Carbohydrate
The body uses carbohydrates as fuel, especially in the muscles, heart and brain.
Carbohydrates exist as monosaccharides (having one sugar unit like glucose or fructose), disaccharides (having two sugar units like lactose), or polysaccharides (having more complex structures with many sugar units like starch or glycogen).
When glucose is not immediately needed it can be stored as glycogen in the liver and muscles. However, it may also be converted to fat and stored as such in the body.
Carbohydrate is not an essential nutrient. This may come as a surprise when you know that glucose is the fuel, which makes the muscles and the brain work!
If carbohydrate is not an essential nutrient, how can the brain and the muscles get the necessary amounts of glucose for their function if one eats little or no carbohydrate?
The answer is: from protein by the process of gluconeogenesis (“new formation of glucose”), which takes place – mainly in the liver – during periods of fasting, starvation, low-carbohydrate intake, or intense exercise.
Gluconeogenesis is a general metabolic process found in animals, plants, fungi, and bacteria. The process is energy-consuming and may be associated with ketosis (ketone bodies formation).
Sources
The modern Western diet contains a lot of carbohydrate in fruits, sweets, soft drinks, breads, pastas, beans, potatoes, bran, rice, and cereals.
Below is a list of foods having the highest content of carbohydrates in g per 100 grams of the food.
The list is made using ECstep’s Personal Nutrition Data Program. Commercial brand products are not included in this list.
A problem with many carbohydrates is that they are refined like in white bread, pasta, and polished rice. When eaten these carbohydrates lead to a rapid rise in blood glucose. This stimulates release of insulin, which decreases blood glucose. Thus the blood sugar fluctuates a lot between high and low and this is bad for your health.
You should also be aware that humans have only eaten grains for a very short time in evolutionary perspective. We are not well adapted genetically to grains.
Coeliac disease is caused by allergy to gluten – a protein in wheat, rye, and barley. The full-blown coeliac disease develops in about 1% of people. The symptoms include diarrhea, bloating, tiredness, and weight loss.
The healthiest sources of carbohydrates are fruits, beans, green leaves, and some roots.
Daily intake
Carbohydrates are not necessary building blocks for other molecules, and the body can obtain all its energy from protein and fat. Thus you could leave out carbohydrate from you diet provided you get enough protein, fat including essential fatty acids, vitamins, minerals and water. Your blood glucose would be much more even on such a diet.
If you need the extra fuel that carbohydrate can provide, the best sources are the slowly absorbed complex forms found in fruits, beans, green leaves, some roots, brown rice, and whole grains – if you can tolerate them. You should avoid sugar and refined carbohydrates as much as possible.
Deficiency
Since carbohydrate is not necessary, you can have a good health without carbohydrate provided you get enough protein, fat including essential fatty acids, vitamins, minerals and water.
Excess
If you eat large amounts of carbohydrate, your blood glucose will increase. This will stimulate insulin release, which will promote transport of glucose to the liver and muscles. There it can be stored as glycogen, which serves as carbohydrate storage of limited size. Glucose can be released from this storage when needed.
When immediate energy needs are met and the glycogen stores are full, the excess glucose is transformed in the liver into fatty acids, which go with the blood to the fat or adipose tissues, where they combine with glycerol to form triglycerides for storage. In this way the body can store enormous amounts of energy as fat in the adipose tissues.
This ability to spare extra energy from carbohydrate in fat stores seems to have been favored in the evolution as an advantage for survival in periods of food scarcity.
With the present abundance of refined carbohydrate in the food of the Western world this ability to transform excess carbohydrate to fat is more of a disadvantage and probably a most important mechanism behind the developing epidemic of obesity. Here is information about losing weight.
The fat stores can be used to generate energy by using the fatty acids as fuel. However, the fatty acids cannot be transformed back to glucose or other carbohydrates.
There is a lot of energy bound in fat, namely 9 Kcal per gram. This caloric energy is more than twice that of carbohydrate and protein, both having a caloric energy of only 4 Kcal per gram. Fat is a concentrated energy source.
