The Human Fuel

Carbohydrates are the cheapest food humans can eat and although they contain the least energy amount among food categories
on weight basis, yet it is the main category that is responsible for overweight.


Carbohydrates resemble the main source (about 90%) of energy requirements of humans living away from extremely cold weather ( pole).
How much we take them? how the body deals with them? what is the impact of them on the body?. This is what we are going to discuss now.

Carbohydrates are present in many chemical forms:
-Mononmolecular form is either 5 or 6 carbon atoms.
-Dimolecular form which is a combined 2 monosaccharide (6 carbon atoms each).
-Oligosaccharide wich is formed of few combined monosaccharides.
-Polysaccharides( polymolecular chunks) of glucode.

Pentoses (5 carbon) are present in nature in bound forms, and oligosaccharides are of structural value (e.g.Antigens), but the disaccharides specially sucrose (sugar of commerce) which may make up as much as 40% of carbohygrate intake, and the polysaccharide starch, with glucose as the building unit of both, are abundant in nature and are relevant to energy production in humans.

Glucose is the most important molecule in carbohydrate metabolism.
-It can be catabolised (broken down gradually) in the cytoplasm to produce some energy as in muscle cell or red blood cell, and its catabolic products are oxidized in the cell energy house(mitochondria) to produce larger amounts of energy.

Glycogen is the storage form of carbohydrates in human body to meet rapid demand of glucose or enargy (fat is the other storage form).
The only human that can store glycogen in high amounts is the fetus before birth, however adult human can only store small amounts of it:

-Adult stores about 1/2 lb of glycogen in the liver which breaks it down during starvation to be completely depleted within 24 hours, the first thing the liver does after meals is to restore the normal glycogen store.
-Adult stores another small amount of glycogen in muscles which never give it up to be kept for their energy needs during exercise.

The human brain stores Glucose as is in the blood and the whole body is responisible for keeping a blood concentration within a narrow range, this is done primarily by the liver which can utilize glycerol (splitted from fat) and amino acids (from protein) to build up to 55 g glucose which accords precisely with the estimated energy requirements of the brain.

Blood glucose can only highly fluctuate in diseases:
1- High levels in diabetes mellitus. Glucose can react with body proteins and modify them contributing to Cataract and other long term complications of diabetes.
2- Low levels near to 0 in Cancer, producing a muscle waste and general weakness(cachexia). The ability of cancer cells to absorb huge amounts of glucose led some scientists in the former Soviet Union and in Germany to flood blood with glucose to kill the cancer cell by its own produced high acidity through cytoplasmic glycolysis of this glucose. It proved some success in some cases.


The surplus glucose is stored as FAT, the most efficient form as energy store on weight basis , man strategic energy resource which he never uses nor he needs, moreover, stored fat is a mechanical handicap and a health risk.

If humans think that their main fuel is produced by Sun (through plant) and that Sun is present all the time they are present on earth, they would have thought about not to keep energy stores!, but when it comes to cookies, candies, bakeries, pasta, and desserts, who cares?
Don’t you?.