8 Carbohdyrates


  • The chemical structure and function of  carbohydrates
  • Foods rich in carbohydrates
  • How the two types of fiber support your health
  • How your body uses sugar and sugar alternatives
  • Diseases related to carbohydrate disorders

Carbohydrate Overview & Structure

Carbohydrates are the perfect nutrient to meet your body’s nutritional needs. They nourish your brain and nervous system, provide energy to all of your cells (and within proper caloric limits), and help keep your body fit and lean. Specifically, digestible carbohydrates provide bulk in foods, vitamins, and minerals, while indigestible carbohydrates provide a good amount of fiber with a host of other health benefits. Like fruit, vegetables, and whole grains, the plants we eat synthesize the fast-releasing carbohydrate, glucose, from carbon dioxide in the air and water and by harnessing the sun’s energy. Plants convert the energy in sunlight to chemical energy in the molecule glucose. Plants use glucose to make other larger, more slow-releasing carbohydrates. When we eat plants, we harvest the energy of glucose to support life.

Carbohydrates are organic compounds containing a ratio of one carbon atom to two hydrogen atoms to one oxygen atom. Basically, they are hydrated carbons. The word “carbo” means carbon, and “hydrate” means water. Glucose is the more abundant carbohydrate in the human body.

Watch the video about carbohydrates and sugars

Carbohydrates: Two Very Different Types

There are two types of carbohydrates based on how quickly they break down in the body, either fast or slow:
Fast-releasing carbohydrates are sugars. Simple sugars break down very quickly, flooding your body with quick energy.

Slow-releasing carbohydrates are starches and fibers.
Starch molecules are found in abundance in grains, legumes, and root vegetables, such as potatoes. Eating raw foods containing starches provides very little energy as the digestive system has a hard time breaking them down. Cooking breaks down the crystal structure of starches, making them much easier to break down in the human body, providing energy.
Fiber provides something different from the body: humans lack the enzymes to break down fiber, but the bacteria in our gut biome can provide some assistance. These bacteria break down some of the fiber, but most of the fiber we consume functions to make us feel full (help us regulate our appetite) and help clean out the intestinal tract. Think of fiber as a broom that sweeps out the insides of your intestinal tract.

Functions of Carbohydrates

The four primary functions of carbohydrates in the body are:
1) To provide energy – The simplest carbohydrate, and the one most abundant in the body, is glucose. For all organisms, from bacteria to plants to animals, glucose is the preferred fuel source. The brain is completely dependent on glucose as its energy source (except during extreme starvation conditions). Many other more complex carbohydrates break down and become glucose in the body.
2) Store energy – Extra carbohydrates are stored in our liver and muscles, ready for the body to use if necessary; it’s like having a backup battery.
3) Build macromolecules – Although most absorbed glucose is used to make energy, some glucose is converted to ribose and deoxyribose, which are essential building blocks of important macromolecules, such as RNA, DNA, and ATP. Glucose is additionally utilized to make the molecule NADPH, which is important for protection against oxidative stress and is used in many other chemical reactions in the body. If all of the energy, glycogen-storing capacity, and building needs of the body are met, excess glucose can make fat.
4)  Spare protein and fat for other uses – When the body needs glucose and doesn’t have any, the body will scavenge proteins (your muscles) and convert them into glucose. Adequate glucose in the body spares the breakdown of proteins from being used to make glucose needed by the body.

What Foods are Rich in Carbohydrates?

Carbohydrates are contained in all five food groups: grains, fruits, vegetables, meats, beans (only in some processed meats and beans), and dairy products. Fast-releasing carbohydrates are more prevalent in fruits, fruit juices, and dairy products, while slow-releasing carbohydrates are more plentiful in starchy vegetables, beans, and whole grains. Fast-releasing carbohydrates are also found in large amounts in processed foods, soft drinks, and sweets. On average, a serving of fruits, whole grains, or starches contains 15 grams of carbohydrates.
In choosing dietary sources of carbohydrates, the best ones are those that are nutrient-dense, meaning they contain more essential nutrients per calorie of energy. In general, nutrient-dense carbohydrates are minimally processed and include whole-grain bread and cereals, low-fat dairy products, fruits, vegetables, and beans. In contrast, empty-calorie carbohydrate foods are highly processed and often contain added sugars and fats. Soft drinks, cakes, cookies, and candy are examples of empty-calorie carbohydrates. When you choose nutrient-dense food, you give your body better nutrition and more opportunities to function optimally. We all want to live our best life, feel our best, chose our food wisely.

The Argument for Eating Fiber

Adult females need 25 grams of fiber per day and males need 38 grams for good health, but most Americans get only about 15 grams a day. The Dietary Guidelines Advisory Committee states that there is enough scientific evidence to support that diets high in fiber reduce the risk of obesity and diabetes, which are primary risk factors for cardiovascular disease. Dietary fibers are very beneficial to our health. Fiber is found in peas, beans, oats, barley, rye, whole-grain foods, flax, cauliflower, and avocados. Cellulose is the most abundant fiber in plants, making up the cell walls and providing structure.

Whole Grains & Health

Bread Basket

Whole grains are vital to a healthy diet. In addition to fiber, whole grains offer other slow-releasing carbohydrates, antioxidants, vitamins, and minerals, all of which are needed for good health.   But unfortunately, most people consume diets heavy in enriched flour, even though this has been proven to damage our health. Why would we eat white flour when whole grains are so much healthier for us?  Good question!  Let’s learn about grains, the history of flour to catch you up on why we eat what we eat.

What is Whole Grain?

A grain is the seed of a plant.  A whole-grain refers to eating the entire seed, not just the white insides (endosperm), but also the hard exterior layers (bran and germ).  Many countries grow and eat wheat (a grain), but many other grains can make flour, such as rye,  rice, and spelling.

Watch the video on the health benefits of whole grains

For more information on Whole Grains, check out the link to Whole Grains 101 below.



How We Ended Up With White Flour

If you swallow a grain whole, it will travel through your body without being broken down, and therefore you aren’t getting any energy or nutrition from the grain.  To make the grain into food, humans discovered they had to crack it open before eating it.  In ancient times whole grains were cracked open using quern stones that required hours of hand labor, as in the photo to the right.

As technology slowly advanced, the quern stone was modified into the millstone. The process of milling breaks the hard outer bran coat of the wheat seeds. The bran and germ, which contain the most fiber, vitamins, and minerals, are removed by sifting. In America, Oliver Evans built the first flour mill, which was powered by a watermill. It used a series of elevators that moved grain through the mill, cleaning it first, then grinding and sifting it. Today, the vast majority of flour milled and used in foods and cooking in America is white flour. The modern milling process of preparing white flour removes between 50 and 85 percent of B vitamins, vitamin E, calcium, iron, potassium, chromium, phosphorus, zinc, magnesium, manganese, and cobalt.  We developed an industry where we could take tons of grain and crack them open to make the nutrition accessible to the body; HOWEVER, we REMOVED most of the nutrition in making flour.  Surprise, surprise, when you remove nutrition from one of the most common items eaten, people end up with vitamin and mineral deficiencies such as pellagra (niacin, B3), beriberi (thiamine, B1), and anemia (iron) plagued. One of the first public health campaigns to improve Americans’ health was to make flour nutritious again.  Instead of rethinking the process of milling, we decided to enrich the flour.  Enrichment means adding to; we added back in the B vitamins, niacin, thiamine, riboflavin, and folate,  along with iron, to combat dietary deficiencies.  Enriching white flour has been a successful strategy to improve public health. However, enriched flour contains only 6 percent or less of the recommended daily intake of the vitamins and minerals it “replaces.” Overwhelming scientific evidence now shows that diets containing high amounts of whole grains rather than refined white flour decrease weight gain and the risk for many chronic diseases, including certain types of cancer and diabetes. Whole grains contain a whole nutrient package that is not replaced by enriched flour.

More Reasons to Eat Whole Grains

Whole grains contain more starches and fiber, so they are more satisfying. Additionally, once in the stomach, whole-grain foods take longer to digest.  This increased digestive time in your stomach means that you literally feel (and are!) full longer. Remember, too, that they contain fiber, which makes elimination much smoother. Whole-grain foods satisfy the body the entire way through the digestive tract and provide the nutrients that also better satisfy the body’s functional needs. The 2015 Dietary Guidelines recommend that half of all grains in your diet come from whole grains, as you recall from a previous chapter. What percentage of your diet is a whole grain?  Next time you are buying foods, look at the labels closely, and see if you can incorporate some whole grain options to improve your health and decrease disease risk.

How to Find Whole Grains

Consumers are becoming more aware of the many health benefits of whole grains and are starting to look for whole grains in the foods they buy.  The food industry wants to capitalize on this interest without improving their products, so they use words on the packaging that leads you to think you are getting whole grains, but you are not.  For example, ‘whole wheat’ does not mean the product is made from 100% whole grains.  In fact, brown bread isn’t necessarily better for you than white bread:  some manufacturers add caramel coloring to the bread dough, not whole grains (which contribute a darker color).  The Food and Drug Administration (FDA) now mandates that the food industry label whole-grain foods as made from 100% whole grains.  Anything else, it’s not whole grains (and you won’t’ reap the health benefits of whole grains).  This means that if you look at an ingredient label, it must say 100% whole-grain or 100% whole-wheat flour as the first ingredient and not contain wheat flour, white flour, yellow corn semolina flour, degerminated flour, or durum flour.  In America, whole-grain choices are improving, but progress still needs to be made on reducing the added sugar content of many industrially prepared bread, assuring added fiber comes from good sources, eliminating ambiguous labels and claims on packaging, and reducing the costs of whole-grain bread, which still exceed that of white bread.

Sugar and Sugar Alternatives

Sweetness is one of the five basic taste sensations of foods and beverages and is sensed by taste buds on your tongue. Many carbohydrates are sugars and taste sweet. However, not all carbohydrates are equally sweet. Some carbohydrates break down really quickly; these are called fast-releasing carbohydrates, and they taste the sweetest. That said, your tongue is so sensitive that even meager amounts of slow-releasing carbohydrates can be detected and will stimulate the sweetness taste sensation. Sweetness varies between the different carbohydrate types—some are much sweeter than others.
Due to the potential health consequences of consuming too many added sugars, sugar substitutes have replaced them in many foods and beverages. Sugar substitutes may be from natural sources or artificially made. Those that are artificially made are called artificial sweeteners and must be approved by the FDA for use in foods and beverages. The artificial sweeteners approved by the FDA are saccharin, aspartame, acesulfame potassium, neotame, and sucralose. Stevia is an example of a naturally-derived sugar substitute. Consuming foods and beverages containing sugar substitutes may benefit health by reducing the consumption of simple sugars, which are higher in calories, cause tooth decay, and are potentially linked to chronic disease. However, the most common side effect of consuming sugar substitute products is gastrointestinal upset due to their incomplete digestion.

Understanding Carbohydrates from Product Information

While nutrition facts labels can help you figure out how many carbohydrates to eat (the whole package? half?), these same labels do not help in determining whether a food is refined or not. The ingredients list does provide some help. It lists all the food’s ingredients in order of weight. The first ingredient is the one that is most present in the food. When choosing between two pieces of bread, pick the one that lists whole wheat (not wheat flour) as the first ingredient, and avoid those with other flour ingredients, such as white flour, enriched flour, or cornflour. Eat less of products that list high fructose corn syrup and other sugars such as sucrose, honey, dextrose, and cane sugar in the first five ingredients. If you want to eat less processed foods, then in general, stay away from products with long ingredient lists.
On the front of food and beverages, the manufacturers may include claims such as “sugar-free,” “reduced sugar,” “high fiber,” etc… The Nutrition and Labeling Act of 1990 has defined the food industry and consumers what these labels mean, so there is a standardized definition. See the table below.

Food Label Claims

Label Definition
Sugar-free Contains less than 0.5 grams of sugar per serving
Reduced sugar It contains 25 percent less sugar than a similar product.
Less sugar It contained 25 percent less sugar than a similar product and was not altered by processing.
No sugars added No sugars added during processing.
High fiber Contains at least 20 percent of the daily value of fiber in each serving
A good source of Fiber It contains between 10 and 19 percent of the daily value of fiber per serving.
More fiber Contains 10 percent or more of the daily value of fiber per serving

Source: US Food and Drug Administration. “Appendix A: Definitions of Nutrient Claims.” Guidance for Industry: A Food Labeling Guide.

Diseases Related to Carbohydrates

Consumption of too much sugar can lead to Oral Disease, which includes decay of the teeth, gums, and mouth tissues.
To avoid or reduce oral disease, switch to a non-sugar drink, and brush your teeth. Overconsumption of sugar does not cause diabetes. With diabetes, just like other diseases, genetics, nutrition, environment, and lifestyle factors are all involved in determining a person’s risk of developing diabetes. There are two types of diabetes. Type 1 Diabetes was once a death sentence but can now be treated with insulin injections. However, insulin injections do not cure the disease, and people with diabetes can suffer many disease complications. Diabetes complications can be relieved by strictly managing blood-glucose levels, adhering to a healthy diet, and increasing physical activity. The incidence of Type 2 Diabetes has more than doubled in America in the past thirty years, and the rise is partly attributed to the increase in obesity. The front-line approach for treating Type 2 Diabetes includes eating a healthy diet and increasing physical activity. The long-term health consequences of diabetes are severe. They result from chronically high glucose concentrations in the blood and other metabolic abnormalities such as high blood lipid levels.

What Is Diabetes?

Diabetes is a disease of insulin deficiency (the body doesn’t make enough insulin, which is essential in moving glucose out of the bloodstream and into cells for use) and glucose over-sufficiency. Diabetes is a metabolic disease and is one of the top three diseases in America. It affects millions of people and causes tens of thousands of deaths each year. Like other diseases, genetics, nutrition, environment, and lifestyle are all involved in determining a person’s risk of developing diabetes. One sure way to decrease your chances of getting diabetes is to maintain optimal body weight by consuming a balanced diet balanced in carbohydrate, fat, and protein intake. There are three types of diabetes: Type 1 diabetes, Type 2 diabetes, and gestational diabetes. According to the Center for Disease Control (CDC), 34.2 million Americans—just over 1 in 10—have diabetes. 88 million American adults—approximately 1 in 3—have prediabetes.

Are You at Risk for Prediabetes?

Follow the link to the short survey.


Type 1 Diabetes

Type 1 diabetes is a metabolic disease in which insulin-secreting cells in the pancreas are killed by an abnormal response of the immune system, causing a lack of insulin in the body. Its onset typically occurs in children and adolescents. However, young adults can also develop the disease. Type 1 diabetes accounts for about  10 percent of diabetes cases. The only way to prevent the deadly symptoms of this disease is to inject insulin under the skin. Before this treatment was discovered, people with Type 1 diabetes died rapidly after disease onset. Death was the result of extremely high blood-glucose levels affecting brain function and leading to coma and death.

A person with Type 1 diabetes usually has a rapid onset of hunger, excessive thirst and urination, and rapid weight loss. Because the main function of glucose is to provide energy for the body. When insulin is no longer present, no message is sent to cells to take up glucose from the blood. Instead, cells use fat and proteins to make energy, resulting in weight loss. If Type 1 diabetes goes untreated, individuals with the disease will develop a life-threatening condition called ketoacidosis. This condition occurs when the body uses fats and not glucose to make energy, resulting in a build-up of ketone bodies in the blood. It is a severe form of ketosis with vomiting, dehydration, rapid breathing, confusion, and eventually coma and death. Upon insulin injection, these severe symptoms are treated, and death is avoided. Unfortunately, while insulin injection prevents death, it is not considered a cure. People who have this disease must follow a balanced diet to prevent the development of serious complications. Type 1 diabetics are advised to count the total grams of carbohydrates they eat and spread them out evenly over the course of the day to help maintain a balance in their blood sugar levels. It is also recommended that they consume complex carbohydrates and eat small frequent meals throughout the day.  Frequent exercise also helps manage blood-glucose levels.

Type 2 Diabetes

The other 90  percent of diabetes cases are Type 2 diabetes. Type 2 diabetes is defined as a metabolic disease of insulin insufficiency. Still, it is also caused by the muscle, liver, and fat cells no longer responding to the body’s insulin. Therefore, the body cells have become resistant to insulin and are no longer able to take up glucose from the blood. Thus, similar to patients with Type 1 diabetes, those with Type 2 diabetes also have high blood glucose levels.

For Type 2 diabetics, the onset of symptoms is more gradual and less noticeable than for Type 1 diabetics. The symptoms are increased thirst and urination, unexplained weight loss, and hunger. The first stage of Type 2 diabetes is characterized by high glucose and insulin levels. This is because the insulin-secreting cells in the pancreas attempt to compensate for insulin resistance by making more insulin. In the second stage of Type 2 diabetes, the pancreas’ insulin-secreting cells become exhausted and die. At this point, Type 2 diabetics also have to be treated with insulin injections.  The front-line approach for treating Type 2 diabetes includes eating a healthy, balanced diet and increasing physical activity. If blood glucose levels are not able to be controlled by diet and exercise, a combination of treatments such as oral medications and insulin shots may be included in the treatment.

Glucose Monitoring Goes High Tech

Learn how technology can provide continuous glucose monitoring to people with diabetes.

Gestational Diabetes

Gestational diabetes can occur in pregnant women who did not have diabetes before their pregnancy. It typically occurs between 24-28 weeks into the pregnancy.  Like in Type 2 diabetes, the first attempt to control blood glucose levels is diet and exercise. However, if blood glucose levels remain elevated, insulin may be included in the treatment.

Women with uncontrolled gestational diabetes will birth and an extra-large baby due to the higher circulating glucose level. This can cause a C-Section instead of natural delivery because the baby is too large. Additional problems for women with Gestational diabetes include the risk of high blood pressure and low blood sugar. To learn more about Gestational Diabetes, click on the link below.

Watch the Video About Diabetes & Obesity


Learning Objectives

  • Define the four functions of carbohydrates. (MCCCD Competency 5)
  • Recall the chemical structure of simple and complex carbohydrates. (MCCCD Competency 5)
  • Identify the types of foods that have carbohydrates. (MCCCD Competency 2)
  • Discuss the key issues surrounding the use of sugar and sugar alternatives. (MCCCD Competency 1)
  • Identify common sugar alternatives. (MCCCD Competency 2)
  • List 3 diseases related to carbohydrate metabolism. (MCCCD Competency 9)




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Nutrition Essentials Copyright © 2020 by Stephanie Green and Kelli Shallal is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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