IN THIS CHAPTER
Getting acquainted with carbs and their chemical structure
Sorting through the simple and complex carbs
Noting the importance of proteins and fats
Managing diabetes hinges on managing carbs. The first step is being able to identify which foods have carbohydrate. Carbohydrate is considered a macronutrient, rather than a micronutrient:
· Macronutrients: Dietary components that are required in relatively large amounts are known as macronutrients. There are three main macronutrients in the foods we eat: carbohydrate, protein, and fat.
· Micronutrients: Vitamins and minerals are essential but needed in relatively small amounts, so they are considered micronutrients.
Macronutrients are measured in grams, and most micronutrients are measured in micrograms or milligrams. To put that in perspective, there are 1,000 micrograms in one milligram, and 1,000 milligrams in one gram. Carbs are counted in grams.
Each macronutrient group is important, but for different reasons. Carbohydrates, proteins, and fats have critical roles in human nutrition:
· Carbohydrates: Carbs are the powerhouses; they provide energy in the form of glucose to the tissues, organs, and cells. Each gram of carbohydrate provides 4 calories of energy.
· Proteins: Dietary proteins are made out of amino acids, which are the very building blocks that we use to create and repair cells, tissues, and muscles.
· Fats: Fats are concentrated sources of energy and are needed to transport fat-soluble vitamins.
Most of the foods that we eat are a combination of macronutrients laced with various micronutrients. For example, meats contain both protein and fat. Legumes have both protein and carb. Even grains and vegetables have a little protein along with the carbs. This chapter identifies the key members in the family of carbohydrates and discusses the role of the noncarb counterparts.
Looking at the Chemical Structure of Carbohydrates
All carbohydrates have something in common: They are built out of sugar molecules. Sugar molecules can exist separately as single units, or they can join together in pairs to form double sugars. The scientific term for a single sugar is monosaccharide. The double-sugar units are known as disaccharides. Many sugar molecules can join together in long chains, and those are called polysaccharides. Starch and fiber are examples of polysaccharides.
Monosaccharides (single sugars) and disaccharides (double sugars) are also known as simple carbohydrates. Polysaccharides (many sugars linked together) are referred to as complex carbohydrates. See Figure 3-1 for a closer look at the chemical structure of carbohydrates. Note that both starch and fiber are considered polysaccharides (complex carbohydrates) made out of chains of glucose molecules. The key difference is that starches are digestible and fiber is not. Digestive enzymes in the intestine easily cut the bonds that link the glucose molecules in starch. The enzymes can’t cut through the stronger bonds that link the glucose chains in fiber.
© John Wiley & Sons, Inc.
FIGURE 3-1: Carbohydrate chemical structure.
A common question I hear is “If carbs digest and turn into glucose, why not skip the carbs and just eat proteins and fats?” The flaw with that approach is that we need the nutrients found in healthy carb foods. Health experts warn against overconsumption of artery-clogging saturated fats. Plant foods are naturally low in saturated fat, while animal foods (such as meats, cheese, and butter) often have significant amounts of saturated fat, depending on which cuts of meat you choose. Plant foods such as whole grains, fruits, and vegetables offer fiber, while meat, cheese, eggs, and fat do not have any fiber. Every food group offers health benefits if you choose foods wisely. The best diets provide a variety of nutritious foods, from all food groups, as long as they’re consumed in appropriate serving sizes.
Not all carbs are created equal when it comes to good nutrition, though. Whole grains, legumes, fruits, and vegetables are filled with the nutrients we need for health. Refined grains, desserts, sodas, and the seemingly endless supply of junk foods don’t offer much in terms of healthy nutrition. Unhealthy food choices dump in carbs and calories and do more harm than good. Healthy, natural carbohydrate-containing food groups provide a diverse array of critical nutrients:
· Whole grains provide fiber, B vitamins, magnesium, phosphorus, manganese, iron, and vitamin E.
· Fruits and vegetables contribute fiber and are rich in vitamin A, vitamin C, potassium, folic acid, bioflavonoids, and antioxidants, just to name a few.
· Milk and yogurt provide protein, calcium, vitamin D, vitamin B12, phosphorus, and more.
· Legumes are not only high in fiber, but they also pack in the protein and offer several B vitamins, as well as magnesium, zinc, and iron.
We simply must have glucose traveling through our bloodstream at all times. Glucose is the preferred fuel for the brain, the central nervous system, and red blood cells. Glucose also provides fuel to muscles. You can also burn fat for energy, but you need to burn glucose and fat in the proper fuel mix to keep metabolism on an even keel. An appropriate amount of carb is needed to properly fuel your body. You can’t drive a car without fuel, and you can’t operate a human body without glucose in your bloodstream. (I realize we have electric cars now, but we don’t have electric bodies, so I stand by my statement!) To find out just how much carb you need, see Chapter 5 . For more information on how glucose is utilized as fuel for the human body, see Chapter 4 .
Introducing the So-Called Simple Carbohydrates
The monosaccharides and disaccharides illustrated in Figure 3-1 are considered simple carbohydrates (sugars). There are naturally occurring sugars in many foods. Fruits, milk, and yogurt are examples of foods that contain natural sugars.
Take a closer look at the carbohydrate building blocks, the single sugars. Sugar molecules are made out of carbon, hydrogen, and oxygen, which can be assembled to form glucose, fructose, or galactose. Those are the three monosaccharide single sugars. The single sugars can decide to partner up with each other, form a loving bond, and become disaccharides. See Figure 3-2 to meet the happy couples. The following sections go into more detail on all the simple carbohydrates.
© John Wiley & Sons, Inc.
FIGURE 3-2: The sugars.
Going au naturel with glucose, fructose, and lactose
All fruits have natural sugar. Fruits contain both glucose and fructose. In fact, fruit is 100 percent sugar. There’s no protein or fat in fruit. Avocados and tomatoes are considered fruits if you ask a botanist. However, when considering the actual composition of those foods in terms of calories, carbs, and the effect on blood sugar, tomatoes get shipped off to the “vegetable” group and avocados are relegated to the “fat” group because they are more similar in composition to the items in those respective food groups. Vegetables also contain glucose and fructose, but in lower amounts than fruit.
While fructose is a natural sugar, high-fructose corn syrup is not. The latter is made in mass quantities and added to foods during manufacturing. Fruit has positive nutritional benefits and is part of a balanced diet. High-fructose corn syrup does not offer any nutritional benefits. For more information about sugars and various alternative sweeteners, see Chapter 12 .
Lactose is the natural sugar in milk. It is a disaccharide, or double sugar. Lactose is digested in the intestine as lactase enzymes clip apart the double sugar into its two single sugars, glucose and galactose (refer to Figure 3-2 ). Only single units of sugar are absorbed into the bloodstream.
Some people do not have enough of the enzyme to properly break down lactose. If you are unable to digest milk, then you are likely lactose intolerant. People who are lactose intolerant feel gassy and bloated or crampy (or have diarrhea) after consuming milk (and sometimes other dairy products). One solution is to buy lactose-free milk. Lactose-free milk has the enzyme pre-added to the milk. The double sugar, lactose, breaks down into the individual sugars, glucose and galactose, before you even drink it. The carton will say 100 percent lactose-free milk, but keep in mind the actual amount of sugar is exactly the same as normal milk — it just contains single sugars instead of the double sugar. Another work-around on lactose intolerance is to use a nondairy milk substitute. For more tips, see Chapter 11 .
If you are lactose intolerant, you may still be able to tolerate cheese. That’s because cheese is basically carbohydrate-free. Cheese is made from the protein and the fat from milk, but it has no (or only trace amounts of) lactose. Some people who are lactose intolerant seem to tolerate yogurt fairly well too. The lactase enzyme needed to digest lactose sugar is also available in tablets and liquid drops, so you can take it as needed when you have a serving of dairy.
Finding other forms of sugar: Sucrose, maltose, honey, and syrups
Sucrose is the fancy name for white sugar. It is a disaccharide (double sugar) that is made from glucose paired with fructose (refer to Figure 3-2 ). When you digest it, which occurs in the intestine, the two sugars break apart and are individually absorbed into the bloodstream.
Maltose consists of two glucose molecules joined together (refer to Figure 3-2 ). Maltose results when starches are being broken down into sugars. The maltose can quickly split into individual glucose sugars. Maltose and malted grains are used for making alcoholic beverages. Maltose and other sugars can be converted to alcohol by yeast during the fermentation process.
Honey is composed of fructose, glucose, several oligosaccharides, and water. Oligosaccharides are chains of three to nine monosaccharide sugars, whereas polysaccharides have ten or more sugar molecules in the chain. The bees add enzymes to the honey when they produce it, so most of the sugars exist in monosaccharide form. Honey is slightly sweeter tasting than sugar, so you may achieve the same sweetness when using a smaller portion.
Syrups may be of the naturally occurring variety, such as pure maple syrup. Many other types of syrups are manufactured, often out of high-fructose corn syrup. Maple syrup is high in natural sucrose but also has traces of fructose and glucose.
Spotting simple carbs in the grocery aisles
When looking at Nutrition Facts food labels, the grams of sugar are indented and listed under the total carbohydrates. All the sugars discussed thus far in this chapter are lumped together and called “sugar.” That means the natural sugars in fruit and milk get counted as sugar on the food label. It’s more informative when carb counting to look at the total grams of carbohydrate on Nutrition Facts labels. The sugars are already included in the total carbs. If you’ve been looking only at the grams of sugar, you’ve been missing the big picture. The starches eventually break down into simple sugars during digestion, so keep your eye on the total carbohydrate counts. For more information on label reading, see Chapter 7 .
Look to the perimeter once you’re inside the supermarket, as that is where you typically find the healthy foods that contain natural sugars. Fresh fruits and vegetables and reduced-fat dairy products such as milk and yogurt are considered to be part of a well-balanced and healthy diet. Those are real foods with real nutrition. Fruits, vegetables, and reduced-fat dairy products contain important vitamins and minerals and offer health benefits.
On the other hand, many not-so-healthy foods are loaded with added sugars in the form of sweets and treats, such as cookies, pastries, ice creams, and candy. Use caution when steering your grocery cart down those aisles. Excessive intake of desserts can end up piling on the carbs and the calories. Use caution at the checkout stand too, as the store is making one last attempt to sell you candy.
Checking Out the Complex Carbohydrates
Complex carbs are made out of many glucose molecules linked together. Starch and fiber (refer to Figure 3-1 ) are both considered complex carbohydrates. Starches digest and eventually break down into individual glucose molecules. Fiber, on the other hand, does not turn into glucose. Fiber is the nondigestible part of whole grains and other plant foods. The following sections give you the full scoop on complex carbs.
Identifying the starches
Grains, breads, bagels, tortillas, cereals, oats, grits, rice, quinoa, barley, farro, millet, bulgur, and pasta are all examples of complex carbs. When counting carbs, foods are grouped according to the amount of carbohydrate they contain. Some vegetables have carb counts similar to grains and breads, so those particular vegetables are lumped together in the “starch” group. Examples of starchy vegetables include potatoes, corn, hominy, parsnips, peas, yams, yucca, pumpkin, and the family of legumes. Legumes include the split pea and dried bean family, pinto beans, black beans, kidney beans, lentils, red beans, navy beans, and garbanzo beans (also known as chickpeas). For a more complete list of starches, see Appendix A .
Focusing on fiber
Fiber is found only in plant foods. You find fiber in whole grains, legumes, nuts, fruits, and vegetables. Refined grains, such as white bread and white rice, are stripped of their natural fibers during processing.
Fiber is made out of glucose molecules, so it fits the definition of a carbohydrate. The glucose molecules are all linked together tightly in long chains. The bonds that hold the glucose molecules together are strong, and our digestive enzymes are unable to cleave them apart. Fiber is not digested or absorbed, so when counting grams of carbohydrate, fiber grams can be subtracted from the total grams of carbohydrate. For more tips on identifying total carbohydrate and fiber counts on packaged foods, see Chapter 7 .
In the following sections, I describe the health benefits and types of fiber, and I explain how to set your fiber intake goal.
Highlighting fiber’s health benefits
Fiber has numerous health benefits. For example:
· Fiber is vitally important to the digestive system. Fiber keeps the food moving through the intestinal tract. In so doing, fiber promotes intestinal health.
· Fiber, the soluble variety, is heart-healthy because it helps reduce blood cholesterol levels. See Chapter 16 for more details.
A whole grain has three main components: the bran, the endosperm, and the germ. The bran is the fiber-rich outer layer. The inner part of the grain contains the endosperm and the germ. The endosperm is the starchy part but also contains some protein. The germ is the actual seed for a new plant, and it contains vitamins, minerals, and healthy oils. Refining grains removes the bran and the germ. Many nutrients are lost in the refining process, so grains are often fortified. Fortification is an attempt to put back some of the vitamins that were removed by refining, but the fiber is not replaced.
Giving a nod to the two fibers: Soluble and insoluble
There are two main types of fiber: soluble (absorbs water) and insoluble (does not absorb water). Both types of fiber have health-promoting qualities. Soluble fiber is heart healthy because it can naturally help to lower your blood cholesterol levels. Insoluble fiber can improve intestinal health. Many plant foods contain both types of fiber. For example, legumes are high in both soluble and insoluble fiber.
Soluble fiber absorbs water and swells. Oatmeal has soluble fiber, and when you add water and cook it, the grain swells and gets sticky. The dried-bean family is also rich in soluble fiber. For a more in-depth discussion on how soluble fiber performs its cholesterol-lowering feat, see Chapter 16 . That’s also where you find a more complete list of foods that contain soluble fiber.
Insoluble fiber does not absorb water. You could sprinkle bran into a glass of water and it would float on top all day. As insoluble fiber moves through the intestinal tract, it pushes the food through and helps prevent constipation. Insoluble fiber gently rubs the intestinal walls as it moves past, and that helps keep the intestine and colon healthy. Fiber in the diet may reduce the risk of developing hemorrhoids and diverticular disease. Foods that contain insoluble fiber include whole grains, legumes, nuts, seeds, fruits, and vegetables. The skins of fruits and vegetables are particularly high in insoluble fiber.
When it comes to having diabetes, a diet higher in fiber offers additional benefits. Refined grains such as white rice and white bread digest quickly, which can cause higher post-meal blood-glucose spikes (which are not good). Whole grains and legumes take more time to digest, so the glucose from the meal enters the bloodstream gradually and the blood-glucose level may not peak as sharply (which is good). Additionally, since a meal with more fiber takes longer to digest, you may feel satisfied for a longer period of time. That could reduce between-meal snacking and help with weight control.
Setting your personal fiber intake goal
The National Academies of Sciences, Engineering, and Medicine provide Dietary Reference Intake guidelines for nutrients including fiber. Their suggested intake targets for fiber are in Table 3-1 .
TABLE 3-1 Daily Fiber Recommendations for Adults
|
Gender |
Ages 19 to 50 |
Ages 51 and Older |
|
Women |
25 grams |
21 grams |
|
Men |
38 grams |
30 grams |
If your diet is typically low in fiber, it is best to increase your intake gradually over a period of a few weeks to give your body a chance to adjust. Increasing fiber intake too rapidly could lead to gassiness and bloating. Be sure to drink plenty of water too. Fiber keeps things moving along, but only if you stay well hydrated.
If you have a diabetes complication known as gastroparesis, you should not be eating much fiber at all. Gastroparesis is a type of neuropathy that affects the intestinal tract. The nerves that stimulate peristalsis no longer function properly; therefore, foods end up transiting very slowly and unpredictably, which makes it difficult to predict blood-glucose levels and insulin dosing. Gastroparesis can lead to nausea, vomiting, and constipation. The diet recommended for gastroparesis is a low-fat and low-fiber diet, with smaller, more frequent meals. Those recommended dietary modifications help foods digest more quickly and predictably. Given the complexities of the condition and treatment, seek advice from your healthcare provider and discuss nutritional interventions with a registered dietitian.
Spotting complex carbs in the grocery aisles
Try the following tips as you shop for complex carbs at the grocery store:
· The produce section offers complex carbs in potatoes, yams, sweet potatoes, yucca, corn, peas, and an array of winter squashes (butternut, acorn, Hubbard, and pumpkin, to name a few.)
· In the canned-food section or the dried-goods section, you can choose from any of the dried beans, split peas, and lentils.
· As you head down the cereal aisle, look for whole-grain breakfast cereals with little or no added sugars.
· As for snacks, choose whole-grain crackers and pretzels, or popcorn (opt for microwave lite or pop your own to control the fat).
· Look for the words “whole grain” or “whole wheat” when picking breads, bagels, or tortillas. There are even pastas that are made with whole grains. Seek out whole grains to cook and serve with lunches and dinners. Skip the boxes of flavored (usually high sodium) rice mixes and try unprocessed whole grains such as brown rice, quinoa, farro, teff, millet, amaranth, barley, and bulgur. They are all easy to prepare.
For more information on identifying whole-grain products in packaged foods, see Chapter 7 .
Recognizing Carb-Free Counterparts
Many foods do not contain any carbohydrate, as you find out in this section. Protein and fat are the two macronutrients that don’t directly raise blood-sugar levels because they are not made out of glucose molecules:
· Proteins are made out of building blocks called amino acids. The body uses dietary proteins to obtain the amino-acid building blocks needed to create and repair its tissues, cells, organs, and muscles.
· Fats are made from fatty acids. Dietary fats add flavor and also help transport fat-soluble vitamins. A certain amount of dietary fat is essential, but that budget is easily met, and often exceeded, so it pays to be mindful about how much fat is being consumed. It’s also important to choose the heart-healthier fats.
Pumping up with proteins: Meat, fish, and other sources
If it once flew, swam, or roamed the earth and now it’s on your dinner plate, then it’s a protein food and does not contain carbs. It pays to choose lean meats, because meat fats tend to be saturated, and that kind of fat is not healthy for your blood vessels (as I explain later in this chapter). Look for meats that are not marbled. Take the skin off poultry before eating. Fish, on the other hand, contains one of the heart-healthiest kinds of fat: omega-3 fatty acids.
Other carb-free protein sources include eggs and cheese. Egg whites contain quality protein, and egg yolks contains cholesterol and fat. (Chapter 16 brings you up to date on the cholesterol debate; current recommendations may surprise you.) Cheese doesn’t have carbs even though it is made from milk. To make cheese, enzymes are added to whole milk. The enzymes cause the protein and the fat from the milk to come together and form a solid curd. The liquid that remains behind contains the carb. Cottage cheese is mostly protein and is very low in carb because not that much liquid is retained in packaging the cottage cheese.
Vegetarian meat replacements vary, but most are low- or no-carb. Check labels on vegetarian hot dogs, burgers, or other faux meats for the product’s nutrition information, and check out Chapter 7 if you need help with reading labels.
Finding the healthiest fats and oils
Fats and oils do not contain carbohydrate. They add flavor to foods and come in many forms. Some fats are solid at room temperature, such as butter, while others are liquid at room temperature, such as oil. Some fats come from animals, which include the fats found in meats and dairy products. Other fats come from vegetable sources, such as nuts, oils, and avocados. All fats are calorically dense. For example, a single tablespoon of oil has about 135 calories, and ¼ cup of nuts is close to 200 calories. It pays to pick your dietary fats wisely and to savor them in reasonable portions.
Sampling the good stuff: Unsaturated fats
The heart-healthiest fats are unsaturated. Unsaturated oils tend to be liquid at room temperature. Two types of unsaturated fats exist:
· Monounsaturated fats are some of the best when it comes to heart health. They are found in olive oil, canola oil, peanut oil, avocados, and nuts.
· Polyunsaturated fats are found in many oils, including corn, cottonseed, flaxseed, grape seed, safflower, sesame, soybean, and sunflower oils. Mayonnaise and margarine also contain polyunsaturated fats.
Unsaturated fats should be enjoyed in reasonable portion sizes. See Chapter 16 for more on choosing fats wisely and zeroing in on the Nutrition Facts food label sections related to fat and heart health.
Trimming your intake of saturated fats
Saturated fats are linked to blood-vessel diseases such as heart disease. Saturated fats can increase LDL cholesterol levels. LDL is the artery-clogging, bad kind of cholesterol. Saturated fats are more likely to be solid at room temperature. Examples include marbled meats, bacon, lard, and full-fat dairy products including butter, cream cheese, sour cream, cream, and whipped cream.
To trim back on saturated fats, choose nonfat or reduced-fat dairy products, pick lean meats, and use smaller amounts of butter. Replace saturated fats with unsaturated fats when possible, such as sautéing in olive oil instead of butter.
Steering clear of trans fats
Trans fats are public enemy number one, if you ask heart-health experts. Eating trans fats increases your risk of developing heart disease and stroke. They raise LDL cholesterol levels (the artery-clogging, bad kind) just like saturated fats do. However, trans fats hit you with a double whammy because they also lower your HDL cholesterol (the artery-cleaning, good kind).
Animal products contain traces of naturally occurring trans fats, but the vast majority of dietary trans fats are formed during a food manufacturing process known as hydrogenation. When hydrogen atoms are forced into liquid vegetable oils, the chemical structure of the oil changes and the oils begin to solidify. Hydrogenated oils are solid or semi-solid at room temperature. The word “trans” refers to the orientation of the hydrogen atoms as they bond to the carbon atoms in the fatty acid.
Hydrogenated fats have a long shelf life. Restaurants, especially the fast-food industry, use hydrogenated fat in the fryer because it can be used over and over again before changing the oil. You can minimize your intake of trans fats by avoiding fried foods when dining out.
Vegetable shortening is another source of trans fat. Beware; many baked goods are made with shortening, so limit commercially produced pastries and baked goods. Your best-bet margarines are the liquid or tub varieties instead of the stick versions.
Food labels are allowed to say 0 grams of trans fat as long as there is less than 0.5 grams of trans fat per serving. If you eat multiple servings, they potentially could add up to a significant amount of trans fat. That’s why you should read ingredients lists and simply avoid products with hydrogenated or partially hydrogenated oils. For packaged foods, read the Nutrition Facts food labels and look for “0 g trans fat.” Read the ingredients list too and make sure there are no hydrogenated or partially hydrogenated oils listed. See Chapter 7 for more info on reading food labels.
Exploring the role of noncarb foods in diabetes management
Protein foods and heart-healthy fats and oils provide key nutrients, and they also add variety and pleasure to eating. For tips on choosing foods wisely as you manage diabetes, see Chapter 13 ; the following sections give you an introduction.
Satisfying your appetite
Have you ever had a light lunch, such as fruit and nonfat yogurt, and then been hungry again in an hour? Or have you been uncomfortably stuffed for several hours after a heavy, high-fat meal? A balanced, mixed meal takes roughly four hours to fully digest. Mixed meal refers to a meal that has a balanced amount of carbohydrate, protein, and fat. Fat tends to delay digestion, and it increases satiety (gratification and satisfaction). Even lean proteins have some fat, so no need to go out of your way to add too much fat. People generally feel satisfied for a longer period of time if they eat balanced meals.
The plate model is a good tool for striking the right balance in meal planning. Chapter 8 provides more information about using the plate model. To get some ideas on meal planning, check out the sample menu plans for breakfast, lunch, and dinner ideas in Chapters 19 , 20 , and 21 .
Smoothing out your numbers
When carb foods digest too rapidly, the glucose from the meal ends up in the bloodstream very quickly. For example, fruit juice or sugary beverages take only about 15 minutes to get digested and absorbed. The rapid rush of glucose into the bloodstream can wreak havoc with blood-glucose control efforts. To minimize blood-glucose spikes, it makes sense to limit liquid concentrated carbs. (For more info on the pitfalls of sugary beverages, see Chapter 11 .) Beyond that, careful meal planning can help to minimize blood-glucose variability.
Choose foods wisely and control portion sizes. Strike a balance between carbs, proteins, and fats. Pick lean proteins and aim for a portion about the size of the palm of your hand. Choose higher-fiber grains and keep the portion to about the size of your fist. For more information on the mealtime variables that influence post-meal blood-glucose levels, see Chapter 10 .