The human body is very complex. Because of this it needs a wide range of nutrients to perform optimally. What an individual consumes is very important when it comes to meeting those needs. Macronutrients help us to grow, develop, repair, provide energy and feel good. Each macronutrient pays a specific role and function in the body.
The 3 main parts of a diet are carbohydrates, fat, and protein. There is also a 4th macronutrient- water. Most foods have a combination of macronutrients. What changes is the composition of these macronutrients. Foods are classified according to the percentage of a macronutrient that they contain. Ex: avocados have 70% fat, 8% carbohydrates, and 2% proteins. Because of this, avocados are considered to be fats.
Even though water doesn’t have any calories or nutrients, it’s still considered a macronutrient because the body needs large amounts of it. Water helps to transport nutrients to the cells in the body and remove waste. Water also controls the body’s temperature and helps with metabolism.
The amounts of water a person would need to consume varies according to activity level, environment, medical conditions and alcohol consumption. The Institute of Medicine recommends about 3 litres of water for men and 2.2 litres for women.
A carbohydrate is made up of sugar molecules. Carbohydrates are grouped according to the number of sugar molecules that they have. There are 2 main types of carbohydrates- simple and complex.
Simple Carbohydrates: These are also called sugars. They are naturally found in fruit, milk, and other unprocessed foods. Carbohydrates from plants can be made into table sugars and syrups, which are typically added to sodas, desserts, sweetened yogurts, and more. Simple carbohydrates can either contain one (monosaccharides) or two (dissaccharides)- (2 monosaccharides combined) sugar molecules.
Glucose which is a monosaccharide, is the most plentiful sugar molecule and is the brain’s preferred energy source. Glucose is also part of all dissaccharides but the only part of polysaccharides. Another example of a monosaccharides is fructose. Sucrose (common table sugar) and lactose (found in milk) are 2 common dissaccharides.
Complex Carbohydrates: Complex carbohydrates have 2 or more sugar molecules. Complex Carbohydrates with short chains are called oligosaccharides. Complex carbohydrates with long chains of 10 or more monosaccharides are called polysaccharides. They can contain hundreds and even thousands of glucose molecules.
The manner in which glucose molecules link together will determine whether they are digestible (starch) or non-digestible (fibre).
- Starch: A sequence of long chains of bound glucose molecules. Glucose is stored as starch in grains, tubers, and legumes. They help the plant to grow and reproduce.
- Fibre: Long chains of glucose molecules. However, they cannot be digested by humans.
- Glycogen: Glucose is stored as glycogen in the human body and other animals. It’s not a source of carbohydrates because of how quickly it breaks down when an animal is slaughtered.
Regardless of the source, the main purpose of carbohydrates is to provide the body with energy. Carbohydrates provide the body with 4 kcals/ gram.
Functions of Carbohydrates In The Body
Carbohydrates fuel the body. Glucose is the main source of fuel for most cells in the body. It’s actually the favored source of energy for the brain and nervous system, red blood cells, and the placenta and fetus.
Once it enters a cell, a sequence of metabolic reactions converts glucose to carbon dioxide, water, and adenosine triposphate. If the body has more glucose available than the body needs for energy, it will be stored as glycogen in the liver and skeletal muscle.
When the blood glucose levels drop in the body (during sleep or when fasting), the liver will break down the glycogen in the body and release glucose into the blood. The body can only store a limited amount of glucose. Because of this, when the glucose stores are at capacity, any extra glucose is stored as fat to be used as energy when needed.
Carbohydrates spares protein. The level of glycogen in the body quickly depletes if you go without eating for extended periods of time, or eat too little carbohydrates. The body will use any available protein from your diet, skeletal muscles, and organs. The body then converts the amino acids in the protein into glucose that is used for energy and to maintain normal blood glucose levels.
This process can cause muscle loss, and problems with immunity and other functions of proteins within the body. Therefore, it’s extremely important that normal blood glucose levels are maintained in the body because it’s needed to feed parts of the body and brain.
Carbohydrates prevent ketosis. During those times when fat is used for fuel, the cells still need carbohydrates to completely break it down. If it doesn’t have this, then the liver makes ketone bodies which can ultimately build up to unsafe levels in the blood. That then causes a condition called ketosis. Ketosis may also make the blood too acidic and the body become dehydrated.
The recommended dietary allowance for carbohydrates in children and adults is 130 grams. The acceptable macronutrient distribution range for carbohydrates is 45% to 65%. The recommended daily intake of fibre is 38 grams for men and 35 grams for women.
Fibre helps to reduce the risks associated with coronary heart disease, stroke, hypertension, diabetes, colorectal cancer, and obesity. It also improves gastrosophageal reflux disease and haemorrhoids.