Describe the functions, food sources and deficiency effects of key vitamins and minerals, and explain the role of water in the body

What this dot point is asking

You need to explain why nutrients needed in tiny quantities are still essential, give specific examples of vitamins and minerals with their functions and deficiency effects, and describe the roles of water.

Vitamins

Vitamins are organic compounds the body cannot make in sufficient amounts, so they must come from food. They are grouped by how they dissolve:

• Fat-soluble vitamins (A, D, E, K) dissolve in fat, are stored in the liver and fatty tissue, and can build up to toxic levels if taken in excess.
• Water-soluble vitamins (the B group and vitamin C) dissolve in water, are not stored well and any excess is excreted in urine, so a regular intake is needed.

Examples to know:

• Vitamin C supports the immune system and the formation of collagen for healthy skin, gums and blood vessels. Deficiency causes scurvy (bleeding gums, poor wound healing). Sources include citrus fruit and capsicum.
• Vitamin D helps the body absorb calcium for strong bones. Deficiency causes rickets in children. It is made in skin exposed to sunlight and found in oily fish and fortified foods.
• Vitamin A is needed for vision and healthy skin; deficiency causes night blindness.

Minerals

Minerals are inorganic elements with a wide range of structural and regulatory roles:

• Calcium builds bones and teeth and is needed for muscle contraction and nerve function. Long-term shortage contributes to osteoporosis (weak, brittle bones). Sources include dairy, leafy greens and fortified foods.
• Iron is part of haemoglobin, which carries oxygen in red blood cells. Deficiency causes anaemia (tiredness, pallor, breathlessness). Sources include red meat, legumes and leafy greens.
• Iodine is needed to make thyroid hormones that control metabolic rate; deficiency causes goitre (an enlarged thyroid). Sources include seafood and iodised salt.

Why small amounts still matter

Micronutrients often act as cofactors or are built into important molecules. A single iron atom sits at the centre of each haemoglobin group, and tiny amounts of iodine control the whole body's metabolism. Because they are not used as fuel, the amount needed is small, but the consequences of going without are specific and serious, which is why deficiency diseases such as scurvy, rickets and anaemia are named after particular missing nutrients.

Water

Water makes up roughly 60 percent of body mass and is the medium in which the body's chemistry takes place. Its roles include:

• acting as the solvent for reactions and for transporting nutrients and wastes in blood,
• regulating body temperature through sweating,
• lubricating joints and protecting tissues,
• removing wastes through urine.

Water balance is maintained by matching intake (drinks and food) with losses (urine, sweat, breath). Dehydration occurs when losses exceed intake, causing thirst, fatigue, headache and, if severe, organ failure. Water needs rise with heat and exercise.

In short, micronutrients and water are needed in small or non-energy quantities yet are indispensable: each vitamin and mineral has a specific job, and water is the medium that makes the body's reactions possible.