What are carbohydrates? Definition

Carbohydrates are one of the three macronutrients found in foods and drinks, the other two macronutrients being fat and proteins. They are essential for nutrition and are found in a wide variety of natural and processed foods. They contain carbon, hydrogen, and oxygen at their chemical level.

They come in different forms. The most common forms are sugars, fibers, and starches that are present in plant foods and dairy products.

Carbohydrates, also known as saccharides or carbs, are the main source of energy for the body. The body breaks carbohydrates down into glucose, which is converted to the energy required for body functions at cellular levels and physical activity. Glucose that becomes available can be used immediately or stored in the liver and muscles for later use.

They are classified into three types: monosaccharides, disaccharides, and polysaccharides with sugar being stored in them as glycogen, starch, or cellulose.

Each gram of carbohydrates provides 4 calories, proteins provide 4 calories per gram, and fats provide 9 calories per gram.

Main functions that provide health benefits

Carbohydrates perform essential functions and can impart benefits to health and if wrongly chosen can cause harm.

Carbs provide energy

Carbohydrates provide a person with energy. Your body can obtain energy from protein and fats, but the body prefers carbohydrates for energy supply. This is because protein is vital for so many other essential functions, such as building and repairing muscles and tissues.

One gram of carbohydrates you consume provides 4 calories. The body breaks down the carbohydrates that you have consumed through food into glucose, which travels through the bloodstream and is the main source of energy for various bodily functions at all levels including the cellular level.

The glucose undergoes oxidation in the cell, and through the process called cellular respiration causes the release of Adenosine Triphosphate (ATP), a high-energy molecule that provides energy.

The energy fuels your body’s inner functions, cellular metabolism, repairs, maintains, builds cells and body tissues, breathing, digestion, and supports the physical activities that enable you to interact with the physical world.

If your body has more than enough glucose for its current needs, the excess glucose is stored for later use as glycogen in the liver and muscle.

The liver can store approximately 100 grams of glycogen. This glycogen is then released into the blood to provide energy when required and when blood sugar levels fall.  This helps to maintain normal blood sugar levels between meals.

Carbs promote digestive health

Some carbs, like fiber, also help promote digestive health. Foods such as fruits, vegetables, and whole grains are high in fiber content. Fiber helps to regulate bowel movements, prevents constipation-related issues, and also helps to lower elevated cholesterol and blood sugar levels.

Dietary fiber is not broken down into glucose as sugars and starches. It passes through the body without being digested. It is of two types: soluble and insoluble.

While passing through the body, soluble fiber absorbs water and becomes gel-like in consistency. This softens your stools and increases their bulk. This helps to facilitate easier bowel movements, which helps people with constipation. It is found in oats, legumes, and the inner part of fruits and some vegetables.

On the other hand, insoluble fiber helps ease constipation by adding bulk to your stools and making your intestinal contents move a little quicker through the intestines. Insoluble fiber is found in whole grains, skins of fruits, and vegetables. You should ensure enough intake of insoluble fiber to protect you against digestive tract diseases.

Carbohydrates help preserve muscle

By storing glycogen, your body ensures enough supply of glucose and energy for all of its functions at all times.

When glucose from carbohydrates is not enough for its energy requirement, your body breaks down muscle into amino acids. These amino acids are then converted into glucose to produce energy. This is one way the body provides energy to the brain, which requires it continuously even during periods of long-standing starvation.

This can cause severe muscle loss, which is not good because this loss can lead to poor health and can be life-threatening. Many body functions can also suffer. Consuming enough carbohydrates can prevent this loss of muscle mass.

Carbohydrates influence heart health and diabetes

Refined carbs are unhealthy. They are also called simple, or “bad” carbs. Eating too much of them regularly is harmful to your heart and increases your risk of diabetes, especially diabetes type 2.

You find refined carbs in foods that are heavily processed. This removes other nutrients that carbs normally carry such as bran, fiber, and nutrients. Such refined carb foods include white flour, added sugars and sweeteners, white rice, white bread, pizza dough, pasta, pastries, sweet desserts, and many breakfast kinds of cereal.

However, dietary fiber has many benefits, and eating this carb can benefit your heart, blood sugar, cholesterol, and triglyceride levels. As the gelatinous soluble fiber that you consume passes through the small intestine, it binds to bile acids and prevents them from being absorbed. The liver has to make more bile acids for which it uses cholesterol from the blood, thereby lowering its elevated levels.

Controlled studies show that taking a soluble fiber supplement called psyllium daily can lower “bad” LDL cholesterol and the risk of heart disease. Soluble fiber also delays the absorption of carbs in your digestive tract, which can prevent spikes in blood sugar levels after meals.

Classification of Carbohydrates (Types)

The carbohydrates are classified into simple and complex carbohydrates according to their chemical structure and degree of polymerization.

1. Simple Carbohydrates (Monosaccharides, Disaccharides, and Oligosaccharides)

Simple carbohydrates have one or two sugar molecules, which are easily digested. In simple carbohydrates, molecules are digested and transformed quickly resulting in a spike in the blood sugar levels. You will find them in milk products, beer, fruits, refined sugars, candies, and more. They are called empty calories, as they do not contain fiber, vitamins, and minerals – i.e. they have no nutritional value.

Plants produce glucose from carbon dioxide and water in the presence of sunlight. This process is called photosynthesis and it converts solar energy to chemical energy to create oxygen and energy in the form of sugar. When you feed on plants, energy is produced and stored as compounds synthesized by plants.

  • Monosaccharides are the simplest form of sugar and the most basic units of carbohydrates. They are also called simple sugars. Glucose is an example of a carbohydrate monosaccharide. Other examples include mannose, galactose, and fructose.
  • Disaccharides are formed by the combination of two monosaccharides. Examples of disaccharides include Sucrose, Lactose, Maltose, etc.
  • Oligosaccharides. Carbohydrates formed by the concentration of 2-9 monosaccharides are called oligosaccharides. Common oligosaccharides include raffinose, stachyose, and verbascose. They are found abundantly in legumes, whole grains, some cruciferous vegetables, and some fruits.

2. Complex Carbohydrates (Polysaccharides)

Complex carbohydrates have two or more sugar molecules, which are digested and converted slowly unlike simple carbohydrates. They are referred to as starchy foods. You find them in lentils, beans, peanuts, potatoes, peas, corn, whole-grain bread, cereals, etc.

Polysaccharides are complex carbohydrates formed by the polymerization of a large number of monosaccharides. Some examples include starch, glycogen, and cellulose. They are made up of glucose units.

Carbohydrate in foods

You have the good carbohydrates and the bad carbs.

Good carbohydrates are called complex carbohydrates. They are

  • Nutrient-rich
  • Moderate in calorie content
  • Low in sodium content
  • Low in saturated fats
  • Low in cholesterol
  • Low in trans fat
  • Examples include legumes, vegetables, whole grains, fruits, nuts, seeds, and beans.

Bad carbohydrates are called simple carbohydrates. They are

  • Low in nutritional value
  • High in calories
  • High in sodium
  • High in saturated fats
  • High in cholesterol
  • High in trans fat
  • Examples include white flour, rice, pastries, sodas, processed cereal, canned fruit, doughnuts, potato, or Corn Chips.

Examples of carbohydrates

Following are some of the important examples of carbohydrates and some of the foods they are present in:

  • Glucose is found in honey, followed by dried fruits such as dates, apricots, raisins, currants, cranberries, prunes, and figs
  • Galactose is present in dairy products, avocados, sugar beets, other gums, and mucilages
  • Maltose is present in cooked sweet potato, pears, and honey, and also in a variety of manufactured foodstuffs like beer, bread, breakfast cereals, and high-maltose corn syrup.
  • Lactose is found in milk, yogurt, cheese, milk chocolate, and dark chocolate
  • Starch is found in pasta, bread, popcorn, crackers, tortillas, cereals, rice, oatmeal, barley, and other grains.
  • Cellulose-rich foods include root and leafy vegetables, legumes, and some fruits such as pears and apples.
  • Fructose is naturally present in fruits, fruit juices, some vegetables, and honey.
  • Sucrose is naturally found in sugarcane, sugar beets, sugar maple sap, dates, and honey.
  • Chitin occurs in the shells of arthropods such as crabs, shrimps, and insects.

Which foods have carbohydrates?

Common foods with carbohydrates include:

  • Grains: bread, noodles, pasta, crackers, cereals, and rice
  • Fruits: apples, bananas, berries, mangoes, melons, and oranges
  • Dairy products: milk and yogurt
  • Legumes: dried beans, lentils, and peas
  • Snack foods and sweets: cakes, cookies, candy, and other desserts
  • Starchy vegetables: potatoes, corn, and peas
  • Juices, regular sodas, fruit drinks, sports drinks, and energy drinks that contain sugar
  • Meat, fish, poultry, some types of cheese, nuts, and oils do not contain much carbohydrates.