Blood is a miraculous fluid within our body. With millions of cells flowing in the blood system like stars in outer space, this fluid has a complex structure and composition that performs many vital tasks essential for our survival. For those who reflect, blood offers much to ponder.

Blood production begins around the second or third week in the mother’s womb within the vitellus, a sac that resembles the yolk of a bird's egg. This production then continues in the liver, spleen, thymus gland, and bone marrow, respectively. After birth, long bones take on this task, with spongy flat bones such as the skull, breastbone, vertebrae, and hip bones producing blood in adulthood.

In a healthy individual, blood volume is about 7% of body weight in adults and 8% in infants. For example, an adult weighing 70 kg (154 lb) has about 5 liters of blood, while a baby weighing 4 kg (8.8 lb) has about 0.32 liters of blood. Of the total blood volume, 55% consists of a fluid called plasma, while the remaining 45% is composed of cells. Plasma is 90–95% water, with the rest made up of fats, sugar, plasma proteins (albumin, globulin, fibrinogen), clotting factors, electrolytes (salts), and hormones. Blood cells, which constitute 45% of the blood, originate from the same stem cell and undergo specific differentiation processes. They then enter the bloodstream as three distinct cell types: erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (thrombocytes). Of these cells, the red blood cells—which give blood its red color—are directly related to the condition known as "anemia." A healthy adult has about 25 trillion blood cells (20–100 billion leukocytes/white blood cells, the rest are red blood cells). The average lifespan of a red blood cell is about 120 days. During these four months of life, they circulate the blood vessels in the body 300,000 times. There are about five million red blood cells in one cubic millimeter of blood. Erythrocytes that have completed their function and are worn out are recognized and destroyed by the cells (macrophages) responsible for destruction and are recycled in the bone marrow to be used in the production of new red blood cells [1].

The body maintains a balance between the rate of erythrocyte (red blood cell) destruction and production, ensuring a stable number of active erythrocytes in circulation. New red blood cells are continually produced and introduced into the circulatory system at an astonishing rate—2.4 million per second, or 208 billion per day.

Red blood cells are morphologically disc-shaped, with a diameter of 6.2–8.2 micrometers. If we line up each of our red blood cells side by side, their length would be 192,500 km (120,000 miles, which is about five times the length of the equator). If we stack the same cells on top of each other, the height of the resulting tower would be approximately 60,000 km. When the membranes of all cells are opened and spread out, the total surface area would be 3,100 m2 in men and 2,500 m2 in women. (one can compare this with a football field which is 7,500 m2). If we spread all the cells each touching another and without opening their membranes, they would cover an area of more than 1000 m2. The large surface area of red blood cells is a merciful design, as it allows for the rapid supply needed to meet the body’s high oxygen demand. Such a large surface divided into small units as many as 25 trillion cells enables rapid diffusion of a large amount of oxygen from the lungs to the red blood cells, and its transportation to other cells through blood vessels. The exchange time between blood plasma (where the cells are suspended) and the fluid surrounding the body’s cells is just three seconds. Such an extraordinary system of transportation and supply can only be the work of an infinite wisdom that knows every detail in its finest features.

Functions of blood

The vast majority of functions essential for our survival are carried out by blood. These include transporting vital substances—such as oxygen, glucose, amino acids, fatty acids, vitamins, and minerals—to the cells, and removing waste products like carbon dioxide, urea, and lactic acid produced through metabolism. Other essential tasks, such as preventing blood loss through coagulation, providing defense cells (antibodies) and their substances, transporting hormones, and regulating body temperature and water balance, are also crucial for the smooth operation of the body.

What is anemia?

Anemia is a blood disease that occurs as a result of insufficient number of red blood cells or their oxygen carrying capacity. The task of transporting oxygen in the blood is the task of a molecule called hemoglobin, which is found in red blood cells. Hemoglobin is a protein-like molecule that carries the oxygen it takes from the lungs to the tissues and the carbon dioxide it takes from the tissues to the lungs. It contains iron and gives the blood its red color. More than 98% of the oxygen in the body is loaded with hemoglobin, and 2% is dissolved in the blood plasma. There are approximately 270 million hemoglobin molecules in each red blood cell [2]. Anemia occurs if the amount of hemoglobin in a blood test is <13 g per deciliter (less than 13 grams) in men, <12 g in women, and <11 g in pregnant women. In children, these values vary according to age [3]. The number of patients with anemia in children and women of childbearing age in a society is accepted as an important public health indicator by the World Health Organization [4]. According to the World Health Organization, anemia affects

approximately one in four people worldwide, though its prevalence varies across countries and communities. The rates are 47.4% in preschool-aged children, 25.4% in school-aged children, 12.7% in men, 30.2% in women, 41.8% in pregnant women, and 23.9% in people aged 65 and over [5].

The causes of anemia can be grouped into three main categories: bleeding, reduced red blood cell production, and increased red blood cell destruction. There are many types of anemia, each with its own diagnosis and treatment methods, and some are genetically inherited. The first group of anemias arises from blood loss due to internal bleeding, often in the digestive tract, uterus, or bladder. If left unaddressed, such bleeding can lead to iron deficiency anemia over time. Therefore, it is important to examine these systems and organs closely in patients with unexplained iron deficiency anemia. A common example in this category is anemia caused by excessive menstrual bleeding, which should be carefully monitored in women and adolescent girls. The second group is called "aplastic anemias," in which blood cells are not produced in the bone marrow, and the third group is called "hemolytic anemias." In these types of anemia, erythrocytes lose their resistance due to intracellular or extracellular causes and break down easily. If the production of the bone marrow cannot compensate for these losses, severe, life-threatening anemia occurs in the acute or chronic stages [6]. Aplastic and hemolytic anemias, which can also be genetically inherited, are more serious and dangerous than the anemias mentioned in the first group. In these cases, depending on the severity of the disease, treatment methods such as splenectomy (removal of the spleen), lifelong blood transfusion or stem cell transplantation may be considered.

Iron deficiency anemia

This type of anemia occurs when the body does not have the amount of iron required for blood production. It is the most common type of anemia in all age groups worldwide. The element iron is found in the structure of hemoglobin and is essential for its production. Anemia occurs when the iron intake in the body is low. The oxygen amount transported to cells and tissues is not enough. As a result, various complaints and symptoms may begin to appear, including weakness, loss of appetite, difficulty concentrating, decreased mental function and physical stamina, dizziness, palpitations and shortness of breath that worsens with exertion, headache, fatigue, chest pain, tinnitus, cold hands and feet, pale skin, cravings for non-food substances like soil, ash, ice, or paper, pain and flattening of the tongue, nail deformities, and hair loss. In some patients with long-standing or mild anemia, these symptoms may go unnoticed. In such cases, anemia can be detected through a blood test [8].

Iron is essential for producing hemoglobin and is a crucial component for brain development in fetuses and newborns. It supports neurological development in infancy and early childhood and plays a key role in the formation of the myelin sheath—a substance that surrounds nerve cells. When myelin production is reduced, issues arise in nervous system development. If brain cells' iron needs are unmet, body, cognitive, and mental health issues can emerge in later life. This condition can also affect babies born to mothers with iron deficiency anemia during pregnancy [7, 8]. Due to its importance, nutrition guidelines recommend giving additional iron supplements to babies [9].

When we look at the data of the World Health Organization on the frequency of anemia, it is seen that there is an increase in anemia rates in infancy, adolescence, pregnancy and old age (65 years and older). The problems caused by anemia in the elderly are as serious as those in infancy and childhood. The most common causes of anemia in the elderly are chronic diseases (such as kidney, lung, heart, endocrine, intestinal diseases), iron deficiency, B12 and folic acid deficiency. In this age group, it was observed that there was a decrease in mental functions, and an acceleration in the development of dementia, physical injuries, confusion, behavioral disorders and mortality rates due to anemia [10, 11, 12].

For all age groups, the primary goal of treatment is to identify and address the underlying cause of iron deficiency. Treating iron deficiency anemia is generally straightforward and effective. Iron supplements can be administered orally or intravenously, depending on the need. A diet rich in iron-containing foods, such as red meat, eggs, and green leafy vegetables, is recommended, along with vitamin C sources (e.g., oranges, lemons, grapefruit, rosehip, vine leaves, fresh red and green peppers, parsley) to enhance iron absorption. Infants, adolescents, pregnant women and the elderly, who are at higher risk for iron deficiency anemia, should be closely monitored. In each case, the levels of substances such as vitamin B12, folic acid, and zinc in the body should be evaluated along with iron, and any deficiencies should be supplemented as needed. Since iron from animal sources is more bioavailable than from plant sources, vegetarians may require additional iron and vitamin B12 supplementation [13, 14].

“Atoms, especially those that come as a caravan of sustenance, travel with an astonishing order and wisdom through layers of existence and in many different modes. They pace along as if consciously without losing their direction and are strained through the four filters (digestive organs) in the body. In obedience to a law of generosity, they embark on red blood cells to come to the rescue of body parts and cells which are in need of that sustenance.” (Bediuzzaman, Thirtieth Word)

References

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2. D’Alessandro A ve ark. Red blood cell proteomics update: is there more to discover?, Blood Transfusion. 2017;15:182-187.

3. Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity. WHO, 2011.

4. Global Reference List of 100 Core Health Indicators (plus health-related SDGs). WHO, 2018.

5. de Benoist B et al., ed. Worldwide prevalence of anaemia 1993–2005. WHO Global Database on Anaemia Geneva, WHO, 2008.

6. Rodak BF. Hematology: Clinical Principles and Applications, Philadelphia: Saunders Elsevier, 2007.

7. Basu S et al. Effect of maternal iron deficiency anemia on fetal neural development. J Perinatol. 2018; 38:233–239.

8. Doom JR et al. Infant Iron Deficiency and Iron Supplementation Predict Adolescent Internalizing, Externalizing, and Social Problems. J Pediatr. 2018; 195:199–205.

9. WHO Guideline: Daily iron supplementation in infants and children. Geneva, 2016

10. Andro M ve ark. Anaemia and cognitive performances in the elderly: a systematic review. Eur J Neurol. 2013;20:1234-1240.

11. den Elzen WP et al. Effect of anemia and comorbidity on functional status and mortality in old age: results from the Leiden 85-plus study. CMAJ. 2009; 181:151–157.

12. Girelli D, Marchi G, Camaschella C. Anemia in the Elderly. Hemasphere. 2018; 2:e40.

13. Pawlak R, Berger J, BS, Hines I. Iron Status of Vegetarian Adults: A Review of Literature. Am J Lifestyle Med. 2016; 12:486–498.

14. Pawlak R. Is vitamin B12 deficiency a risk factor for cardiovascular disease in vegetarians? Am J Prev Med. 2015; 48:e11-e26