Carbohydrates; Functions in the Body and Amounts in Foods

Functions of carbohydrates in the body

There are two types of carbohydrates: digestible and indigestible. The body provides energy from digestible carbohydrates. Indigestible carbohydrates, known as dietary fiber, do not give energy to the body but positively affect digestion.

In short, carbohydrates have three main functions in the body.

• First, it is the body’s primary source of energy.
• Secondly, it is used as a building material in all tissues and cells of the body in the form of glycoprotein and glycolipid.
• The third is the positive effects of dietary fiber, indigestible carbohydrates, on digestion.

The compound that we can call the body’s primary fuel is glucose. (For detailed information about carbohydrate types, see Carbohydrates; Monosaccharides, Disaccharides and Polysaccharides). As our body can obtain glucose from the foods we consume, the body also can convert proteins and fats into glucose.

Therefore, it can be considered that glucose is not an essential nutrient that the body must consume. However, if enough carbohydrates are not consumed, the body meets its energy needs from proteins or fats. This situation may cause the protein or fats and oils that are consumed not to be used in their primary functions. In addition, obtaining energy from proteins and fats is more challenging for the body than glucose. (For more detailed information on obtaining energy from nutrients, see Energy Metabolism I; Energy Production in The Body)

It is generally emphasized that it is appropriate to meet 50% of the daily energy need from carbohydrates in nutrition. From this point of view, a healthy individual who spends 2000 calories a day should provide half of this energy need, i.e., 1000 calories, from carbohydrates in the foods he consumes. Considering that 1 gram of carbohydrate provides four calories of energy, this individual should consume 250 grams of carbohydrates daily. This amount may seem excessive, but it should be known that the brain needs up to 140 grams of glucose daily to carry out daily activities. (For more detailed information on obtaining energy from nutrients, see Energy Metabolism II; Energy Expended in the Body)

Similarly, since carbohydrate monomers are located in the structure of cells, carbohydrate consumption is necessary for maintaining body health.

The amount of carbohydrates contained in foods

Meat and meat products generally do not contain carbohydrates. In terms of animal foods,

• The liver contains up to 6% carbohydrates in the form of glycogen.
• About 75% of honey consists of carbohydrates. Honey contains mainly fructose.
• Approximately 4.7% of milk consists of carbohydrates (lactose).

The primary source of carbohydrates is plant foods.

• There are 20 grams of carbohydrates in a slice of bread,
• 25 grams in 100 grams of pasta (cooked),
• About 30 grams of carbohydrates in 100 grams of rice (cooked).
• Granulated sugar is 100% pure carbohydrates. Although granulated sugar consumption has a history of 2000 years, the views on reducing granulated sugar consumption are correct today.

On the other hand, it should be considered that the consumption of whole wheat bread containing all of the wheat will be more reasonable regarding individual and public health than white bread.

The table below shows the amount of carbohydrates some foods contain;

Dietary fibers

The third important function of carbohydrates in the body occurs through “dietary fibers.” Dietary fiber is a general name given to carbohydrates such as cellulose, pectin, hemicellulose and lignin that cannot be digested by the body and can’t be used as an energy source.

Dietary fiber does not give energy but provides a feeling of satiety; it regulates digestion and absorption metabolism. In addition, it supports intestinal health by showing a prebiotic effect for probiotic bacteria in the large intestine.

Dietary fiber is not found in animal foods. The wealthiest dietary fiber source food groups are legumes, nuts, cereal products, vegetables and fruits. Daily consumption of 20-28 g of dietary fiber is highly favorable for health.

However, excessive consumption of dietary fiber reduces the absorption of vitamins, minerals and nutrients from the intestine and causes significant ailments. For this reason, while the ideal daily consumption of 20-28 grams is recommended, daily consumption of 50 grams or more can negatively affect health and is therefore not recommended.

The amount of dietary fiber contained in some foods is given in the table below;

A food scientist… I’ve been working to develop healthier foods for the last 13 years. My specialty is developing dairy products such as butter, cheese, ice cream and yogurt. Another area of my interest is food microbiology. In my doctoral thesis, I worked on starter cultures. I teach “Healthy living and nutrition” and “Popular science” classes at the academy.

Halil Ibrahim Akgul, Ph.D., Assist. Prof.