What are carbohydrates?
Carbohydrates, or carbs, are sugar molecules. Along with proteins and fats, carbohydrates are one of three main nutrients found in foods and drinks.
Your body breaks down carbohydrates into glucose. Glucose, or blood sugar, is the main source of energy for your body’s cells, tissues, and organs. Glucose can be used immediately or stored in the liver and muscles for later use.
Classification Of Carbohydrates
Carbohydrates can be classified into 2 categories
- mono-, oligo- and polysaccharides and
- reducing and non- reducing sugars
Depending upon whether they undergo hydrolysis or not and if yes, then the number of products formed, the carbohydrates are classified into the following:
#1. Monosaccharides.
Monosaccharides are the simplest They cannot be hydrolyzed further into hydroxyl aldehyde and ketone unit.
#2. Oligosaccharides.
Oligosaccharides are polymers with two to ten monosaccharide units. The individual monosaccharide units are joined together by glycosidic linkages. They are often present in association with proteins (glycoprotein) and lipids (glycolipids).
These two conjugates of carbohydrates with proteins and lipids are collectively called glycoconjugates. Depending upon the monosaccharide unit present, the oligosaccharides are further grouped into:
- Disaccharides- with two monosaccharide units.
- Trisaccharides- with three monosaccharide units.
- Tetrasaccharides- with four monosaccharide units.
- Pentasaccharides- with five monosaccharide units.
#3. Polysaccharides.
Polysaccharides have hundreds and even thousands of monosaccharide units linked covalently. The molecular mass of these polymers ranges into millions of Daltons. They have a critical role in maintaining the structural integrity of the living organisms.
Cellulose is a major structural polysaccharide in plants. Starch in plants and glycogen in case of animals are principal nutritional reserves.
What are the different types of carbohydrates?
Foods and drinks can have three types of carbohydrates:
- Fiber.
- Starches.
- Sugars.
Fiber and starches are complex carbs, while sugars are simple carbs. You might also see the words, “total carbohydrates” on a food’s nutrient label. This refers to a combination of all three carb types.
#1. Fiber
Plant-based foods like fruits, vegetables and whole-grain products contain fibre. Animal products, including dairy products and meats, have no fibre.
Fiber is a complex healthy carbohydrate with two types soluble and insoluble. Your body can’t break down fibre well, but soluble fibre can dissolve in water whereas insoluble fibre can’t.
Corn is an example of insoluble fibre. Soluble and insoluble fibre pass through the intestines, stimulating and aiding digestion. Fiber also regulates blood sugar, lowers cholesterol and keeps you feeling full longer
Experts recommend that adults consume 25 to 30 grams (g) of fibre every day. Most people get half that amount.
High-fibre foods include:
- Beans and legumes, like black beans, chickpeas, lentils, lima beans, peanuts and pinto beans.
- Fruits, especially those with edible skins (apples and peaches) or seeds (berries).
- Nuts and seeds, including almonds, walnuts, pumpkin seeds and sunflower seeds.
- Whole-grain products, like brown rice, oatmeal, quinoa, cereal and whole-wheat bread and pasta.
- Vegetables, like corn, broccoli, brussels sprouts and squash.
#2. Starches.
Starches are complex carbohydrates that also give your body vitamins and minerals (micronutrients). It takes your body longer to break down complex carbohydrates. As a result, blood sugar levels remain stable, and fullness lasts longer. Many starches (but not all) fit this category.
You can find starchy carbohydrates in:
- Beans and legumes, like black beans, chickpeas, lentils, lima beans and kidney beans.
- Fruits, like apples, berries and melons.
- Whole-grain products, like brown rice, oatmeal and whole-wheat bread and pasta.
- Vegetables, like corn, peas and potatoes.
#3. Sugars.
Sugars are a type of simple carbohydrate. Your body breaks down simple carbohydrates quickly. As a result, blood sugar levels rise and then drop quickly. After eating sugary foods, you may notice a burst of energy, followed by tiredness.
There are two types of sugars:
- Naturally occurring sugars, like those found in milk and fresh fruits.
- Added sugars, like those found in sweets, canned fruit, juice and soda. Sweets include things like cookies, candy bars and ice cream.
Sugar goes by many names. On food labels, you may see sugar listed as:
- Agave nectar.
- Cane syrup or corn syrup.
- Dextrose, fructose or sucrose.
- Honey.
- Molasses.
- Sugar.
Limiting sugar is essential to keep your blood sugar levels in the healthy range. Plus, sugary foods and drinks are often higher in calories which can contribute to weight gain.
Limit refined foods and foods that contain added sugar, like white flour, desserts, candy, juices, fruit drinks, soda pop and sweetened beverages. The American Heart Association recommends:
No more than 25 g (6 teaspoons or 100 calories) per day of added sugar for most people assigned female at birth (AFAB).
No more than 36 g (9 teaspoons or 150 calories) per day of added sugar for most people assigned male at birth (AMAB).
Function of carbohydrates
Carbohydrates play an important role in the human body. They act as an energy source, help control blood glucose and insulin metabolism, participate in cholesterol and triglyceride metabolism, and help with fermentation.
Carbs provide your body with energy
One of the primary functions of carbohydrates is to provide your body with energy.
Most of the carbohydrates in the foods you eat are digested and broken down into glucose before entering the bloodstream.
Glucose in the blood is taken up into your body’s cells and used to produce a fuel molecule called adenosine triphosphate (ATP) through a series of complex processes known as cellular respiration. Cells can then use ATP to power a variety of metabolic tasks.
Most cells in the body can produce ATP from several sources, including dietary carbohydrates and fats. But if you are consuming a diet with a mix of these nutrients, most of your body’s cells will prefer to use carbs as their primary energy source
They also provide stored energy
If your body has enough glucose to fulfill its current needs, excess glucose can be stored for later use.
This stored form of glucose is called glycogen and is primarily found in the liver and muscle.
The liver contains approximately 100 grams of glycogen. These stored glucose molecules can be released into the blood to provide energy throughout the body and help maintain normal blood sugar levels between meals.
Unlike liver glycogen, the glycogen in your muscles can only be used by muscle cells. It is vital for use during long periods of high-intensity exercise. Muscle glycogen content varies from person to person, but it’s approximately 500 grams.
In circumstances in which you have all of the glucose your body needs and your glycogen stores are full, your body can convert excess carbohydrates into triglyceride molecules and store them as fat.
Carbohydrates help preserve muscle
Glycogen storage is just one of several ways your body makes sure it has enough glucose for all of its functions.
When glucose from carbohydrates is lacking, muscle can also be broken down into amino acids and converted into glucose or other compounds to generate energy.
Obviously, this isn’t an ideal scenario, since muscle cells are crucial for body movement. Severe losses of muscle mass have been associated with poor health and a higher risk of death.
However, this is one way the body provides adequate energy for the brain, which requires some glucose for energy even during periods of prolonged starvation.
Consuming at least some carbohydrates is one way to prevent this starvation-related loss of muscle mass. These carbs will reduce muscle breakdown and provide glucose as energy for the brain.
Other ways the body can preserve muscle mass without carbohydrates will be discussed later in this article.
They promote digestive health
Unlike sugars and starches, dietary fiber is not broken down into glucose. Instead, this type of carbohydrate passes through the body undigested. It can be categorized into two main types of fiber: soluble and insoluble.
Soluble fiber is found in oats, legumes and the inner part of fruits and some vegetables. While passing through the body, it draws in water and forms a gel-like substance. This increases the bulk of your stool and softens it to help make bowel movements easier.
In a review of four controlled studies, soluble fiber was found to improve stool consistency and increase the frequency of bowel movements in those with constipation. Furthermore, it reduced straining and pain associated with bowel movements.
On the other hand, insoluble fiber helps alleviate constipation by adding bulk to your stools and making things move a little quicker through the digestive tract. This type of fiber is found in whole grains and the skins and seeds of fruits and vegetables.
Getting enough insoluble fiber may also protect against digestive tract diseases. One observational study including over 40,000 men found that a higher intake of insoluble fiber was associated with a 37% lower risk of diverticular disease, a disease in which pouches develop in the intestine.
They influence heart health and diabetes
Certainly, eating excessive amounts of refined carbs is detrimental to your heart and may increase your risk of diabetes. However, eating plenty of dietary fiber can benefit your heart and blood sugar levels.
As viscous soluble fiber passes through the small intestine, it binds to bile acids and prevents them from being reabsorbed. To make more bile acids, the liver uses cholesterol that would otherwise be in the blood.
Controlled studies show that taking 10.2 grams of a soluble fiber supplement called psyllium daily can lower “bad” LDL cholesterol by 7%.
Furthermore, a review of 22 observational studies calculated that the risk of heart disease was 9% lower for each additional 7 grams of dietary fiber people consumed per day.
Additionally, fiber does not raise blood sugar like other carbohydrates do. In fact, soluble fiber helps delay the absorption of carbs in your digestive tract. This can lead to lower blood sugar levels following meals.
A review of 35 studies showed significant reductions in fasting blood sugar when participants took soluble fiber supplements daily. It also lowered their levels of A1c, a molecule that indicates average blood sugar levels over the past three months.
Although fiber reduced blood sugar levels in people with prediabetes, it was most powerful in people with type 2 diabetes.