Compared to the life of Man on earth, consumption of bread as the main source of food for the majority of people throughout the world is only a recent event, a time span of six thousands years, that is since the first group of humans settled down and discovered agriculture. Before that Man subsisted mainly on meat and fruit (including nuts and vegetable roots). Now biologically there are three main groups of molecules that make up the main constituent part of Man's diet: proteins, fats and carbohydrates. And the latter is what wheat and rice (another major source of food for a large number of the world's population) mainly consists of. But our bodies is not genetically prepared (think broadly in terms of evolutionary changes which usually take thousands of years to actually enter our genetic pool) to deal with carbohydrates in such high quantities. Fruits and vegetables (as what our ancestors ate beside meat) do not contain that much carbohydrate. And when they do they usually contain the enzyme required for their break down. So the question is what does our body do with this extra or unusual amount of carbohydrates?
Digestion of carbohydrates start in the mouth with the enzyme (ptyalin or alpha - amylase) found in the saliva. And as the food remains in the mouth only for a short period of time, only 3-5% of all the carbohydrates eaten is broken down before it is swallowed. The rest is digested, that is broken down, in the small intestine by pancreatic amylase. The end result of carbohydrates break down consists mainly of glucose which is then absorbed through the intermediacy of the hormone, insulin and by an energy consuming process. The final step in carbohydrates metabolism occurs in the cell where glucose in the presence of oxygen is broken down to produce energy in the form of ATP molecules.
Usually, the more carbohydrates in the diet the more insulin is required for their absorption. It has been shown that after the consumption of food rich in carbohydrates, the amount of insulin secreted is higher than that needed for glucose absorption. Thereby the extra insulin in the blood gives rise to a state called hypoglycemia or low blood sugar and false hunger. As the result, one craves for sweet things (cakes, for example), that in turn leads to insulin secretion. In this way a vicious circle is formed naturally leading to obesity.
On the other hand, high levels of insulin increases the rate of degradation of an important neurotransmitter called Serotonin. Serotonin deficiency gives rise to symptoms such as disturbed sleep and depression that can produce a craving for sugar. Increased intake of sugar together with general fatigue produced as the result of disturbed sleep gives rise to another vicious circle. That is why drugs that inhibit serotonin breakdown may prove beneficial here, for as it was stated before sufficient levels of serotonin produces deep restful sleep that can then break the corresponding vicious circle explained above.
The last thing to add here in relation to increased amount of insulin secretion is that high levels of this molecule in blood leads to sodium and water retention, that in turn leads to edema of limbs and in severe cases general edema.
On the other hand, high amounts of glucose in the blood inhibit the break down of fats (the second major food molecules) as a source of production of energy. This is called 'fat sparing effect of carbohydrates.' In the presence of excess carbohydrates, fats are synthesized instead of being degraded. As the result they are stored in the body leading to obesity again.
As it was mentioned above carbohydrates are broken down mainly by the enzyme amylase and consumption of high amounts of carbohydrates naturally leads to amylase deficiency, since this enzyme would be used up by the body at a tremendous rate. In addition to its role in carbohydrates' digestion, amylase is involved in anti-inflammatory reactions, so amylase deficiency may lead to all types of skin problems and aggravation of asthma and emphysema. Other symptoms observed in case of amylase deficiency include general fatigue, cold hands and feet, depression and mood swings.
Usually, in addition to the final products of digestion of carbohydrates (i.e. glucose, fructose, galactose, and in one word monosaccharides) a small amount of disaccharides too get into the blood. High amounts of carbohydrates would naturally lead to higher amount of disaccharides entering the blood which would in turn increase blood concentration and thus its osmotic pressure. As a result, blood circulation slows down or blood flows more sluggishly leading to further dysfunctions, including resorption of calcium from the bones that in older people can act as an additional factor giving rise to the condition called osteoporosis (or brittle bones).
Finally, the carbohydrates that totally escape degradation should be transformed to feces. This process needs a high expenditure of energy which in turn leads to oxygen and ATP (energy molecule) deficiency. Consequently food metabolism in general is affected.
>From what was said, should we still eat so much bread or other food rich in carbohydrates, especially after the onset of the process of aging?
This really depends on the amount of our physical activity. For example, although the main food of farmers or the majority of the poor people of the world is starch (whether in the form of bread, or rice or potatoes and the like), overweight is rarely seen among them. This is due to their high strenuous physical activity. In addition, as undigested carbohydrates absorb water, they produce a great volume that keeps stomach extended for a longer time. As the result the person will not feel hungry for a relatively longer time.
However, as the amount of physical activity is comparatively much lower among the city dwellers they should watch their diet much more carefully and avoid carbohydrates intake as much as possible. This is especially true once the active years of youth are over and the process of aging starts. Other nutritional advices here include: cutting down the amount of food intake in general and replacing carbohydrates containing food with fruit, vegetables and nuts, that have been the major source of human food from the time immemorial. Once again, let us remember that from the perspective of evolution, six or seven thousands years is not really that long to introduce the genetic changes required for digestion and metabolism of any new source of food. This includes all the seemingly 'benign' or harmless chemical substances we consume whether in the form of food additives or drugs as well.
"Things sweet to taste prove in digestion sour"
Shakespeare (from "The Winter's Tale, III:2)
... Payvand News - 6/16/03 ... --