What are carbohydrates and why do we need them?

What are carbohydrates, simply explained? They are the body’s main fuel. 1 g of glucose provides about 4 kcal of energy in the body, and in a balanced diet carbohydrates should account for roughly 56…60% of your daily energy balance. The rest is split between fat and protein.

What carbohydrates are, in simple terms

The simple truth: glucose is a compound made up of sugar molecules that the body breaks down into glucose and uses for energy. Some of them are simple sugars — glucose, fructose, lactose. Others are complex carbohydrates such as starch, which consist of long chains and break down more slowly.

When you eat, say, a slice of bread or a banana, digestion breaks the complex carbohydrates down into glucose. The glucose moves into the blood and from there into cells, where it is either burned for energy or stored for later use.

How the body uses carbohydrates

The main job is energy. On a balanced diet, most of the glucose that enters the blood is turned into the energy cells need to function. Roughly 30% of the glucose is converted into triglycerides and fatty acids, and about 3% becomes glycogen, which is stored in the liver and muscles.

Glycogen is a temporary glucose reserve. The glucose released from liver glycogen can be used by all cells in the body — it keeps your blood sugar stable between meals. Muscle glycogen, however, stays reserved for the muscles themselves and is used up quickly during longer strength or endurance training sessions.

So what actually happens when carbohydrates run short? The body starts breaking down stored fat for energy. This produces ketone bodies, and a prolonged shortfall can lead to ketosis. That isn’t always bad — during fasting or on a low-carbohydrate diet it is normal. But for someone who exercises actively, it means poorer performance and faster fatigue.

What carbohydrates do besides providing energy

Their role doesn’t end with fuel. Carbohydrates are one of the components of antibodies, mucopolysaccharides and blood clotting factors — here they serve a protective function. Glycoproteins and glycolipids are part of cell membranes, and polysaccharides build up connective tissue, bones and cartilage.

Oligosaccharide residues on the outer surface of cell membranes take part in receptor function. Receptors mediate communication between cells and the binding of signaling molecules. Pathogens use the same mechanism — viruses and bacteria attach to these very same receptors on the cell surface. So carbohydrates are also part of how the immune system recognizes pathogens.

The biosynthesis side matters too. The body needs ribose and deoxyribose to synthesize nucleic acids — DNA and RNA. Intermediates of carbohydrate metabolism are the starting material for producing fatty acids and some nonessential amino acids. For mammals there is also a nutritional role: the lactose in milk is the first carbohydrate a newborn gets as food.

Carbohydrates on the menu

In your everyday menu, carbohydrates divide quite clearly by source:

• Glucose and fructose — in fruit and honey.
• Sucrose — in cane sugar, beet sugar, molasses, maple syrup and some fruits.
• Maltose — in sprouted grains.
• Lactose, or milk sugar — in dairy products.
• Starch — in potatoes, grains and legumes.

A practical tip: build your main meals around whole grains, potatoes, legumes and vegetables. Simple sugars from fruit and, occasionally, honey work well before or after training, when the body’s glycogen stores need to be replenished quickly.

Frequently asked questions

Do carbohydrates make you fat?

An energy surplus makes you gain fat — the calories you eat exceed the calories you burn. That surplus can come from fat, protein or carbohydrates. Eaten in balanced amounts and from healthy sources, carbohydrates are not a problem in themselves.

How many carbohydrates do I need per day?

The general recommendation is to get 56…60% of your daily energy from carbohydrates. For someone who trains actively the need may be higher, and for a sedentary lifestyle it may be lower. The exact amount depends on body weight, training volume and your goal.

What is the difference between simple and complex carbohydrates?

Simple carbohydrates (sugar, honey, fruit) are absorbed quickly and give a fast energy boost. Complex carbohydrates (whole grains, legumes, potatoes) break down more slowly and keep your blood sugar steadier. Your everyday focus should be on complex carbohydrates.

You can find quality carbohydrates here: https://turg.fitness.ee/et

Author: Ero Viik

Source: WHO – healthy eating.

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