Anaemia in humans is most commonly caused by the deficiency of which mineral element?

Introduction / Context:
Anaemia is a common clinical condition characterized by a reduced number of red blood cells or a reduced amount of haemoglobin, which leads to decreased oxygen carrying capacity of the blood. Symptoms may include fatigue, weakness, pallor, and shortness of breath. One of the most common nutritional causes of anaemia worldwide is the deficiency of a particular mineral that is essential for haemoglobin synthesis. This question asks you to identify that key mineral.

Given Data / Assumptions:
• The options are cobalt, iron, sodium, and calcium. • The focus is on a mineral deficiency leading to anaemia. • Typical nutritional and haematological causes of anaemia are assumed.

Concept / Approach:
Haemoglobin, the oxygen carrying pigment in red blood cells, contains iron as an essential component of its haem group. Iron deficiency impairs haemoglobin synthesis and leads to microcytic, hypochromic anaemia. Cobalt is part of vitamin B12 and is involved in red cell production but cobalt deficiency is not the usual clinical term used. Sodium and calcium are important electrolytes for nerve conduction, muscle contraction, and bone health, but their deficiencies do not directly cause classic iron deficiency anaemia. Therefore, iron is the mineral whose deficiency most commonly results in anaemia.

Step-by-Step Solution:
Step 1: Recall that haemoglobin requires iron to bind oxygen effectively. Step 2: Understand that low dietary intake of iron, poor absorption, or chronic blood loss can lead to iron deficiency. Step 3: Recognize that iron deficiency is the most common nutritional cause of anaemia worldwide. Step 4: Identify that sodium and calcium are mainly associated with fluid balance, nerve function, and bone health, not with haemoglobin synthesis. Step 5: Choose iron as the mineral whose deficiency leads directly to anaemia.

Verification / Alternative check:
Public health programs aimed at reducing anaemia often focus on iron supplementation, iron rich diets, and fortification of foods with iron. Medical textbooks classify iron deficiency anaemia as a major type of nutritional anaemia. While vitamin B12 and folate deficiencies can cause other forms of anaemia, the question specifically asks about a mineral, and iron clearly fits this role. These points confirm iron as the correct answer.

Why Other Options Are Wrong:
Option A (Cobalt) is incorrect because although cobalt is a component of vitamin B12, cobalt deficiency is not usually discussed as a direct cause of anaemia in standard clinical practice. Option C (Sodium) is incorrect because sodium mainly regulates fluid balance and nerve function and is not a component of haemoglobin. Option D (Calcium) is incorrect because calcium is primarily associated with bones, teeth, blood clotting, and muscle function rather than red blood cell formation.

Common Pitfalls:
Some learners may be distracted by the presence of cobalt because of its link to vitamin B12 and its role in red cell production. However, the most widely known and common deficiency related to anaemia is iron deficiency. Always associate iron directly with haemoglobin and oxygen transport, and remember that iron deficiency anaemia is a very prevalent public health issue worldwide.

Final Answer:
Anaemia is most commonly caused by a deficiency of iron.