CHAPTER
6

Carbohydrates

In This Chapter

• What is a carbohydrate?
• The important role of carbohydrates in the body
• Distinguishing between simple and complex carbohydrates
• Identifying the best types of carbohydrates for good health
• The many benefits of soluble and insoluble fiber
• A quick review of sugar substitutes

Carbohydrates provide energy for your body, which is why the bulk of the calories in your diet should come from carbs. Every cell in your body can use the simple sugar molecule–glucose derived from carbohydrates. Without an adequate intake of carbohydrates, your nervous system, kidneys, muscles, and brain can’t function properly. It is unfortunate that many people don’t understand the critical role of carbohydrates in the body and just how important they are for a healthy body.

In this chapter, we look at the impact carbohydrates have on our diet, sort out the facts about simple and complex carbohydrates, and discuss the different types of fiber and where to find them.

Fuel for Your Body

A carbohydrate is referred to as an energy nutrient because it provides 4 calories per gram. Structurally, it’s made up of carbon, oxygen, and hydrogen molecules. Recommendations for carbohydrate requirements are based on the minimum amount required for your body to properly function. The brain needs 50 to 100 grams of carbohydrate per day. Generally your diet should contain about 45 to 65 percent carbohydrates.

Carbohydrates are classified as simple or complex. There are also sugar alcohols and sugar substitutes, which are derivatives of carbohydrates. Foods high in carbohydrates tend to get oversimplified and labeled as “good” or “bad.” This unfortunate labeling leads people to avoid them when they change their eating habits. Most people think of bread, pasta, and sugar when they think of the word “carbohydrates.” Additionally, many people don’t realize that fiber is a complex carbohydrate, too.

Carbohydrates get broken down in the body to their simplest forms, a one-sugar molecule called glucose. Glucose is the preferred source of energy for your body, brain, and red blood cells. Your body can also store glucose, but first must transform it to what is called glycogen. About a third of glycogen resides in the liver. The liver also coverts the glycogen to glucose and releases it into the blood. Muscle tissue contains glycogen stores, too, which is what gives an athlete an extra burst of energy. In fact, carbohydrates are so important to your body that when there’s an insufficient amount of carbohydrates coming from your diet to sustain your body’s needs, it’s capable of using an alternate plan for generating energy from fat called ketogenesis. There are also times when your body encounters problems utilizing energy from glucose, as happens with diabetes.

DEFINITION

Ketogenesis is the breakdown of fat due to an inadequate supply of carbohydrates. Fragments of broken fats combine to form ketone bodies, which are used instead of glucose. They can alter the body’s pH and cause dehydration, headaches, weakness, and irritability.

How Carbohydrates Are Broken Down by the Body

Carbohydrate digestion begins as soon as you place a carbohydrate-containing food into your mouth. Your salivary glands release a digestive enzyme called amylase, which helps break down a carbohydrate into smaller units of sugars. You can actually taste the action of amylase in your mouth. Simply take a small piece of white bread and hold it on your tongue. As saliva moistens the bread, you can taste it getting sweeter as it dissolves.

A carbohydrate is a combination of molecules called saccharides. A saccharide is sugar. Because food spends a short time in your mouth, only a few one-sugar molecules are released from the foods called monosaccharides. After foods are swallowed, the enzymes continue working to break apart the sugars even as they pass through your esophagus into the stomach. Amylase action ends only when the stomach acid becomes too concentrated.

In the stomach, the monosaccharides are further broken down by hydrochloric acid (HCL), which is naturally present in your stomach. Starches are also broken down, but there are no enzymes present in your stomach to break down those sugars or any fiber that may be present.

NOTABLE INSIGHT

Carbohydrates are easily digested and absorbed. Your body can digest a carbohydrate in 15 minutes to 1 hour.

As the food is released from your stomach into your small intestine in small, teaspoon-size amounts, the pancreas releases pancreatic amylase through a duct. Amylase aids in digestion of the polysaccharides and breaks them down into shorter and shorter chains of glucose and maltose. Maltase functions to break down starches into altose.

Monosaccharides like glucose are transported to the liver through your bloodstream. The liver regulates blood glucose levels and maintains it between 80 to 120 mg/DL. The liver can also store blood glucose in the form of glycogen for later use. Only enough can be stored to last for 10 to 18 hours. Galactose and fructose will also be metabolized by the liver and used by the liver for energy or to make other substances.

What is not absorbed is fiber, which moves on into the large intestine. The large intestine contains bacteria, which use the food leftovers to help produce some vitamins and also help break down and ferment fiber.

The Many Faces of Carbohydrates

There are many different types of saccharides, depending on how many saccharide units are linked together. These include mono-, di-, oligo-, and polysaccharides. The name is a clue as to how many saccharide units there are—mono- equals 1 unit, di- equals 2, oligo- equals 3 to 10, and poly- means many. The mono- and disaccharides are classified as simple carbohydrates. The oligo- and polysaccharides are classified as complex carbohydrates.

Simple Carbohydrates

The simplest forms of sugar are monosaccharides and disaccharides. The monosaccharides are glucose, fructose, and galactose, and they’re classified as simple carbohydrates. Glucose is the preferred sugar of your brain and body. Fructose is found in fruit and honey. It’s slightly sweeter than table sugar, which is sucrose. Galactose is a milk sugar.

Disaccharides are two simple sugars bonded together. These are sucrose, lactose, and maltose. Sucrose is made of glucose and fructose, and it’s the most common in our diets. Lactose is comprised of glucose and galactose, which is found in dairy products. Maltose consists of two glucose molecules.

The Glycemic Response to Carbohydrates

The glycemic index refers to a food’s ability to increase your blood glucose levels. Refined carbohydrates like white bread and fruit juice can be easily absorbed by your body. Research suggests there’s a possible relationship between consuming high-glycemic foods and obesity, as well as an increased risk of type 2 diabetes and coronary heart disease. The criticism of the glycemic load is that we don’t generally eat single food items like white bread at meals. We eat a mixed meal composed of many foods, which will alter the glycemic load.

The glycemic index is determined by the increase in blood glucose during a two-hour period after consumption of a certain amount of carbohydrates as compared to an equal amount of carbohydrates from a reference food. The higher the glycemic load, the higher the expected rise in glucose. Complex carbohydrates that are high in fiber will always have a lower glycemic index.

Sugar Alcohols

Sugar alcohols are derived from sugar found in fruits and berries. However, these sugars are chemically altered in the lab and therefore only provide 2 calories per gram. They don’t have a direct impact on blood sugar. However, because they’re a type of carbohydrate, if too much is consumed, they will eventually raise blood sugar levels.

The food industry can use sugar alcohols as thickeners or as sweeteners. Typically, they’re combined with other sugar substitutes. You can find sugar alcohols in diabetic foods, chewing gums, and hard candies. A high consumption of foods containing sugar alcohols will lead to bloating and diarrhea due to the fact that they are not completely absorbed in the digestive tract, and they will ferment, causing a laxative effect along with gas and bloating. Xylitol, mannitol, and sorbitol are all examples of sugar alcohols. Xylitol is as sweet as sugar and can be used in a 1:1 replacement. Be sure to closely read food labels, as items labeled “diabetic,” “sugar free,” or “no sugar added” may contain sugar alcohols.

Sugar Substitutes

Sugar substitutes entered the marketplace in the 1950s. Popularity has risen in response to people’s desire to decrease calories without sacrificing flavor. Because they don’t adversely impact blood sugar, sugar substitutes are popular with people with diabetes. They may be referred to as nonnutritive sweeteners, artificial sweeteners, and very low-calorie sweeteners.

The FDA regulates artificial sweeteners and has established an acceptable daily intake (ADI) for sucralose, saccharin, and acesulfame K to prevent health risks. However, you would have to consume the sweeteners in copious amounts to exceed recommendations. If you are following a healthy diet, you would automatically be consuming very little added sugars, whether they be all natural or made in a lab.

The food industry tends to blend a variety of these sweeteners to improve the overall taste profile in food products and help negate any aftertaste. Be sure to check your food labels to identify which ones you’re consuming. Check out the following list for a few of the common sugar substitutes available in the marketplace.

• Sucralose (Splenda): Made from chemically altered sugar, it passes through the GI tract undigested and unabsorbed. It’s 600 times sweeter than sugar. The product has various blends that can be used as a 1:1 replacement in baked goods and as a tabletop sweetener. It’s also used in carbonated beverages and desserts.
• Stevia (Truvia and SweetLeaf): Made from the leaves of an herb that looks similar to the mint plant. It’s 30 times sweeter than sugar and provides no calories or carbohydrates. It passes through the GI tract undigested and unabsorbed. It cannot be used in baked goods because it’s not heat stable. However, they do offer variations that can be used in baking, such as Stevia Plus.
• Agave Nectar: Made from the same plant that’s used for making tequila. It’s a refined product and has a higher concentration of fructose than table sugar. It’s 1.5 times sweeter than sugar and provides 60 calories per tablespoon as compared to sugar’s 40 calories per tablespoon. Because it’s sweeter, people find they need less of it to sweeten items, which makes it popular with diabetics. However, 1 tablespoon still has 15g of carbohydrates. It can be used as a sugar replacement in baking (⅔ cup agave to 1 cup sugar), but you must reduce the baking temperature by 25°F and reduce liquids by ¼ cup.
• Saccharin (Sweet ’N Low): Made from saccharin in the United States and sodium cyclamate in Canada. Saccharin passes through the GI tract undigested and unabsorbed. It’s 10 times sweeter than sugar by weight and provides 4 calories per gram.
• Acesulfame K (Sweet One/Sunnet): Made from acesulfame potassium, it’s 200 times sweeter than sugar and provides less than 4 calories per serving. It passes through the GI tract undigested and unabsorbed. It’s heat stable and can be used in baking.
• Aspartame (Nutrasweet/Equal): Made from aspartic acid, phenylalanine, and methanol. It’s not safe for individuals with a rare genetic disorder phenylketonuria (PKU) as they are unable to break down the phenylalanine component. It is 200 times sweeter than sugar and provides 4 calories per serving. Its sweetness lasts longer than table sugar and it has a long shelf life. It is typically combined with acesulfame K. Aspartame can not be used in baking as it breaks down in high temperatures and in high pH.

It’s a good idea to read food labels for added sugars. You may find these types of claims listed on products in the marketplace.

• Sugar-free: Less than 0.5 grams of sugar per serving.
• Reduced sugar or less sugar: At least 25 percent less sugar(s) per serving as compared to a standard serving of the traditional full-sugar food item.
• No added sugars, without added sugar, no sugar: No sugars are added during processing; contains no ingredients such as fruit juice.

FOODIE FACTOID

The suffix -ose at the end of a word denotes a sugar. The suffix -ase at the end of a word denotes an enzyme that breaks down a sugar.

Complex Carbohydrates

The complex carbohydrates are categorized as oligosaccharides or polysaccharides. Oligosaccharides contain short chains of monosaccharides linked together, such as raffinose, stachyose, verbascose, and maltodextrin.

Polysaccharides come from starch, glycogen, and fibers. Starch is the storage of glucose in plants. We use enzymes like amylase to help break down starch into smaller units of glucose. Starches are found in beans and legumes, whole grains, and vegetables. Fibers, which we will discuss next, are made up of monosaccharides. The primary source of fiber in our diets is plant cellulose.

Dietary Fiber

Dietary fiber is currently classified as soluble or insoluble. However, the Institute of Medicine (IOM) would like a third category added named functional fiber, which would include extracted fiber used as supplements. Humans are unable to digest fiber because they do not have the enzyme necessary to break it down for use in the body. Each type of fiber plays an important role in the body such as holding water, providing roughage, and reducing the risk of certain diseases. About 95 percent of fiber comes from the cell walls of plants. Most fiber is technically a nonstarch polysaccharide like cellulose, hemicelluloses, lignin, resistant starch, pectin, gums, and mucilages.

Soluble Fiber

Soluble fiber dissolves in water and forms a gel. When you cook a batch of oatmeal, you’ll note how “gummy” it becomes. Soluble fiber also slows down digestion and makes you feel full. Bacteria in the colon can ferment soluble fiber. Soluble fiber also helps maintain blood sugar levels, which is important for people with diabetes. It also helps lower cholesterol levels when the gel-like substance passes through your intestine and traps cholesterol.

Gums are found in legumes, oatmeal, and beans. Pectin is found in fruit, apples, strawberries, oranges, and citrus. Fermentable fibers are primarily pectin and gums along with a few hemicelluloses. Hemicellulose is a group of complex carbohydrates that along with pectins surround the cellulose fibers of plant cells. These fibers help increase water and sodium absorption in the colon. They can also promote cell growth, increase acidity, and provide energy by breaking down short-chain fatty acids.

NOTABLE INSIGHT

When you go on a low-carbohydrate diet, it appears that you lose a few pounds within a day. However, much of that weight is water loss. As your glycogen stores are depleted, you lose water because each glycogen molecule contains about 2.7 grams of water.

Insoluble Fiber

Insoluble fiber doesn’t dissolve in water and adds bulk to the foodstuff in your GI tract. This keeps things moving through your system by adding roughage, decreasing transit time, and making it easier for you to go to the bathroom. Bacteria in the colon don’t easily ferment insoluble fibers. Foods that contain insoluble fiber such as cellulose are whole-wheat flour, bran, cabbage, peas, beans, and grains. Hemicellulose would be found in bran, cereal, and whole grains. Lignin is found in wheat and mature vegetables, such as in the skins of potatoes.

Functional Fiber

The term “functional fiber” refers to isolated, purified forms of nondigestible carbohydrates that have beneficial effects in humans. These are made from fiber extracted from plants or animals. Common types are psyllium, inulin, and oligofructose. These can be consumed in the form of pills or powders and added to food products.

How Much Fiber Do I Need?

It has been reported that Americans only consume about 15 grams of dietary fiber daily, which is not surprising since we don’t get enough daily servings of fruits, vegetables, and whole grains in our diets. The IOM recommends 25 grams of fiber per day for women under 50 and teenage girls. Men under 50 should get 30 to 38 grams per day. Be sure to eat a combination of soluble and insoluble fiber.

FOODIE FACTOID

Functional fiber may not be vegetarian. Lobster, crab, and shrimp shells are used to create chitosan, which is an indigestible modified carbohydrate polymer sold in supplements.

Discovering High-Fiber Foods

High-fiber foods are beneficial to your health. They’re usually more nutrient-dense, will decrease your total calorie intake because you are eating fewer calories overall, and are typically lower in fat. Research has shown that diets high in fiber help maintain blood sugar levels in people with type 2 diabetes. Fiber aids in weight loss by making you feel fuller so you eat less. It can reduce heart disease risk by lowering total blood cholesterol levels. Fiber may also reduce the risk of cancer, hypertension, and gastrointestinal diseases.

Be sure to check the label when you look for fiber-rich foods at the store. The first word in an ingredient list of a fiber-rich grain should be “whole.” To be considered a good source of fiber, a product should provide 5 or more grams per serving.

Get more fiber into your diet by adding whole-fiber foods at each meal. At breakfast, start with a whole-grain cereal and add berries. For lunch, use whole-grain breads to make sandwiches or add beans as a soup or a dip. At your evening meal, make vegetables the star. Snack time also makes a great place to add finger-friendly foods like carrots or the portable apple. Check out the fiber-rich foods in the following chart. It’s easy to bulk up your diet with these fiber-rich foods.

Top 10 Fiber-Rich Foods

*All vegetables and grains are cooked.

More Is Not Always Better

Now that you realize all the great benefits fiber has to offer, you’ll want to add fiber-rich foods to your meals. It’s a good idea to gradually increase your fiber over time. If you add too much too soon, your body will not be geared up to handle it. Remember, fiber is fermented in your colon and a byproduct of fermentation is gas production (methane). If you increase fibrous foods too fast, it will cause GI distress like excess gas and bloating. Add one high-fiber food at a time and see how your body handles it. If you can tolerate the new fiber-rich food, add another the next day and so on.

FOODIE FACTOID

Epazote is a word derived from the Aztecs and means “skunk sweat.” It’s a green leafy herb with a flavor similar to anise and a smell like turpentine and citronella. It aids in the prevention of gas formation in the GI tract and is traditionally cooked with black beans.

High-Fiber Recipe

The following recipe is a great source of high fiber.

Raspberry Coconut Quinoa Breakfast Bowl

Move over oatmeal, quinoa is in the house! This sweet and savory breakfast bowl will energize you all the way to lunch.

½ cup red quinoa

½ cup white quinoa

¼ cup sweetened flaked coconut

½ cup light coconut milk, canned

1 TB. grated and peeled ginger

¼ cup packed brown sugar

⅛ tsp. kosher salt

6 ounces raspberries

2 TB fresh mint, finely minced

1. Rinse quinoa in a fine strainer.

2. Combine 2 cups of water with 1 cup of mixed quinoa in a small saucepan.

3. Bring to a boil and reduce to a simmer. Cover saucepan with lid and cook quinoa for 15 minutes or until all water has been absorbed.

4. While quinoa is cooking, toast sweetened coconut in a small nonstick saucepan for 4 to 5 minutes over medium heat, stirring occasionally until golden brown in color. Set aside.

5. Combine coconut milk, ginger, brown sugar, and salt in a small bowl and pour over cooked quinoa.

6. Fold in raspberries.

7. Garnish with toasted coconut and mint.

Variation: Use any color of quinoa.

The Least You Need to Know

• Carbohydrates are used to make glucose, which is the preferred fuel for your body.
• Complex carbohydrates contain beneficial fiber.
• Eat the skins of fruits and vegetables to up your fiber intake.
• Fiber fills you up and can aid in weight loss.
• Limit your intake of added sugars for better health.
• Read food labels when you select foods that appear to be high in fiber to ensure they actually are a good source of fiber.