Sleeping Positions and their Effect on the Health of Internal Organs

Each new product we purchase has a user’s manual. Carefully read and used according to the recommendations, the life of the item will be long. The human body is no different as a user’s manual is required for good health. For example, the lifetime of the hip joint can be many decades if we take care to exercise and treat it properly. If not, calcification occurs and the duration of quality is shortened. Likewise, if we brush our teeth and follow the recommendations, decay can be restricted. Preventive medicine can reduce the likelihood of many diseases. 

Our Prophet ﷺ has stressed the importance of preventive medicine more than treatment medicine. There are many hadiths related to preventive medicine. Let’s take a look at the hadiths related to sleeping and sleeping positions:

Hadith Related to Sleeping Positions

It is understood from the hadiths pertaining to the sleeping position, our Prophet ﷺ would lay on his right hand under his cheek while lying on his right side.

Abu Hurayra said, “The Messenger of Allah, may Allah bless him and grant him peace, said, ‘When one of you goes to bed, he should undo the inside of his lower garment and dust the bed with it. He does not know what has come on his bed since he left it. He should lie down on his right side and say, ‘In Your Name I have laid down on my side. If You take my soul, then have mercy on it. If You release it, then preserve it in the manner in which You preserve the men of right action.’”

[Al-Adab Al-Mufrad Book 1 Hadith 6]

Al-Bara’ ibn ‘Azib said, “When the Prophet, may Allah bless him and grant him peace, went to bed, he laid down on his right side. Then he said, ‘O Allah, I have turned my face to You and I have surrendered myself to You and I have committed my back to You out of fear and desire for You. There is no place of safety or refuge from You except with You. I have believed in Your book which You revealed and Your Prophet whom You sent.’ He said, ‘Whoever says it at night and then dies, dies in fitra (natural state).’”

[Al-Adab Al-Mufrad Book 1 Hadith 7]

Whenever the Prophet (ﷺ) intended to go to bed, he would recite: “Bismika Allahumma amutu wa ahya (With Your name, O Allah, I die and I live). And when he woke up from his sleep, he would say: “Al-hamdu lil-lahil-ladhi ahyana ba’da ma amatana; wa ilaihi an-nushur (All the Praises are for Allah Who has made us alive after He made us die (sleep) and unto Him is the Resurrection).”

[Sahih al-Bukhari 6324]

Physiological Facts

Organs need more oxygen during exercise, and less at rest. The circulatory system plays a major role adjusting this need. During sleep, the heart rate slows down decreasing to 70 bpm while excess blood is stored in the veins.

Anatomically, the veins that bring blood to the heart entering from the right of the heart, and the artery (aorta) that distributes blood to the body exits from the left. Excess blood is stored in the veins, liver, and portal vein (veins that bring digested nutrients to the liver) so that the heart can draw less blood. To assist the storing process, sleeping on one’s right side will allow gravity to ease the process. 

Sleeping on the right side will be the most suitable position for storing blood and lowering the heart rate in response to the decreased oxygen need of the organs. Due to the dominance of the parasympathetic system during sleep, the heart rate and flow rate decrease. This is aided with the right lying position

The human heart is normally capable of pumping 13-15 liters of blood per minute. But at rest, it pumps 3-5 liters of blood. It is necessary to decrease the vein return to the right atrium of the heart to lessen the cardiac output during sleep. Storing is possible with the right lying position

Veins must remain open for the storing of blood. The negative pressure of the lungs serves this purpose. Without negative pressure, the main veins returning to the heart would be closed with the suction effect of the heart.

Sleeping on the right side helps negative pressure. The blood that is pooled in the veins along with gravity allows the veins to remain open.

Gravitational force has an effect on veins. For every 1 cm distance away from the right atrium, a 0.77 mm Hg pressure increases. While standing, the pressure in the leg veins is 85-90 mm Hg but lying down drops to 10 mm Hg reducing the amount of blood returned to the right atrium of the heart. This meets the needs of tissue during sleep. This reduction of blood returning to the right atrium is only possible by lying on our right side.

When we look at the anatomy of the portal vein, which carries nutrients to the liver, it follows a path from the mid-line of the body and enters the liver on the right. A person lying to the right, then, will facilitate the flow of the portal vein downstream. The direction of the lower venous vein from the liver to the stomach and spleen also flow to the right as an added advantage. 

Activity of the Nervous System

Two types of nerves, sympathetic and parasympathetic, regulate the functioning of the organs, their secretions, and the work of the vessels in them. During sleep, the parasympathetic system is often dominant. Sympathetic activity does not stop completely, but it decreases. Due to the parasympathetic activity, the work of the organs changes during the awakened state. Arterial pressure drops, pulse rate decreases, and skin vessels expand. The activity of the gastrointestinal system increases and there is complete relaxation of the body’s muscles.

In addition, secretion increases in the glands outside the pancreas and the enzyme secreting cells. The lung bronchi narrows and the contractile strength of the heart decreases. The coronary vessels of the heart expand, the urinary bladder relaxes at the entry point into the bladder, and pancreatic acetylcholine is released. When the amount of released water is low, pancreatic secretions are stored.

 So, when starting to sleep, a position on the right is important so that all affected organs and body systems help the parasympathetic effect. Let’s see how this is appropriate by examining the organs.

Anatomical Structures of Organs 

Lungs: There are anatomical differences between the right and left lung. The right lung bronchus is shorter, wider and closer to the straight line than to the left. The left bronchus is longer and narrower. The right bronchus is wider due to the larger right lung. While the left bronchus extends to the entrance to the lung, it passes under the main artery and has to pass a longer path than the right bronchus

When an unusual object goes into the trachea, it usually goes to the right lung. This shows that, as an anatomical structure, the right lung’s ability to breathe air is superior to the left lung. The large right bronchus shows that the right vent is more capable than the left.

Lung bronchi narrow because of the parasympathetic dominance in slow wave sleep. Since the basal metabolism of the body lowers, the oxygen need of the tissues decreases. When we lie to the right, not much air enters, since the opening of the right lung will be partially restricted. It receives enough oxygen for the body as a result of the narrowing of the bronchi and the fact that the right rib bone does not stretch too much. The right position for the lungs is good in terms of ease of entry of air into the right lung, contraction of the bronchus, meets the need for less oxygen and supports the parasympathetic activity.

Heart: The heart is located in a membrane bag called the pericardium between the right and left lungs. It is turned forward and left around its axis positioning the right ventricle forward of the left.

The angle of entry and exit of the dirty blood coming from the right atrium to the ventricle is 60°. The angle of the left ventricle in the entry and exit paths is approximately 10-15°.

When we lie on the right side, less blood will enter during the relaxation of the heart (diastol) with the blood deposited in the upper and lower main veins. Diastol (relaxation of the heart) will be extended to fill it with less blood. It will pump some blood into the lungs and leave some in the right ventricle. With normal circulation, the heart pumps blood that has entered the right atrium. It is suitable for the heart to work at low heart rate and to circulate less blood to organs during sleep. Therefore, lying to the right is suitable for the anatomy and physiology of the heart.

Parasympathetic activity increases in the heart vessels which allows them to expand and feed better. In patients with obstructive sleep apnea (obstructed breathing while sleeping) occurring in the upper respiratory tract, noradrenaline and sympathetic activity increases, and as a result, heart attacks can occur during sleep. Changing from parasympathetic activity to sympathetic activity while at sleep is a risky proposition.

Liver and Bile Flow: Most of the liver is located on the right with the gallbladder on its right. The liver is adjacent to the right lung through the diaphragm. It is the negative pressure in the lungs that helps the ligaments (mesentery), which keeps the liver in place. When we lie to the right, the narrowing of the bronchi reduces the negative pressure which helps keep the liver in its anatomical field with gravity.

 Parasympathetic activity during sleep increases the contraction of the gallbladder and biliary tract. The bile in the pouch passes into the biliary tract which opens to the 12 finger intestine with a soft slope to the right. The effect of gravity in a person lying to the right helps with parasympathetic activity and easier discharge of bile into the 12 finger intestine. Although peristaltic (alternating wavy contraction) movements of the biliary tract transport the bile to the right place, the right tilt will be helpful. It is a way of the Prophet Muhammad (peace and blessings be upon him) to lie down not immediately after a meal, but when the stomach is empty. This reclining coincides with the time when the bile is discharged the most and assists the emptying. 

Pancreas: The head is located to the right of the midline in the 12 finger bowel curve. Pancreatic secretion increases when nutrients come into the 12 finger intestine. Daily pancreatic secretion is around 1000 cc. However, parasympathetic activity increases secretion during sleep. If the 12 finger bowel is empty, the secretion stops. Apart from enzymes, there are bicarbonate ions in the secretion which neutralizes acidic kimusa(Semi-digested nutrients that pass from the stomach to the intestine.) or the acidic environment of the 12 finger intestine. This has a preventive effect on the formation of ulcers. When we look at the anatomy of the pancreas, the secretion channel flows from left to right. When we lie to the right, we support the flow using the effects of gravity.

Stomach: It is an organ that takes shape according to its position, whether it is full or empty. When the stomach is full, it expands in all directions, the shape and condition of the full stomach changes according to the state of the body. When we lie on your back with a full stomach, the stomach goes up. The top part, the fundus, expands and slides to the left.

The contents of the stomach fill the fundus when you lie on your back. The large protrusion of the stomach on the left pushes forward. The upper part is more expandable than the lower part which makes the shape of a horn. This is better seen on gastric film. In the patient lying to the left, the stomach slides to the left, the pylor (the passage channel from the stomach to the 12-intestine) comes forward, with a large protrusion of the stomach, the contents in it approach the fundus (top) and the stomach hangs down, leaving the 12-finger intestine up. Lyıng on your stomach creates a similar effect when the contents of the stomach slide to the top. When lying to the right, the full stomach shifts to the right of the mid-line, becomes like a gut, and the contents are positioned above the stomach outlet. The lower line of the stomach does not extend beyond the exit of the stomach. 

The empty stomach is located to the left of the mid-line and only the exit of the stomach is to the right. Its shape resembles the intestine. While empty, the front and rear walls are in contact with one another. The large upper part maintains its width and negative pressure prevents walls from sticking together. There is not much change in the empty stomach. The ideal gut-shaped stomach is achieved when hungry and lying down.

Small Intestines: Four hours after eating, the small intestine empties its contents into the large intestine. If someone eats around 6-8 pm, the nutrients are broken down in the 12 finger intestine and absorbed from the small intestine with the increased pulp transitioning to the large intestine between 10-11 pm.

For those who sleep with their stomach empty for 1-3 hours, the first two hours of sleep are called slow wave sleep. If one is lying to the right, the contents of the intestine are more easily transferred from the small intestine to the large intestine with the help of gravity.

A person given a test meal that was followed through the digestive system showed that the food was transferred from the stomach according to the amount and type of food. Liquid drinks leave the stomach immediately. Carbohydrates leave the stomach after one hour, protein from one and a half to two hours, while fatty foods become liquid slurry between two and a half to three hours.

A person eating dinner should pay attention to:

1- As the Prophet Muhammad ﷺ commanded, he should not go to bed before the night prayer and not lie down on a full stomach. 

2- Depending on the type of food and the amount, attention should be paid to the amount of time it takes to transit through the digestive system.

Reflexes: Of the many reflexes in a man, we must pay particular attention to the lying position which we call the tonic labyrinthine reflex. When the head is turned to the side, the deep neck sensory receptors are stimulated, the legs toward which the head is turned are stretched and the opposite side responds by bending the arm and leg joints to prevent strain.

When we lie down on our stomach, we have to turn our head to the side. In this position, tonic labyrinthine reflex is stimulated. Since the muscle contractions will continue in those lying by turning their neck to the side, there is no muscle rest.

When our Prophet ﷺ was lying on his right side, so as to relax the muscles, he also slept with his hand on his face to stretch his shoulder and elbow. If we do not put our hand under our face, the head will bend towards the shoulder, the head will be distorted and the anatomical position will be less than desirable as it will create curvature in the neck with the muscle on that side contracted. His most ideal position was also lying with his hips and knees bent. 

Considering the functions and anatomical structure of the organs, it is seen that the optimal position while sleeping should be on the right side. The second best position is to lie on your back because a person cannot sleep continuously in one position with regard to the stimulation of the pressure receptors.

Source: Dr. Arslan Mayda, “Yatış Pozisyonu”, Sızıntı, April 1999.