Human Health: Nutrition, Diseases and Immunity

Prerequisites: Physics and Chemistry in Daily Life · Biotechnology and Health

The Hook: The Last Case of Polio

The Core Concept

1. Nutrition — what the body needs

What it is. The body needs carbohydrates and fats (energy), proteins (growth and repair), vitamins and minerals (regulating body processes), water and dietary fibre.

How it works. Vitamins are needed in small amounts and mostly cannot be made by the body, so they must come from food. Fat-soluble vitamins (A, D, E, K) are stored in the body’s fat and liver; water-soluble vitamins (B group and C) are not stored for long, so they must be eaten regularly. Two exceptions: the skin makes vitamin D in sunlight, and gut bacteria make some vitamin K.

Protein-energy malnutrition: kwashiorkor (protein deficiency — swollen belly and limbs) and marasmus (deficiency of both protein and calories — severe wasting).

India’s status. NFHS-5 (2019–21) reported that 35.5% of children under five were stunted and 57.0% of women aged 15–49 were anaemic. India faces a double burden of malnutrition — undernutrition and micronutrient deficiency alongside rising overweight and obesity. Responses include POSHAN Abhiyaan (launched 2018), double-fortified salt (iodine and iron), and fortified rice in public food schemes.

2. Diseases — what causes them and how they spread

Non-communicable diseases — diabetes, hypertension, heart disease, cancers, chronic lung disease — are now the leading causes of death in India. Diabetes results from insufficient insulin (made by the beta cells of the islets of Langerhans in the pancreas) or the body’s resistance to it.

3. Immunity — how the body defends itself

How it works (in one paragraph). The body’s first defences are innate — skin, mucus, stomach acid, fever, and white blood cells that attack any invader. If these fail, acquired (adaptive) immunity takes over: B-lymphocytes produce antibodies that lock onto a specific antigen, and T-lymphocytes kill infected cells and coordinate the response. Crucially, some of these cells become memory cells, so a second encounter with the same pathogen triggers a faster, stronger response. A vaccine exploits this memory by presenting a harmless form of the antigen.

• HIV attacks helper T-cells (CD4 cells), weakening the whole immune system — hence opportunistic infections in AIDS.
• Herd immunity — when enough people are immune, transmission falls and even the unvaccinated are protected.
• Allergies are an over-reaction of the immune system to harmless substances; autoimmune diseases occur when it attacks the body’s own cells.

4. Antibiotics and antimicrobial resistance (AMR)

Antibiotics kill or stop the growth of bacteria; they have no effect on viruses. Alexander Fleming discovered penicillin in 1928. AMR arises when microbes evolve to survive drugs — accelerated by unnecessary prescriptions, incomplete courses, over-the-counter sales, and antibiotic use in livestock and poultry. India launched a National Action Plan on AMR in 2017 and a “Red Line” campaign (2016) marking prescription-only antibiotic packs with a red vertical line.

5. Blood groups

The ABO system was discovered by Karl Landsteiner. Blood group depends on antigens on red blood cells and antibodies in plasma.

The Rh factor adds a positive or negative sign. An Rh-negative mother carrying an Rh-positive foetus can develop antibodies that harm a later Rh-positive baby (erythroblastosis fetalis); an injection of anti-Rh antibodies after delivery prevents this.

Public-health milestones and issues

Issues: tuberculosis burden (India set a goal of ending TB by 2025, ahead of the SDG target of 2030); the double burden of malnutrition; rising NCDs; AMR; vector-borne diseases spreading with urbanisation and climate change; out-of-pocket health spending; uneven access in rural areas.

graph TD
    A[Pathogen enters body] --> B[Innate defences: skin, mucus, phagocytes]
    B --> C[Adaptive response]
    C --> D[B-cells make antibodies]
    C --> E[T-cells kill infected cells]
    D --> F[Memory cells]
    E --> F
    F --> G[Faster response next time - basis of vaccines]

Memory Anchors

Fat-soluble vitamins: “ADEK sits in the fat deck” → A, D, E, K; the rest (B, C) wash out in water.

Deficiency chain: “A-Night, B1-Beri, C-Scurvy, D-Rickets, K-Clot”.

Mosquito map: “Anopheles — mAlaria; Aedes — dengue, chikungunya, Zika (the ‘D-C-Z’ trio); Culex — Chronic filariasis and JE”.

Blood: “O gives, AB takes”.

For Prelims

For Mains

• Dimensions: nutrition security; health equity (rural–urban, gender); disease surveillance; AMR as a One Health issue (humans, animals, environment); climate and vector-borne disease; health financing.
• Keywords: double burden of malnutrition, hidden hunger, herd immunity, One Health, antimicrobial stewardship, universal health coverage, social determinants of health.
• Value-addition: NFHS-5 (2019–21) stunting 35.5% and anaemia in women 57.0%; polio eradication (2014); National Action Plan on AMR (2017); Mission Indradhanush (2014); POSHAN Abhiyaan (2018).

Common Traps

In the News

• October 2024 — WHO validates India’s elimination of trachoma as a public health problem. Track public-health updates on the current affairs page.

Practice

Prelims

Mains

Quick Revision

Key Takeaways

Related Topics

• Physics and Chemistry in Daily Life
• Everyday Science — quick revision
• Everyday Science — practice questions
• Biotechnology and Health — vaccines and gene therapy
• Social Justice and Welfare Schemes
• Agriculture and Food Security