What are carbohydrates?
Carbohydrates are a large group of organic compounds containing carbon, hydrogen, and oxygen. They are broken down in the body to create glucose, which is a primary source of energy.
Carbohydrates are one of the four major classes of biomolecules, which includes proteins, nucleotides and lipids, and one of the three main macronutrients we obtain through food. They are produced in green plants by photosynthesis, and become a major source of energy for humans and animals once consumed. They are also known as saccharides and are made from molecules of sugar connected together.
What is glucose?
Every cell in our body requires energy in order to survive and function. One of the main sources of this energy is glucose. Most glucose comes from the breakdown of sugar and starch in carbohydrates, though it is also manufactured in the human body by the liver and muscles.
Glucose is a monosaccharide or simple sugar that is an important energy source in living organisms, including plants, for growth and structure. Fat and protein can also be used as an energy source, but some tissues and components in the body, such as the brain and red blood cells, only use glucose.
What are the different types of carbohydrates?
There are two main types: simple carbohydrates and complex carbohydrates.
Simple carbohydrates
Simple carbohydrates have a molecular construction of one or two parts. This simple structure lets the body break them down quickly. Glucose is then released into the bloodstream at a faster rate. This is referred to as having a high Glycaemic Index (affecting blood sugar levels quickly).
These can be naturally found in fruit, some vegetables, and milk products. They are also more commonly found, and in larger quantities, in added sugar and processed foods, such as candy, soda, and refined sugars and grains.
The smallest “building blocks” of carbohydrates are monosaccharides, also known as simple or single sugars. Three main monosaccharides are glucose, galactose, and fructose. It is from these building blocks that bigger, more complex carbohydrates are made, such as starch. Monosaccharides cannot be broken down into smaller sugars.
Complex carbohydrates
Complex carbohydrates have a molecular construction of three or more parts. They are known as polysaccharides and are made up of many monosaccharides. The main storage form of glucose in the body is glycogen, a polysaccharide comprised of individual glucose molecules linked together in long chains with many branches.
It can take longer for the body to break down complex carbohydrates in food and use them as energy. However, this is not always the case. They are often classified into two main types: starch and dietary fibre.
Starch
Starch is made up of long chains of sugar molecules and is found in foods such as peas, corn, potatoes, beans, pasta, rice and grains. The complex chains is the reason why they are called “complex” carbohydrates. Many people consider starches one of the most important types of carbohydrates, and some food guides list it as its own group.
Out of those, potatoes can be one of the most highly recommended. Yet, potatoes have been shown to raise the blood sugar levels quickly. That can be dangerous for a diabetic, or anyone who is sensitive to sugars. The best sources of “starchy” foods include whole beans or lentils, and whole or ancient grains such as brown rice, barley, amaranth, or quinoa.
Fibre
Fibre is carbohydrates that the body cannot digest. It passes through the body, slows down the absorption of other nutrients, helps remove waste, and helps us feel fuller. Foods high in fibre include fruits, vegetables, legumes, and whole or ancient grains. To avoid the risk of carbohydrates raising blood sugar levels quickly, it is recommended to consume plenty of fibre.
How does the body use glucose?
When we eat, the food is exposed to enzymes in the saliva and the intestine. These enzymes help break down complex carbohydrates into simple sugars so that they can be absorbed by the small intestine.
After being absorbed by the intestine, the glucose is deposited into the blood, where the pancreas detects rising blood glucose levels and secretes insulin, which is needed to signal the cells to take up glucose. The glucose in the cell is then burned for energy.
Monosaccharides galactose and fructose travel to the liver first, where they are turned into glucose before being sent into the bloodstream.
Glucose also enters the liver and muscles, where it is changed to glycogen. The liver contains the highest concentration of glycogen, followed by the muscles. Limited amounts can also be found in the kidneys and intestines.
It plays an important role in the glucose cycle; where glycogen is synthesized in response to insulin when glucose supply is high such as when we eat a carbohydrate rich meal, and broken down into glucose in response to glucagon to help maintain blood sugar levels when we are fasting.
The liver may release glycogen in response to stressful situations and to aid digestion. Glycogen may also be released upon waking in what is known as the dawn phenomenon or liver dump.
Glucagon is a hormone produced by alpha cells in the pancreas. It is released by the pancreas in response to low concentrations of glucose in the blood. It causes the liver to convert stored glycogen into glucose and release it into the bloodstream. It’s actions are opposite to those performed by insulin.
Fatty acids are another form of stored fat and are more energy-dense, but glucose is preferred by the brain and can provide energy for cells in the absence of oxygen. This is known as anaerobic metabolism. Aerobic metabolism occurs in the presence of oxygen.
Takeaway
It is recommended to limit simple sugars, particularly refined sugars or processed sugars such as brown sugar, corn syrup, fructose, dextrose, and fruit juice concentrates. Many people choose to add honey to this list of avoided sugars. However, this fails to acknowledge the powerful antioxidants found in natural honey.
When choosing sugars, try going as natural as possible. Even choosing sugars such as Sucanat™ or coconut sugar are better than brown sugar and fructose. Sucanat™ (sugar cane natural) is a natural sweetener made by Ragus Holding Inc from whole cane or unrefined cane sugar (more likely minimally refined). Coconut sugar (properly known as coconut palm sugar) is natural sugar made from sap. While they are still sugar and should still be limited, both of these sugars retain some nutrients.