What Are Micronutrients?
While macronutrients (carbohydrates, proteins, fats) are needed in large amounts, micronutrients — vitamins and minerals — are needed only in small quantities. Despite the tiny amounts required, they are absolutely essential for good health. A lack of a single vitamin or mineral can cause serious illness.
Vitamins
Vitamins are organic compounds — they contain carbon and are made by living organisms. The body cannot produce most vitamins in sufficient quantities, so we must get them from food.
Vitamin A (retinol) — Needed for eyesight (especially in dim light), healthy skin, and immune function. Sources: liver, oily fish, carrots, sweet potatoes. Deficiency causes night blindness.
Vitamin C (ascorbic acid) — Needed for making collagen (a structural protein in skin, blood vessels, and bones) and for immune function. Sources: citrus fruits, peppers, broccoli, kiwi. Deficiency causes scurvy — bleeding gums and slow wound healing.
Vitamin D (calciferol) — Needed for absorbing calcium and phosphorus, making strong bones and teeth. The body makes it when skin is exposed to sunlight. Sources: oily fish, egg yolk, fortified foods. Deficiency causes rickets in children (soft, bending bones).
Vitamin B group — A family of vitamins (B1–B12) involved in energy metabolism and nervous system function. Found in whole grains, meat, eggs, and leafy greens. Vitamin B12 is found almost exclusively in animal products — an important consideration for vegans.
Vitamin K — Needed for blood clotting. Sources: leafy green vegetables, vegetable oils.
Vitamins A, D, E, and K are fat-soluble — they are absorbed with fat and can be stored in the liver. Vitamin C and the B vitamins are water-soluble — they are not stored in the body and must be consumed regularly.
Minerals
Minerals are inorganic elements found in soil and water, absorbed by plants and passed on to animals that eat them. Key minerals include:
Calcium (Ca) — Essential for strong bones, teeth, muscle contraction, and nerve function. Sources: dairy products, leafy greens (kale, broccoli), sardines.
Iron (Fe) — A component of haemoglobin in red blood cells, enabling oxygen transport. Sources: red meat, spinach, lentils, fortified cereals. Deficiency causes anaemia (tiredness, pale skin, breathlessness).
Potassium (K) — Important for nerve and muscle function, and regulating blood pressure. Sources: bananas, potatoes, beans.
Iodine (I) — Required for making thyroid hormones which regulate metabolism. Sources: seafood, dairy, iodised salt.
Sodium (Na) — Regulates fluid balance and nerve function. Found in table salt. Too much increases the risk of high blood pressure.
Eating a wide variety of colourful fruits and vegetables is the simplest way to ensure you get a broad range of vitamins and minerals. Each colour tends to signal different phytonutrients and vitamins.
Deficiency Diseases
| Nutrient | Deficiency Disease | Main Symptom |
|---|---|---|
| Vitamin C | Scurvy | Bleeding gums, slow healing |
| Vitamin D | Rickets (children) / Osteomalacia (adults) | Soft, weak bones |
| Iron | Anaemia | Fatigue, breathlessness |
| Iodine | Goitre | Swollen thyroid gland in neck |
Real world: Vitamin D supplements in winter
In the UK and other northern countries, the NHS recommends that everyone take a vitamin D supplement from October to March, because sunlight at those latitudes is too weak to trigger enough vitamin D production in the skin. This became especially prominent during COVID-19 lockdowns, when people spent even less time outdoors. It's a direct real-world application of understanding that vitamin D comes partly from sunlight.
Real world: Iron deficiency anaemia in teenage girls
Iron deficiency anaemia is one of the most common nutritional deficiencies worldwide, particularly in teenage girls and women of childbearing age (due to monthly blood loss). Symptoms — fatigue, pale skin, difficulty concentrating — are often first noticed during school. Doctors test for anaemia with a blood test and treat it with iron-rich foods or supplements. Eating lentils, spinach, or fortified cereals, especially with vitamin C to aid iron absorption, is the dietary solution.
Real world: Fortified foods filling nutritional gaps
Many breakfast cereals, plant milks, and orange juices are fortified with vitamins and minerals — iron, calcium, vitamin D, vitamin B12. These additions are deliberate responses to known nutritional gaps in modern diets. For example, plant milks are fortified with calcium because they naturally contain far less than cow's milk. Checking whether a plant milk is fortified is a real application of micronutrient knowledge.
Where do you see this in real life? Check the vitamin and mineral content on the back of a cereal box — most list the percentage of Reference Nutrient Intake (RNI) per portion for vitamins and minerals. Looking at how much of your daily iron, calcium, and B vitamins a serving provides shows you how food choices affect your micronutrient intake in concrete numbers.
Practice Problems
answer="Vitamin D is needed for the absorption of calcium and phosphorus, which are essential for strong bones and teeth. A deficiency in children causes rickets — the bones become soft and may bend under the body's weight." />
Name one food source and one function for each of these minerals: iron and calcium.