Deficiency Disorders

Why deficiency disorders are guaranteed marks

A deficiency disorder is a disease caused by the lack of a particular nutrient — usually a vitamin or a mineral — in the diet over a period of time. Unlike infectious diseases caused by bacteria or viruses, these are non-communicable: they do not spread from person to person and are corrected simply by supplying the missing nutrient through diet or supplements. This makes them a clean, factual topic with one right answer per question.

The CDS examiners love this topic because the facts are finite and unambiguous. There are only a handful of vitamins and minerals, each tied to one or two classic diseases. A balanced diet supplies all of them; problems arise when one nutrient is consistently missing, as happens with poor or one-sided eating. Learn the table once and you can answer any phrasing — direct, match-the-following, or assertion-reason — without having to reason it out afresh each time.

It also overlaps with topics like nutrition, the digestive system and public health, so the same facts return in many forms across the General Knowledge paper. A few hours spent here pay off across the whole biology section.

Vitamins: the two families you must separate

Vitamins are organic compounds needed in small quantities to keep the body working normally. They are classified by what dissolves them:

• Fat-soluble vitamins: A, D, E and K. They dissolve in fats, can be stored in the liver and fatty tissue, and need not be eaten daily.
• Water-soluble vitamins: the B-complex group and vitamin C. They dissolve in water, are not stored (excess is passed in urine), and must be supplied regularly.

Vitamins were discovered because of the diseases their absence caused, so each one has a well-known deficiency disorder — exactly what the exam tests. The very word “vitamin” comes from “vital amine”, reflecting how essential these compounds are even in minute amounts.

One practical consequence of this split matters for the exam: because fat-soluble vitamins are stored, their deficiencies develop slowly and an excess (overdose) is possible. Water-soluble vitamins, being flushed out daily, rarely cause overdose but their deficiencies can appear quickly if intake stops. Keep this contrast handy for assertion-reason items.

Vitamin A and night blindness

Vitamin A (retinol) is essential for healthy vision, skin and the lining of internal organs. Its chemical name is retinol.

• Deficiency disease: night blindness (difficulty seeing in dim light) and, in severe cases, xerophthalmia (dryness of the cornea that can cause permanent blindness).
• Best sources: carrots, papaya, mango, green leafy vegetables, liver, milk and butter. The orange pigment beta-carotene in carrots is converted into vitamin A in the body.

Vitamin A also keeps the moist linings (mucous membranes) of the respiratory and digestive tracts healthy, so its deficiency lowers resistance to infection as well. That is why it is often part of government nutrition programmes for young children.

Vitamin D, rickets and the sunshine link

Vitamin D (calciferol) helps the body absorb calcium and phosphorus, which are needed to build strong bones and teeth. It is unique because the skin can make it when exposed to sunlight, earning it the name “sunshine vitamin”.

• Deficiency in children: rickets — soft, weak and bent (bow-shaped) bones.
• Deficiency in adults: osteomalacia — softening and weakening of the bones.
• Sources: sunlight, fish-liver oil, egg yolk, milk and butter.

Vitamin E and Vitamin K

Vitamin E (tocopherol) acts as an antioxidant and supports reproductive health and healthy skin. Its deficiency is rare but can cause reproductive problems and damage to red blood cells. Sources include vegetable oils, nuts, wheat germ and green vegetables.

Vitamin K is essential for the clotting of blood. The “K” comes from the German word Koagulation.

• Deficiency disease: failure of blood to clot, leading to excessive bleeding even from minor cuts.
• Sources: green leafy vegetables, cabbage, tomatoes and soybean oil.

The B-complex vitamins and their diseases

The water-soluble B-complex group is not a single vitamin but a family that works together, mainly to help the body release energy from food and keep the nervous system healthy. Each member has a distinct deficiency disease that the exam tests by name:

• Vitamin B₁ (thiamine): deficiency causes beri-beri — weakness of nerves and muscles.
• Vitamin B₂ (riboflavin): deficiency causes cracked lips, sore tongue and skin disorders (cheilosis).
• Vitamin B₃ (niacin): deficiency causes pellagra — the “3 Ds”: dermatitis, diarrhoea and dementia.
• Vitamin B₁₂ (cyanocobalamin): deficiency causes pernicious anaemia. B₁₂ notably contains the metal cobalt.

Vitamin C and scurvy

Vitamin C (ascorbic acid) is needed for healthy gums, teeth, skin and blood vessels, and it helps wounds heal. Because it is water-soluble and not stored, it must be eaten regularly.

• Deficiency disease: scurvy — bleeding and swollen gums, loose teeth, slow wound healing and weakness.
• Best sources: citrus fruits (orange, lemon, lime), amla (Indian gooseberry — one of the richest sources), guava, tomato and green chillies.

Historically, scurvy was the disease of long sea voyages, when sailors went months without fresh fruit. Once it was discovered that citrus fruit cured it, ships began carrying limes — a neat fact that sometimes appears in general-awareness questions. Vitamin C also helps the body absorb iron from food, linking it indirectly to the prevention of anaemia.

Minerals: iron, iodine, calcium and more

Minerals are inorganic nutrients the body needs for building tissues and running vital processes. Their deficiencies are equally examinable:

• Iron: needed to make haemoglobin, the oxygen-carrying pigment of blood. Deficiency causes anaemia — fatigue, pale skin and breathlessness. Sources: green leafy vegetables, jaggery, dates, liver.
• Iodine: needed by the thyroid gland to make its hormones. Deficiency causes goitre — swelling of the thyroid in the neck — and, in children, stunted physical and mental growth (cretinism). Sources: iodised salt, seafood.
• Calcium: needed for strong bones and teeth, muscle action and blood clotting. Deficiency weakens bones and teeth and can cause muscle cramps. Sources: milk, cheese, ragi, green vegetables.
• Phosphorus: works alongside calcium to build bones and teeth. Sources: milk, eggs, pulses and fish.

Notice that minerals, unlike vitamins, are inorganic — they are simple elements rather than carbon-based compounds. The body cannot manufacture them at all, so they must come entirely from the food we eat and the water we drink.

Protein and energy deficiencies

Not every deficiency disorder is about vitamins and minerals. Shortage of the macronutrient protein causes its own well-known diseases, common in undernourished children. Proteins are the body’s building blocks — they are needed for growth, for repairing worn-out tissues, and for making enzymes and hormones. When a growing child does not get enough, the effects are severe and visible:

• Kwashiorkor: caused by severe protein deficiency (even when calorie intake may be adequate). Signs include a swollen belly (oedema), stunted growth and patchy skin.
• Marasmus: caused by deficiency of both protein and calories (overall starvation). The child becomes extremely thin with wasted muscles.

Worked example: cracking a match-the-list question

Matching questions look long but are quick once you know the pairs. Work through them by eliminating the ones you are certain of first.

Notice you only needed two confident pairs to deduce the rest, because each remaining nutrient had only one possible match left. That is the speed advantage of memorising the master table: even if one or two pairs slip your mind, elimination fills the gap. In the actual exam, always read all four options of a matching question before marking, since the examiner sometimes swaps just one pair to trap the careless candidate.

Traps the exam sets for you

A few recurring confusions cost candidates easy marks every year:

• Mixing up rickets (D) and scurvy (C) — remember D for bones, C for gums.
• Thinking vitamin C deficiency causes anaemia — it is iron (a mineral) that causes anaemia.
• Assuming goitre is a vitamin deficiency — it is the mineral iodine.
• Confusing kwashiorkor and marasmus — protein-only versus protein-and-calorie.

Previous-year practice and quick recap

Memorise this table cold and you will pocket the deficiency-disorder questions in seconds, leaving more time for the harder mechanics and chemistry sections of the CDS Science paper.