A deficiency in calcium can lead to a condition in which bones become brittle and fragile, a condition known as:

Calcium is the most abundant mineral in the human body and is critical for maintaining strong, dense bones. When the diet is chronically deficient in calcium, the body draws calcium from the bones to maintain blood calcium levels needed for nerve signalling, muscle contraction, and heart function. Over time, this depletes bone mineral density, making bones porous, brittle, and fragile - a condition known as osteoporosis. Osteoporosis significantly increases the risk of fractures, particularly in the hip, spine, and wrist.

The other conditions are caused by entirely different nutritional deficiencies:

• Goitre is an enlargement of the thyroid gland caused by iodine deficiency, not calcium deficiency.
• Beriberi results from a deficiency of Vitamin B1 (thiamine) and affects the nervous and cardiovascular systems.
• Pellagra is caused by a deficiency of Vitamin B3 (niacin) and is characterised by the "three Ds": dermatitis, diarrhoea, and dementia.

Exam tip: Link calcium to bones and osteoporosis; link iodine to thyroid and goitre; link B-vitamins to their specific deficiency diseases (B1 = beriberi, B3 = pellagra, B12 = anaemia).