A teenager follows a diet that contains very little iron and vitamin C. Explain why this diet may lead to health problems.

Iron is required for the synthesis of haemoglobin in red blood cells. A diet low in iron therefore reduces haemoglobin production, leading to anaemia and a decrease in oxygen transport throughout the body.
Vitamin C is essential for the synthesis of collagen, which is a major component of skin, gums and connective tissue. Without sufficient vitamin C, collagen formation is impaired, causing symptoms such as bleeding gums, poor wound healing and, in severe cases, scurvy.