant skeleton. We are not able to digest cellulose, however cellulose is one of the important components of fiber, along with lignin, chitin, pectin, beta-glucan, inulin and oligosaccharides.

Dietary starch and cellulose are the complex carbohydrates that are important in nutrition. Potatoes, dry beans, grains, rice, corn, squash and peas contain a large amounts of starch. Vegetables like broccoli, cauliflower, asparagus, lettuces and other greens are not starchy. That is because the stems and leafy parts of plants do not contain much starch, but they do contain more cellulose. Since we can't digest cellulose, that means that the green and leafy vegetables contain fewer calories than the starchy vegetables. That is important information to remember for meal planning later on.

Carbohydrates and Metabolism

The body begins the process of breaking carbohydrates down into their individual monosaccharides almost before we start to eat them. When you smell the delicious aroma of fresh-baked bread or think about that tasty chocolate that you about to consume, your mouth begins to water. Since table sugar is water soluble, it begins to dissolve in the saliva in your mouth. Your saliva also contains a small amount of amylase, which is an enzyme that starts to break starch down into glucose while you are chewing.

Carbohydrate digestion is continued in the small intestine where pancreatic amylase is secreted, which breaks down the rest of the carbohydrates. The individual monosaccharides are then absorbed into the blood stream. Once in the blood, the monosaccharides are either used for energy, stored in the liver and muscles as glycogen, or if there is more energy available than you can use, they are converted and stored as fat.

The storage of glucose is triggered by insulin, which forces your body to store any extra blood sugar as glycogen. People with diabetes or metabolic syndrome either can't produce enough insulin or they are not sensitive enough to the insulin they produce and need to regulate their blood sugar with medications, insulin or dietary changes.

Your body prefers to use glucose as the main source of fuel for daily activity. Your muscles need glucose to move and your organs need need glucose to function, including your brain. While the body can make glucose from extra dietary protein and fats you may eat, it is suggested that half of your daily calories come from carbohydrates. Try to get your carbohydrates from healthy sources such as whole grains, fruits and vegetables. Cookies, sodas, candy and other sweets are not so healthy. They may contain too many calories and unhealthy fats like trans fats. This will be important to remember later on for our healthy meal planning lesson.

Carbohydrates and Calories

An average healthy diet should have half of your daily calories coming from carbohydrates. One gram of carbohydrate, whether is it is sugar or starch, contains four calories. One slice of bread has about 12 grams of carbohydrates. One typical chocolate bar may have about 50 grams of carbohydrates. A medium potato has about 35 grams of carbohydrates.

Although all carbohydrates have four calories per gram, some sources of carbohydrates are better for your diet than others. Fruits, vegetables, legumes, nuts, seeds and grains are healthier than candy, sodas and pastries. Why? The healthy carbohydrate sources have great amounts of vitamins, minerals, phytochemicals and fiber, all of which are vital to good health. Candy, sodas, pastries and other junk foods usually are poor sources of nutrients and sometimes we refer to these foods as having “empty calories.” This means the foods have lots of calories with little or no nutrition.

Since you need half of your calories from carbohydrates, you can calculate how many you need per day. For example, let’s say a person needs 2000 calories per day. That means that 1000 calories should come from carbohydrates (2000 X 0.5). Since each gram of carbohydrate has four calories, then you divide 1000 by four (1000/4) to get 250. A person who needs 2000 calories each day needs about 250 grams of carbohydrates per day. Of those 250 grams, about 10 percent can come from added table sugar and sweeteners. That would be about 25 grams for a 2000 calorie per day diet. That would equal about half of a candy bar, or less than one can of sugary soda. Unfortunately many people exceed that amount every day.

In order to meet your carbohydrate requirement each day, you need to know how many carbohydrates are in all of the foods you eat. It really is impossible to list every carbohydrate containing food here, however, here are some approximate amounts from common examples:

One slice of bread - 12.5 grams total, of which 10 grams are starch and less than 1 gram is fiber
One cup of pasta - 43 grams total, of which 36 grams are starch and 2.5 grams are fiber
One medium apple - 19 grams total, of which 8 grams are starch and 3 grams are fiber
One Snickers candy bar - 63.5 total grams, of which 53 grams are sugar, two grams are fiber
One cup of raisin bran cereal - 43 grams total, of which seven grams are fiber, 17 grams are starch and 16 grams are sugar
One cup of sugar frosted corn flake cereal - 28 grams total, of which 15 grams are starch, one gram is fiber, 12 grams are sugar
One four ounce glass of red wine - 3 grams total, of which, less than one gram is sugar
One eight ounce serving of low fat milk - 12 grams total, of which 12 grams are lactose
One cup broccoli - 6 grams total, of which 2.5 are fiber and 1.5 are sugar
One cup green beans - eight grams total, of which four grams are fiber
One cup sweet corn - 31 grams total, of which 21 grams are starch, three grams are fiber
Two cups lettuce - 2 grams total, of which one gram is fiber
One cup asparagus - four grams total, of which two grams are fiber
One medium orange - 15 grams total, of which three grams are fiber
One half medium grapefruit - nine grams total, of which 1.5 grams are fiber
One medium chocolate chip cookie - 16 grams total, of which seven grams are sugar
One cup strawberries - 12 grams total, of which three grams are fiber
One cup blueberries - 21 grams total, of which four grams are fiber and 15 grams are sugar
One half cup marinara sauce - 14 grams total, of which less than one gram is fiber
One medium tomato - five grams total, of which 1.5 grams are fiber
One medium potato with skin - 29 grams total, of which three grams are fiber, 25 grams are starch
One cup carrots - 12 grams total, of which 3.5 grams are fiber and two grams are starch
One slice of an apple pie - 40 grams total, of which 18 grams are sugar
One eight ounce cup of orange juice - 26 grams total, of which 21 grams are from fruit sugars
One cup of dry beans like pinto beans or navy beans - 47 grams total, of which 19 grams are fiber, 28 grams are starch

Source: USDA National Nutrient Database for Standard Reference

You can search for more carbohydrate information online for all of your favorite foods:

Nutrition Facts labels on packaged foods will also list the amount of carbohydrates per serving. It takes a little extra time and effort to look up the carbohydrate counts for all of the foods you eat, but with experience you will begin to have a good idea of approximate calorie counts and carbohydrate counts.

We will learn more about calories, carbohydrate grams, fat grams and protein grams you need later in the course when we get to the sections on calories and energy expenditure and on meal planning. However for now, you can use my calorie calculator, which will show you how many calories and carbohydrate grams you should aim for in your daily diet.

Dietary Fiber

Fiber is only found in plants, and functions sort of like a skeleton for the plants to help maintain shape and structure. Humans cannot digest fiber so it passes through the small intestine into the colon. This is good because fiber absorbs water and adds bulk to the stool, which helps to keep the colon healthy. Some disorders like diverticulitis, constipation and irregularity may be connected with not getting enough fiber in the diet.

The components of fiber include cellulose, lignin, pectin, chitan, beta-glucan and oligosaccharides and there are two general categories of fiber, insoluble and soluble.

Insoluble fiber is the type of fiber found in high fiber foods like whole grains, nuts, wheat bran and vegetables. Insoluble fiber does not dissolve in water so it helps to move material through the colon faster by increasing the bulk of the stool.

This can be very helpful to people who suffer from constipation or irregularity. Diets high in insoluble fiber may also decrease the risk of diabetes.

Soluble fiber is also found in many high fiber foods like oats, citrus fruits, apples, barley, psillium, flax seeds and beans. Soluble fiber absorbs water, which helps to soften stools making them easier to eliminate from the body. Some soluble fibers called beta glucan bind to bile acids, which contain cholesterol. A high fiber diet with this type of soluble fiber has been shown to reduce cholesterol closer to healthy levels.

Short Chain Fatty Acids

While we can’t digest fiber, some bacteria in the colon ferment some fibers. This action creates short chain fatty acids that help to regulate blood sugar levels, cholesterol, and keep the immune system healthy. We will learn more about short chain fatty acids in the Fats and oils lesson.

How Much Fiber Do You Need?

According to the Institute of Medicine:

The recommended intake for total fiber for adults 50 years and younger is set at 38 grams for men and 25 grams for women, while for men and women over 50 it is 30 and 21 grams per day, respectively, due to decreased food consumption.

People who currently have low fiber diets may want to increase their daily intake of high fiber foods slowly because some fiber may increase gas and bloating. The body adjusts the increased amount of fiber over time and the gas and bloating will decrease.

Here are some examples of high-fiber foods from the USDA National Nutrient Database for Standard Reference:

One-half cup cooked navy beans - 9.5 g
One-half cup baked beans, canned – 9 g
One-half cup cooked lentils – 7.8 g
One-half cup cooked black beans – 7.5 g
One-half cup dates – 7.1 g
One cup raisin bran cereal - 7 g
One-half cup cooked kidney beans – 6.5 g
One-half cup cooked lima beans – 6.7 g
One-half cup canned tomato paste – 5.9 g
One-half cup cooked garbanzo beans – 6.2 g
One-half cup bean with ham soup – 5.6 g
One-half cup frozen red raspberries – 5.5 g
One medium bran muffin - 5 g
One-half Asian pear – 5 g
One-half cup cooked artichoke – 4.5 g
One-half cup frozen peas, cooked – 4.4 g
One cup oatmeal – 4 g
One-half cup frozen mixed vegetables, cooked – 4 g
One-half cup raw blackberries – 3.8 g
One-half cup canned pumpkin – 3.5 g
One-half cup cooked whole-wheat spaghetti – 3.4 g
24 almonds – 3.3 g
One apple with skin – 3.3 g
One-half cup cooked barley 3 g
One cup broccoli – 2.4 g
One red sweet pepper – 2.4 g
One nectarine – 2.3 g
28 peanuts – 2.3 g
One slice whole grain bread – 2 g
15 walnut halves – 2 g

This Week’s Assignment

Well, you made it through lesson one and I have an easy assignment for you. Whole grain products such as oatmeal, whole grain breads, brown rice and whole grain pasta are very healthy sources of complex carbohydrates and fiber, plus lots of vitamins and minerals. Since many people do not get enough fiber in their diets, I would like you to concentrate on adding whole grains to your diet this week. If you really don’t eat any whole grains, add one serving of a whole grain to your diet every day. If you eat one or two servings of whole grains each day, add one more serving. It is suggested that everyone eat at least three servings of whole grain products each day.

Not sure which products are whole grain products? Look for 100 percent whole grain or 100 percent whole wheat on the label of your bread and cereal products. The Whole Grain Council has even more information on whole grains: Whole Grains A to Z

This Week's Quiz

You can test your knowledge of carbohydrates with this quiz: Quiz One - Carbohydrates

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