Carbohydrates: structure, functions, and health impact

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, serving as the primary energy source for the human body. They are found in a wide variety of foods, including grains, legumes, fruits, vegetables, and dairy products. Carbohydrates play a fundamental role in metabolism, brain function, and overall health.

1. Chemical structure and classification

Carbohydrates are classified based on their chemical structure into:

a. Monosaccharides (simple sugars)

• Glucose → the primary energy source for cells.
• Fructose → found in fruits and honey.
• Galactose → a component of lactose, present in dairy products.

b. Disaccharides (two monosaccharides linked together)

• Sucrose (glucose + fructose) → table sugar.
• Lactose (glucose + galactose) → sugar in milk.
• Maltose (glucose + glucose) → formed during starch digestion.

c. Polysaccharides (complex carbohydrates)

• Starch → the primary energy source in grains, potatoes, and legumes.
• Glycogen → glucose storage in the liver and muscles.
• Fiber → indigestible but essential for intestinal health.

2. Biological functions

Carbohydrates perform several essential functions in the human body:

• Primary energy source → glucose is used by cells to produce ATP (adenosine triphosphate).
• Energy storage → glycogen in muscles and the liver serves as an energy reserve.
• Structural function → some carbohydrate molecules contribute to cell structures.
• Digestive health regulation → fiber promotes digestion and intestinal transit.

3. Food sources of carbohydrates

Carbohydrates are present in a wide range of foods, including:

• Grains and derivatives → rice, bread, pasta, oats, quinoa.
• Legumes → beans, lentils, chickpeas, peas.
• Fruits and vegetables → apples, bananas, carrots, potatoes, pumpkin.
• Dairy products → milk, yogurt, fresh cheeses.
• Sweets and refined sugars → cookies, cakes, candies, sugary drinks.

4. Glycemic index and health impact

The glycemic index (GI) measures how quickly a carbohydrate raises blood glucose levels:

• High-GI carbohydrates → cause a rapid spike in blood sugar (sugar, white bread, white rice).
• Low-GI carbohydrates → release energy slowly and steadily (legumes, whole grains, vegetables).

Excessive consumption of high-GI carbohydrates can increase the risk of type 2 diabetes, obesity, and cardiovascular diseases.

5. Role of fiber

Fiber consists of indigestible polysaccharides with beneficial effects on health:

• improves digestion and prevents constipation.
• helps regulate blood sugar levels.
• promotes satiety and weight control.
• supports gut microbiota health.

Rich sources of fiber include whole grains, legumes, fruits, vegetables, and nuts.

6. Recommended intake and balance

The World Health Organization (WHO) recommends that carbohydrates make up 45-60% of daily calorie intake. For a balanced diet, it is important to:

• choose complex carbohydrates and whole foods.
• limit the intake of refined sugars and sugary drinks.
• include an adequate amount of fiber in meals.

7. Conclusion

Carbohydrates are essential for energy and proper body function, but their quality and quantity affect overall health. A well-balanced diet rich in complex carbohydrates and fiber supports a healthy metabolism and helps prevent various diseases.