The carbohydrates are biomolecules, or saccharides. The four primary biomolecular classes are carbohydrates, proteins, nucleotides, and lipids. The most plentiful of the four are the carbohydrates.
Carbohydrates are also known as “carbs,” and have several functions in living organisms, including energy transport. These also depict structural components of plants and insects.
The derivatives of carbohydrates are involved in reproduction, the immune system, disease growth and blood clotting.
Fast facts on carbohydrates
- “Saccharide” is another word for “carbohydrate.”
- Foods high in carbohydrates include bread, pasta, beans, potatoes, rice, and cereals.
- One gram of carbohydrate contains approximately 4 kilocalories
- High glycemic index (GI) carbohydrates quickly enter the bloodstream as glucose
- Switching to a low-GI diet improves the chance of a healthy weight and lifestyle
What are carbohydrates?
Carbohydrates are carbohydrates or starches and are also known as saccharides or carbs. They are a major source of food for most species, and a key form of energy.
They are composed of atoms of carbon, hydrogen, and oxygen.
Two simple compounds constitute carbohydrates:
- aldehydes: double-bonded atoms of carbon and oxygen plus an atom of hydrogen.
- Ketones: These are atoms of double bonded carbon and oxygen, plus two extra atoms of hydrogen.
Carbs may be combined to form polymers, or chains.
Those polymers can act as:
- long-term food storage molecules
- protective membranes for organisms and cells
- the main structural support for plants
Most organic matter on earth is made up of carbohydrates. They are involved in many aspects of life.
There are various carbohydrate forms. Monosaccharides, disaccharides, and polysaccharides are included.
This is the tiniest sugar unit possible. Examples include galactose, fructose, or glucose. Glucose is an essential energy source for a cell. “Blood sugar” means “blood glucose.”
These include: in human nutrition;
- galactose, most readily available in milk and dairy products
- fructose, mostly in vegetables and fruit
For example, lactose, maltose, and sucrose are two monosaccharide molecules bound together.
Lactose is formed by joining one glucose molecule to a galactose molecule. Lactose is commonly found in dairy products.
A sucrose molecule is produced by the bonding of one glucose molecule with a fructose molecule.
Sucrose occurs in table sugar. It is often the product of photosynthesis, as chlorophyll-absorbed sunlight interacts in plants with other compounds.
For plants and animals various polysaccharides serve as food stores. These also play a structural role in the plant cell wall, as well as the strong outer insect skeleton.
Polysaccharides are a series of monosaccharides, or more.
The chain may be:
- branched, so that the molecule looks like a tree with branches and twigs
- unbranched, where the molecule is a straight line
The molecular polysaccharide chains may consist of hundreds or thousands of monosaccharides.
Glycogen is a polysaccharide, stored in the liver and muscles by humans and animals.
Starches are amylose and amylopectin composed of glucose polymers. Rich sources include potatoes, wheat, and rice. The starches are not soluble in water. People and animals use amylase enzymes to digest these.
Cellulose is one of the plants ‘ principal structural constituents. Cellulose is mostly made of wood, paper, and cotton.
Simple and complex carbs
You may have learned of carbohydrates which are simple and complex.
Monosaccharides and disaccharides are simple carbohydrates, and these are complex polysaccharides.
Simple carbohydrates: We make of just one or two molecules. They provide a strong energy source but the user will soon feel hungry again. Sources include white bread, sugar, and confectionery.
Complex carbohydrates: are composed of long sugar molecular chains. Wholegrains and foods are complex carbs that still have their fibre in them. They tend to fill you up for longer, and are considered healthier because we contain more vitamins, minerals and fibre. For example, fruits, vegetables, pulses and whole-meal pasta.
Carbohydrate-rich foods include bread, pasta, beans, potatoes, bran, rice, and cereals. Many foods that are rich in carbohydrates are high in starch content. For most species, including humans, carbohydrates are the most frequent source of energy.
If we had to, we could get all of our calories from the fats and proteins. One gram of carbohydrate contains around 4 kilocalories (kcal), equivalent to that of protein. There is about 9 kcal in one gram of fat.
Other essential functions, however, are carbohydrates:
- the brain needs carbohydrates, specifically glucose, because neurons cannot burn fat
- dietary fiber is made of polysaccharides that our bodies do not digest
The U.S. Dietary Guidelines 2015-2020 recommend that 45 to 65 percent of carbohydrate energy needs be obtained, and a maximum of 10 percent should come from simple carbohydrates, that is, glucose and simple sugars.
High-carb or low-carb diet?
Some “breakthroughs” appear every couple of decades and people are advised to “evitate all fats,” or “evitate carbs.”
Carbohydrates have been, and will continue to be, an essential part of any human dietary requirement.
Carbs and obesity
Some suggest that a high intake of carbohydrates is related to the global rise in obesity. To this question, however, a number of factors contribute:
- a reduction in physical activity
- a higher consumption of junk food
- a higher consumption of food additives, such as coloring, taste enhancers, and artificial emulsifiers
- fewer hours sleep each night
- a rise in living standards
Stress can be a factor, as well. One study found that the molecule neuropeptide Y (NPY) released by the body when stressed may “unlock” Y2 receptors in the fat cells of the body, stimulating the cells to grow in size and number.
As living standards and eating preferences shift, rapidly developing countries such as China, India, Brazil and Mexico are seeing a rise in obesity.
Their diets were more carb-heavy than they are now, when those populations were leaner. They also ate more fresh foods and less junk food, became more active physically, and slept longer at night.
What about diet foods?
Most advocates of high or low carb diets endorse marketed and refined items such as chocolate bars, powders, as weight-loss aids. Often these include colours, artificial sweeteners, emulsifiers and other additives, similar to junk foods.
When users of these products stay physically inactive, they may see some slight weight loss, but the weight will go back on when they leave the diet.
How can carbohydrates lead to diabetes?
The digestive system breaks down some of them into glucose when a person consumes carbohydrates. Such glucose reaches the blood and increases levels of blood sugar, or glucose. Beta-cells in the pancreas release insulin when blood glucose levels rise.
Insulin is a compound that removes blood sugar from our cells for energy or storage. As blood sugar is absorbed in the cells, blood sugar levels begin to drop.
When blood sugar levels drop below a certain point, the glucagon releases alpha cells in the pancreas. Glucagon is a hormone that makes glycogen, a sugar stored in the liver, release into the liver.
In short, insulin and glucagon in cells, especially the brain cells, help maintain regular levels of blood glucose. Insulin brings down high levels of blood glucose, while glucagon brings up levels when they’re too low.
When blood glucose levels rise too rapidly, too often, the cells will finally become dysfunctional and fail to respond adequately to instructions from insulin. Over time, the cells need to react to more insulin. This is what we call insulin resistance.
The beta cells in the pancreas will wear out after long years of producing high levels of insulin. Declines in insulin production. It may eventually stop altogether.
Effects of insulin resistance
Insulin resistance can lead to a wide range of health problems, including:
- hypertension, or high blood pressure
- high blood fat levels, or triglycerides
- low levels of “good” HDL cholesterol
- weight gain
- a range of chronic diseases
This is known as metabolic syndrome, and it is linked to type 2 diabetes.
Reducing the risk of metabolic syndrome
Long-term blood sugar control reduces the chances of developing metabolic syndrome.
Ways of doing this include:
- consuming natural carbohydrates
- good sleeping habits
- regular exercise
For fruit and vegetables, legumes, whole grains, and so on, the carbohydrates appear to reach the bloodstream slowly compared to the carbohydrates for processed food.
The carbohydrates in junk and processed foods and drinks can cause a person to feel hungry faster again, as they cause a rapid spike in the production of glucose and insulin. That is less likely to be done by natural foods containing carbohydrates.
The so-called Mediterranean diet is high in natural carbohydrates, with a small quantity of animal or fish protein.
Compared to the standard American diet this has a lower impact on insulin demands and associated health problems.
For good health carbohydrates are necessary. Those that come from raw, unprocessed foods like berries, vegetables, legumes, whole grains, and some cereals also contain essential vitamins, minerals, fibre, and main phytonutrients.
The glycemic index
Carbohydrates that rapidly increase blood sugar are said to be high on the glycemic index (GI), while those that have a more gentle effect on blood sugar levels have lower GI ranking.
Carbohydrates enter the bloodstream at varying rates as glucose.
- High-GI carbs enter the bloodstream quickly as glucose
- Low-GI carbs enter slowly, because they take longer to digest and break down
In the long term, low-GI diets are ideal for preserving health and body weight along with exercise and daily sleep.
Low GI carbohydrates are linked to:
- less weight gain
- better control of diabetes and blood sugar
- healthier blood cholesterol levels
- lower risk of heart disease
- better appetite control
- enhance physical endurance
Low GI diet
One aspect that improves a food’s GI score is the method of milling and grinding, which often leaves no more than starchy endosperm, or the seed or grain inner portion. Mostly, this is starch.
It also removes other nutrients including minerals, vitamins, and dietary fibers.
Eat more unrefined foods, such as: To adopt a low GI diet,
- oats, barley, or bran for breakfast, the less refined, the better
- wholegrain bread
- brown rice
- plenty of fresh fruit and vegetables
- fresh, whole fruit instead of juice
- whole grain pasta
- salads and raw vegetables
Junk foods, processed foods, and foods with too many additives should be avoided.
For health, we need carbohydrates but they have to be the right type of carbohydrates.
Following a well-balanced diet that includes unprocessed carbohydrates, and getting enough sleep and physical activity is more likely to result in good health and proper body weight than focusing on or eliminating a particular nutrient.