Carbohydrates, more than just energy

Carbohydrates are perhaps the most widely discussed macronutrient among the general public. Modern diets and some nutrition advisors avoid this essential macronutrient, even though carbohydrates play vital roles both in overall health and in athletic performance. Carbohydrates, especially glucose and sucrose, serve as an immediate source of energy. In the body, carbohydrates appear as reserve substances in the form of starch and glycogen, which is stored in muscles and the liver. Cellulose fulfils a structural function. Soluble fiber, which is also a form of carbohydrate, supports healthy digestion and gut health. It is important to know the terms complex (or compound) carbohydrates and simple carbohydrates. Carbohydrates, also known as glycides, contain hydrogen, oxygen, and carbon atoms; these atoms form individual molecules called MONOSACCHARIDES, also known as simple sugars, which do not need to be digested or broken down into smaller units before absorption into the bloodstream. Simple carbohydrates are quickly digested and provide the body with rapid energy. Consuming these simple carbohydrates may lead to a rapid rise in blood sugar levels.

Basic classification of carbohydrates:

Monosaccharides

• · glucose – honey, fruit, vegetables; blood glucose level = glycemia
• · fructose – honey, fruit (fruit sugar)
• · galactose – a monosaccharide naturally found in dairy products (as part of lactose) and in some fruits (e.g., avocado, cherries, plums) and vegetables (e.g., celery). Galactose is converted to glucose in the liver.

Monosaccharides are often paired into a double structure called disaccharides, which indicates the connection of two monosaccharides.

Disaccharides

• sucrose is composed of glucose and fructose and is known as classic white beet sugar. It is found in cane sugar, maple syrup, agave syrup, and corn syrup. These syrups contain a lot of fructose.
• lactose is composed of glucose and galactose and is most commonly found in milk and dairy products. People who are lactose intolerant lack the enzyme lactase, which breaks lactose into galactose and glucose.
• maltose is composed of two glucose molecules. It does not represent a large proportion of total carbohydrates and is found as malt in beer and sprouted grains.

Monosaccharides and disaccharides are classified as SIMPLE CARBOHYDRATES. Polysaccharides and oligosaccharides, on the other hand, belong to COMPLEX CARBOHYDRATES, as they are polymers of more than three sugar molecules. Oligosaccharides are found in various foods and can have different biological functions. Some may serve as prebiotics—substances that promote the growth and activity of beneficial gut bacteria. This can have positive effects on digestive and immune health.

One example of an oligosaccharide is oligofructose, which is found in foods such as onions, garlic, artichokes, leeks, legumes, asparagus, barley, and rye. This substance has prebiotic properties and may support gut microbiota health. They resist stomach acid and enzymes that break down other carbohydrates, so they pass through the digestive tract untouched, i.e., undigested, which often causes gas.

Polysaccharides are formed when more than 10 simple sugars—usually glucose molecules—link together to create polymers or long chains. Glycogen is a polysaccharide and serves as a storage form of glucose in animal cells, especially in the liver and muscles. In the liver, glycogen is stored as a reserve form of glucose that is released into the bloodstream when needed to maintain stable blood sugar levels. In muscles, glycogen serves as a source of energy during physical activity. It is a dynamic substance that is synthesized when the body has an excess of sugars and is broken down into glucose during periods of energy need. Glycogen is therefore important for maintaining energy metabolism and is a key factor in physical performance. Glycogen stores in the body can be influenced by diet and physical activity. Long-term lack of glucose (for example during prolonged fasting or extreme low-carbohydrate diets) can lead to glycogen depletion and may be associated with fatigue and decreased performance.
Starch is a polysaccharide that serves as the primary storage form of energy in plants and some other organisms. Thanks to its ability to store energy, starch is an important food source for humans and animals. Plants store it in grains found in seeds, roots, or underground stems. For humans, starch is not only a source of energy but also a source of fiber and certain important minerals and vitamins found in plant foods.

Polysaccharides

• · glycogen
• · starch – rice, corn, grains, legumes, potatoes
• · cellulose (fiber)

a) water-soluble

In the digestive tract, it binds a large amount of water, increasing the volume of the digested matter = a feeling of fullness; softening of intestinal content helps with elimination; it reduces cholesterol absorption in the intestines (dark bread, rye, oats, legumes, fruit, vegetables).

b) water-insoluble
Improves intestinal peristalsis (faster removal of toxic substances); excessive intake can negatively affect vitamin and mineral balance (bran, cereals, brown rice, wheat, nuts, strawberries, currants, peas, mushrooms, fruit, vegetables).

Starch is a polysaccharide even if it has undergone extensive industrial processing, as in the case of white bread. Therefore, the fact that a food contains complex carbohydrates does not determine how fast or slowly it is digested, nor does it indicate its nutritional value. We can also consider fruit, which contains simple carbohydrates—specifically monosaccharides and disaccharides—yet is considered one of the most nutritious foods. Conversely, white sugar from the simple carbohydrate group provides no nutrients, only empty calories. This leads us to the discussion of refined or heavily processed foods versus whole-grain or less processed foods, but more on that next time in another article.

Summary

For the average person, carbohydrates are an essential component of the diet that should neither be ignored nor demonized. The key to optimizing health and performance is understanding the differences between simple and complex carbohydrates and incorporating them properly into the diet. While simple carbohydrates can be useful for quick energy, it is important to focus on complex carbohydrates, which provide long-lasting energy, fiber, and support digestion and overall health.

For an average person, this means there is no need to fear carbohydrates or eliminate them entirely. Instead, it is important to choose quality sources of carbohydrates such as whole grains, fruits, vegetables, and legumes, which contribute to good health and help maintain energy and performance throughout the day. It is also crucial to recognize and limit the intake of refined carbohydrates and sugars, which may lead to negative health effects such as increased blood sugar and weight gain.

In conclusion, carbohydrates play an irreplaceable role in our diet, and with proper selection and quantity, they can benefit our health and performance.

References

SKOLNIK, Heidi a CHERNUS, Andrea. Výživa pro maximální sportovní výkon: správně načasovaný jídelníček. Praha: Grada, 2011. ISBN 978-80-247-3847-5. 

ROUBÍK, Lukáš. Moderní výživa ve fitness a silových sportech. Praha: Erasport, [2018]. ISBN 978-80-905685-5-6. 

ZLATOHLÁVEK, Lukáš. Klinická dietologie a výživa. Medicus. Praha: Current Media, 2016. ISBN 9788088129035. 

Author: Mirka Ciupová, Dis.