With this act, the holy Pole meant, “Whenever your son’s spirit prevails over his body, and his heart over his carnal soul, and his intellect over his stomach, and he demands pleasure for the sake of thankfulness, then he can eat delicious things.” (Said Nursi, Nineteenth Gleam, 3rd point.)

I too witnessed a similar incident thirty years ago. With a large group of friends from university I was invited to visit a well-known scholar for whom I had a deep respect. We had the opportunity to attend a dinner with him and among the food served were some delicious cherries. My inner voice said, “If I sit near him, I will not be comfortable enough to eat as many of those cherries as I like.” This was exactly what happened. While I was thinking about how to get a chance to eat more of the cherries, that respected person took one of the cherries, excused himself, and left the table. I still cannot forget how ashamed I was of my thoughts at that time.

As a result of the story of Abdul-Qadir Jilani and my own experience, I started to ponder the activities that function so well in the human body. In medicine, the dynamic balance that entirely governs the body during eating, drinking and digestion is known as homeostasis. The most crucial body fluid in this balance is the blood. All the agents in the blood have a fixed quantity, a fixed measure and are supplied at a constant rate. Blood pressure is stabilized according to the characteristics of each vein. For instance, the average blood pressure of large arteries is about 100 mmHg. If the pressure exceeds this figure, then the result is hypertension. Hypertension can lead to cerebral hemorrhages, paralysis, renal failure, cardiac expansion, cardiac failure and heart attacks, all of which can result in death. As for hypotension, this is when the flow of the blood to the organs, mainly the brain, lessens. Another example of the importance of maintaining balance is that the agents which are responsible for maintaining the concentration of sugar in the blood (glycemia) must be kept at a suitable balance. If the ratio of the blood sugar (glycemia) rises, the person may go into a sugar coma, which is life threatening. However, if the ratio of blood sugar drops, the organs, in particular the brain, are deprived of energy. A hypoglycemia coma (when blood sugar is too low) is even more dangerous for the brain than hyperglycemia (when blood sugar is too high). The concentration of sodium, potassium, chlorine, calcium and fatty acids present in the blood, like sugar, are kept in a dynamic balance. If this concentration is upset, the result may be disease or even death. The Owner of Absolute Will and Infinite Mercy keeps all these in balance thanks to the marvelous mechanisms that He has placed in our bodies. However, we are free as far as actions like eating and drinking are concerned, for we are granted the willpower to choose our actions.

Balance in nourishment

One of the most often discussed medical subjects in recent years is obesity. This is an important health problem that poses a threat to life, and it is related to diabetes, hardening of the arteries (arteriosclerosis), fatty liver, cirrhosis, cardiac failure and heart failure. Apart from using one’s own will power and eating less, doctors have presented other harmless ways that are appropriate to human nature to treat obesity. Being overweight constrains the ability of a person to move (exercise) and this inactivity, in turn, leads to more and more weight gain. God has enabled us to seek nourishment wherever we like, within certain parameters. Naturally, our stomach has a certain capacity and when this capacity is met, we feel full and do not need to eat any more. Yet, even though we feel full and should not eat, as this is what is necessary for the health of our body, we are overcome by our lower self and tend to overeat extravagantly. The problem of obesity seems to be greater in developed countries.

Our Creator has not put any restrictions on the absorption of food into the blood. All the food we eat is taken into the intestines so that the nutrients can pass into the bloodstream. If the dynamic balance (homeostasis) were to be maintained here as well then the body would take as much as it needed and the surplus of food would be evacuated from the body without going into the blood; as a result, obesity would not be a concern, however much a person might eat. But by allowing all the food we eat to pass into the bloodstream, the Absolute Ruler has set a test for us, challenging our wills and warning us about self-control.

Most of the activity during digestion and absorption takes place in the small intestine. Our small intestine is a duct which consists of three parts, namely the duodenum, jejunum and ileum, each having different functions and structures. The length of the intestine is 3–4 meters, and it measures 2–4 centimeters in diameter, varying according to the position in the body. The area of the inner surface of this cylindrical structure is 1,600 cm2 (0.16m2) at its maximum. The inner perimeter of the intestine is not like a flat tube, but rather it has folds, each measuring about 8 millimeters, that stretch over the inner parts of the canal. These folds allow the absorption surface to be increased about threefold. If the inner surface of this structure were flat, the absorption capacity of the small intestine would not be more than 1/600 of its present capacity. The surface of these folds is also not flat, but covered with protrusions called villi that are shaped like a finger; these stretch into the vacuum of the canal by about 1 millimeter. There are between 20 and 40 villi to every square centimeter on the surface of the intestine. These villi allow for there to be a tenfold increase in surface absorption. The surface of the villi has cylindrical cells that are arranged in a single row and these help in absorption. The surface of these cells has extensions that are quite thin and dense, known as microvilli, or epithelial cells. Thanks to these cells with a brush border surface, the absorption surface can increase by about twenty times. Thus, although the surface area of a flat canal of the same size should be approximately 3,300 cm2, thanks to surface folds, villi and bushy edges, the total absorption surface of the small intestine increases to 2 million cm2 (200 m2). Moreover, some research has suggested that the total increase could be even greater (about 1,000 times as much). Normally, 100 grams of fat, 50–100 grams of amino acid, 50–100 grams of iodine, and 7–8 liters of water (consisting mostly of fluids produced within the body) are absorbed by the intestines daily. Furthermore, if one eats or drinks too much, the maximum capacity of the system allows the absorption of several kilograms of carbohydrates, a half to one kilogram of fat, a half to one kilogram of protein and twenty liters of water per day. Our intestines have been created with the capacity to transfer all this food into the bloodstream. If we do not control our eating, this capacity is abused and we can face conditions like obesity.

In this life, one of whose tests is in our body, and in which we are required to strive hard using our willpower, there is no limit to the absorption of foods that have high calories (lipid, carbohydrate, and protein), and this can lead to being overweight, as mentioned above. However, in the absorption of minerals, which are not normally considered as making up the basic components of nourishment, but which are of the utmost importance for the human body (in all the operations of the nerves, muscles, bones and in the balance of all the electrolytes), the rules of dynamic balance occur in our intestines, regardless of our will, by the help and mercy of God. For instance, hemoglobin, which is found in the red blood cells (giving the blood its red color) and is charged with the task of transporting oxygen, contains iron. When there is surplus iron in the body, hemosiderosis occurs, which leads to the destruction of organs such as the liver and the pancreas, or cardiac failure. If there is an iron deficiency, then a person suffers from anemia. It is for this reason that a quite sensitive iron-absorption balance exists in our intestines. Here, it is evident without question that there is Divine Aid and Mercy. The same mechanism works for substances like calcium.

Prophet Muhammad’s, peace be upon him, advice to stop eating before feeling full is a significant measure against obesity, for it eliminates “false” appetite. This has a psychological truth, for the brain responds to the feel of fullness a short time after eating. In fact, we all know by experience that we actually feel full a short while (fifteen–twenty minutes) after we stop eating even if it is a small meal.

To conclude, the Almighty One warns us against extravagance and orders us to use our willpower. At this point, we can see how important a role the blessing of religious belief and the training of the soul and the will play in eating habits. Likewise, the principles of Islam, which is in perfect keeping with human nature, are crucial for the well-being of the community as a whole; charitable alms and fasting, which urge us to help and think about those with less, are obligatory and all kinds of charity and good deeds are encouraged. In Islam extravagance is prevented, not only in eating and drinking.

Omer Arifagaoglu is a professor of medicine in Turkey.

Dear Peter, in order for you to understand me better, keep in mind a basic principle about the functioning of living organisms-they all depend on energy use. If no energy enters a living system, then no metabolic activity, no life function can be carried out. Think about a car without fuel. No matter how great the car is, it simply won’t work without any fuel in the tank. The human body is no different. Plants and animal products which people consume as food provide the body with fuel. However, you cannot make use of the energy in nutrients in the form in which you take them in. They need to undergo a process so that they become usable fuel for us, like crude oil being refined into gasoline to make a car work. This is roughly what my duty is. Without my functioning, you would be devoid of the energy to move a finger, and eventually die. Do you understand now how important a set of pipes I am? You just think that I look like a soft and hollow canal and misjudge me as simple. Well, I know that I don’t have such complex parts as the heart, lungs, and kidneys, but I’m created as a perfect work of art in plain design.

Although the hoses you use for watering your garden wear out and break in a relatively short time, my walls made of four layers keep functioning through a lifetime without any holes unless I contract a disease like cancer. My outer layer consists of a durable connective tissue, the next one consists of two sets-one horizontally and one vertically laid-of straight muscles, the next layer under that consists of glands spread in a soft connective tissue, and the innermost layer is the epithelial mucosa where the actual absorption takes place.

Now, let’s come to how I achieve digestion, one of your body’s vital activities. Actually, there is no place for me to take any pride in it; I’m just doing as I am ordered. Anyway, the complex processes occurring within my simple-looking walls are just fascinating! Every one of my cells producing the particular enzymes to break up each nutrient is like a separate factory. Some of these enzymes break proteins into different levels of peptides, some break the peptides into amino acids, some break fats into fat acids and glycerin, whereas some break carbohydrates down into glucose. All of these particular enzymes have their sub-branches within themselves. For example the enzymes breaking down fructose (fruit sugar), lactose (milk sugar), and starch are all different. In order for the enzymes to be effective, my inside needs to have the right pH level; the enzymes work in very sensitive conditions. To give you an idea, the enzymes in the stomach-which happens to be the second station the nutrients are destined for before they come to me-work in an acidic environment (pH: 2.5–3). In my case however, basic fluids are secreted and this strong acidity is neutralized for my enzymes to work.

My overall length is around 8.5 meters from the first entrance at the stomach to the last exit. The small intestine is nearly 7 meters long and the remaining 1.5-meter section is the large intestine. Although the small intestine is the longest section of the digestive tract, it is still called small since it is smaller in diameter than the large intestine.

The small intestine is also divided into three sections. The very short (25–30cm) and relatively thicker part right after the stomach is the duodenum. Bile-which works like detergent and facilitates breaking up fats-produced by the liver and digestive enzymes from the pancreas enter the duodenum. Thus, the nutrients are digested one step further and pass on to the second section (jejunum) and then to the third (ileum). You cannot easily tell apart these final two sections. As blood circulation is more intense in the second section, this section is more reddish and the contractions here are faster and stronger. The third section is narrower and has thinner walls. The blood circulation here is relatively lower and the movements are more limited. The thin membrane of connective tissue (mesentery) around me which attaches me to the abdomen wall and prevents me from knotting up is relatively fatty in this third section.

My most vital parts are the villi-tiny nipples covering the curly surface of my inner wall like a carpet. Shaped like the fingers of a glove, villi yield an enormously large inner surface. They contain a net of capillaries and lymph canals. In addition to the glands secreting the enzymes to break down nutrients, the secretion of certain glands protects me against the destructive effect of the stomach acid. Some cells secrete mucus for lubrication and protection of the passing nutrients. As some cells of the villi secrete digestive enzymes, some of my cells absorb the nutrients broken down until the final phase and pass them to the bloodstream.

Peter, how can some guys mistake such a splendid mechanism as a work of unconscious nature? What I’m telling you about is a manifestation of such great knowledge and might that it leaves you spellbound. I know the characteristics of foods, I know about the other organs’ needs, I adjust various enzymes and an absorption system, I fit them in a limited space… In addition, I do all these in the most ideal way, without any waste or flaw! C’mon Peter, can all these happen by themselves? Now, if I were to start telling everyone about the absorption mechanism in detail, they would probably see those cells as divine beings! The One who assigned special carrier molecules and a system for every nutrient molecule, has placed two transfer systems as blood and lymph pathways in every single one of those millions of villi! The blood pathway passes amino acids, water and salts into the blood directly, whereas the lymphatic pathway absorbs fats to pass them to the blood indirectly. After absorption, the nutrients become a property of the body and they are carried in the bloodstream to all the cells waiting for them in need.

Well, what about the waste then? Since everything you eat is not beneficial and usable, and some things are even toxic, they should be disposed of as soon as possible. The unabsorbed remnants are still too watery to be disposed of; sending them away as they are will be a waste of water and minerals. But don’t worry, everything is perfectly planned! Now the large intestine comes on duty. In this 1.5-meter section, the water of the waste and certain minerals are absorbed, and the waste solidifies. The large intestine is also divided into three sub-sections. The pouch connected to the junction of the small and large intestines is named the cecum and there’s the appendix at its end. This end sometimes festers and you have to have it removed in an appendectomy. Now, there’s this made-up story that the appendix was once longer since your ancestors only ate plants, that it has evolved into a shorter form for I now eat more meat, so on and so forth… Bah! Nothing is created in vain, Peter. If it didn’t have a duty, it simply wouldn’t be created. Only after some time did it dawn on them, after researchers proved that it is so necessary, that as a lymphoid organ, rich in blood vessels, it produces antibodies to fight the germs which somehow make their way into me.

The rest of the large intestine is the colon and the rectum. The mucosa covering my inner surface is rather smooth. It secretes mucus to facilitate the removal of waste. In addition, useful bacteria are made to work in abundance in the large intestine for your needs. These bacteria synthesize the group B vitamins like B12, thiamin, and riboflavin, along with vitamin K. You see how all the processes are carried out so splendidly? If it weren’t for vitamin K, your blood would fail to coagulate, and the slightest injury to your blood vessels would kill you. Could you ever have imagined that what looks to you like a sewage canal could produce vitamins of vital significance? Your Creator has infinite wisdom.

Peter, now you may wonder how the acts of this organ which resembles a long hose are regulated, how the nutrients inside are propelled, and then thrown out. To put it briefly, the “willful” part of your brain does not even know about it. Indeed, if it knew, it would be constantly busy with me and unable to do anything else.

Under the control of the autonomous nervous system, the straight muscles of my walls gradually contract in waves-this is squeezing act is called peristalsis. The nerve fibers connected to me fall into two basic categories-sympathetic and parasympathetic. As the sympathetic fibers pressure me to slow down, parasympathetic fibers stimulate me to act. Thus, I try to keep a balanced functioning between these two opposite effects. When the waste material I propel this way assumes a state to be disposed of, it reaches the rectum, and when the walls here strain, I make a natural call to you that I need to get rid of garbage. This is the step where your will has a partial interference.

Colon cancer, which troubles many people today, appears in this final section. The major reason is consuming too much meat and fatty foods, lack of movement, and leading a stressful life. When these are combined, I fail to function properly. If you want to help me at that, you should consume fiber-rich foods such as fruit and vegetables, and also lead a peaceful life. My web of nerves is amazingly rich and complex. Therefore, I am sensitive to nervous changes. If you feel down or sad, and if you suffer too much stress, I begin to go into spasms. Then I fail to dispose of waste, the toxic material inside me begins to damage my inner walls and eventually increases your cancer risk. Therefore, you’d better take up the habit of a glass of warm water when you get up in the morning, and try to have regular meals at the same times of the day. Most importantly, always have fresh green vegetables on your table, reduce meat intake… and it would be great if you could afford to consume olive oil rather than any other.

Hey, wait! I was about to forget the most important point. If you don’t have any peace of mind, all of these will be useless. This doesn’t mean that you will never worry; after all, this world is a testing ground and you are a human being like anyone else. However, if you give in to troubles and get overcome by feelings like panic, fatigue, and hopelessness, then my functioning will be upset. So, troubles faced with active patience and effort without giving up hope do not harm me much.

Peter, I do not wish you to wait until you see colon cancer patients disposing of waste through a hole in their belly into a plastic bag before you feel grateful for the blessings you enjoy. Actually, maybe I have told you at most a tenth of what I know about myself. Anyway, I think even this much will give you an idea of what a work of art I am. Thanks for listening to me, Peter!

Irfan Yilmaz is a professor of biology at Dokuz Eylül University, Izmir, Turkey.