Nutrition & Environmental Health
1. What this chapter covers, and how NEET PG actually tests it
Questions here ask for a deficiency's clinical signs, a malnutrition classification cut-off, a water treatment standard or a programme detail.
The organising principle is that both halves are about exposure: nutrition is what reaches the body in too small a quantity, and environmental health is what reaches it in too large a quantity.
The intervention in both cases is to change what reaches the person, which is why salt iodisation and water chlorination are structurally the same kind of measure: a change made once, at a central point, that protects an entire population without requiring anyone to do anything.
That property is what makes such measures the most cost-effective in public health, and it is also why they are politically durable in a way that behaviour-change programmes are not.
2. Nutritional requirements
A balanced diet supplies roughly 50 to 70 per cent of energy from carbohydrate, 20 to 30 per cent from fat and 10 to 15 per cent from protein.
Adult protein requirement is approximately one gram per kilogram body weight daily, rising in pregnancy, lactation and childhood.
Requirements are expressed against a reference man of 60 kilograms and a reference woman of 55 kilograms, both aged between eighteen and twenty-nine and doing sedentary work.
Recommended intakes are set above the average requirement deliberately, at a level covering nearly the whole population, which is why an individual eating below the recommendation is not necessarily deficient.
3. Protein energy malnutrition
3.1 The two classical forms
| Feature | Kwashiorkor | Marasmus |
|---|---|---|
| Oedema | Present, bilateral pitting | Absent |
| Wasting | Masked by oedema | Severe and obvious |
| Face | Moon face | Old man's face |
| Hair and skin | Depigmented hair, flaky paint dermatosis | Relatively spared |
| Liver | Enlarged and fatty | Not enlarged |
| Behaviour | Apathetic, miserable | Alert and irritable |
The oedema of kwashiorkor is what defines it, and its presence alone classifies a child as severely malnourished regardless of weight.
3.2 Classification
Three indices describe different problems, and confusing them is the commonest error in the chapter.
| Index | Measures | Reflects |
|---|---|---|
| Weight for height | Wasting | Acute malnutrition |
| Height for age | Stunting | Chronic malnutrition |
| Weight for age | Underweight | Both together |
Stunting is the more serious finding at population level, because it reflects sustained deprivation and is associated with irreversible loss of cognitive potential, whereas wasting reflects a recent insult and can be reversed.
Severe acute malnutrition is defined by weight for height below three standard deviations, or a mid-upper arm circumference below 11.5 centimetres in children aged six to fifty-nine months, or bilateral pitting oedema.
Moderate acute malnutrition occupies the band between two and three standard deviations, with a mid-upper arm circumference of 11.5 to 12.5 centimetres.
Mid-upper arm circumference is used in community screening because it needs only a coloured tape, requires no scales or height board, and changes little with age between one and five years.
3.3 Management
A child with severe acute malnutrition and any medical complication, or no appetite, requires inpatient care at a nutrition rehabilitation centre.
An uncomplicated case with preserved appetite is managed at home with ready-to-use therapeutic food, which is energy dense, requires no water and therefore carries no contamination risk.
Inpatient management follows a ten-step sequence with two phases: stabilisation using a lower-energy formula, then rehabilitation using a higher-energy one to drive catch-up growth.
Feeding is cautious at first for a specific reason. Refeeding a severely malnourished child too quickly precipitates the refeeding syndrome, in which the shift from fat to carbohydrate metabolism drives potassium, magnesium and especially phosphate into cells and can cause fatal cardiac failure.
Hypoglycaemia, hypothermia, dehydration and infection are treated before nutrition is pushed, and antibiotics are given routinely because the usual signs of infection are absent in these children.
4. Micronutrients
4.1 Vitamin A
Deficiency is graded by the World Health Organization, and the sequence follows the anatomy.
| Grade | Finding |
|---|---|
| XN | Night blindness |
| X1A | Conjunctival xerosis |
| X1B | Bitot spot |
| X2 | Corneal xerosis |
| X3A | Corneal ulceration under one third |
| X3B | Ulceration of one third or more, or keratomalacia |
| XS | Corneal scar |
Night blindness comes first because rod photoreceptors depend on retinal, and the conjunctiva is affected before the cornea because it is the less critical epithelium.
Prophylaxis is 100,000 international units at nine months with the first measles dose, then 200,000 six-monthly to five years, giving nine doses.
4.2 Iodine
Requirement is about 150 micrograms daily for adults and 250 in pregnancy.
Salt is iodised at 30 parts per million at production and must contain at least 15 parts per million at the consumer end, the difference allowing for loss in transport and storage.
Deficiency in pregnancy is the consequence that matters most, because maternal iodine is required for fetal brain development and the resulting cretinism is irreversible.
Population status is assessed by goitre prevalence in school children aged six to twelve and by median urinary iodine excretion, since urinary excretion reflects recent intake directly.
4.3 The others
Iron deficiency is the commonest micronutrient deficiency in India and is addressed by supplementation, fortification and deworming together.
Zinc deficiency causes growth failure, impaired immunity and delayed wound healing, and zinc is given therapeutically in childhood diarrhoea.
Vitamin D deficiency is widespread despite abundant sunlight, because of skin pigmentation, covering clothing and indoor living.
Fortification of staples with iron, iodine, vitamin A and vitamin D is now permitted and increasingly used, and it works on the same principle as salt iodisation: protection delivered without requiring a behaviour change.
4.4 Programmes
Integrated child development services provide supplementary nutrition through anganwadi centres, and the national nutrition mission coordinates the effort across ministries.
The midday meal scheme provides a cooked meal in government schools, and its effect on enrolment and attendance has been larger than its nutritional effect alone.
4.5 Assessing nutritional status
Assessment uses four approaches remembered as anthropometry, biochemical tests, clinical examination and dietary assessment.
Anthropometry is the mainstay in the field because it needs no laboratory, and the standard measurements are weight, height or length, mid-upper arm circumference and head circumference.
Body mass index cut-offs for Indian and other Asian populations are set lower than the international ones, with overweight from 23 and obesity from 25, because cardiometabolic risk appears at a lower body mass in these populations.
That lower threshold is not an arbitrary adjustment but reflects a genuinely different body composition, with more visceral fat and less muscle at the same body mass index, the pattern sometimes described as the thin-fat phenotype.
Waist circumference and waist-hip ratio add information that body mass index misses, because they capture the distribution of fat rather than its quantity.
5. Food safety and food toxicants
Food-borne illness divides into infection, in which organisms multiply in the host, and intoxication, in which a preformed toxin acts directly.
The incubation period distinguishes them at once. An illness beginning within a few hours of eating is almost always an intoxication, while one beginning after twelve hours or more suggests infection.
Staphylococcal food poisoning begins within one to six hours with violent vomiting and no fever, because the enterotoxin is preformed and heat stable, so reheating the food does not help.
Clostridium perfringens and salmonella take longer, since the organisms must multiply in the gut before symptoms appear.
Botulism is the exception that must never be missed, presenting with descending paralysis and cranial nerve palsies rather than gastroenteritis.
Several classic Indian food toxicants are examined repeatedly.
| Toxicant | Source | Disease |
|---|---|---|
| Argemone oil | Adulterated mustard oil | Epidemic dropsy |
| Beta-oxalyl amino alanine | Lathyrus sativus, the kesari dal | Lathyrism, spastic paraplegia |
| Aflatoxin | Aspergillus on stored groundnut and maize | Hepatotoxicity, hepatocellular carcinoma |
| Excess fluoride | Groundwater | Dental and skeletal fluorosis |
Epidemic dropsy presents with pitting oedema of the legs, gastrointestinal upset and characteristically dilated cutaneous capillaries, and it is diagnosed by testing the oil rather than the patient.
Lathyrism affects young adults eating the pulse as a staple during drought, when little else grows, and the paralysis is irreversible once established.
6. Water
5.1 Quantity and treatment
Urban supply is planned at roughly 150 to 200 litres per person daily, while the minimum for survival with basic hygiene is far lower.
Large-scale purification has three stages: storage, filtration and chlorination.
Storage for about two weeks removes most suspended matter and reduces bacterial counts substantially through sedimentation and natural die-off.
| Filter | Rate | Bacterial removal |
|---|---|---|
| Slow sand | 0.2 to 0.3 cubic metres per square metre per hour | 99.9 to 99.99 per cent |
| Rapid sand | 5 to 15 cubic metres per square metre per hour | Lower, requires reliable chlorination |
The slow sand filter works through its biological layer, the schmutzdecke, a slimy film of algae and bacteria on the surface that does the actual purification, which is why a newly cleaned filter must be allowed to ripen before use.
The rapid sand filter is faster and needs less land but removes fewer organisms, so chlorination becomes essential rather than merely confirmatory.
5.2 Chlorination
Chlorine acts as hypochlorous acid, which is why it is far less effective above pH 8, and why pH must be controlled for disinfection to work.
Break-point chlorination means adding enough chlorine to satisfy all the demand from organic matter and ammonia, beyond which further chlorine remains free and available.
A free residual chlorine of 0.5 milligrams per litre after one hour of contact is the standard, and it is set with a margin so that recontamination in the distribution system is still countered.
Chlorine does not kill protozoal cysts reliably, which is why Cryptosporidium and Giardia outbreaks occur in properly chlorinated supplies and why filtration cannot be dispensed with.
Horrock's apparatus determines the dose of bleaching powder needed for a given water source in field conditions.
5.3 Water-related disease
| Category | Examples |
|---|---|
| Waterborne | Cholera, typhoid, hepatitis A and E, polio |
| Water-washed, from scarcity | Trachoma, scabies, skin and eye infection |
| Water-based | Schistosomiasis, guinea worm |
| Water-related vector | Malaria, dengue, filariasis |
The distinction matters for policy: waterborne disease requires clean water, but water-washed disease requires abundant water, and a scheme delivering a small quantity of very pure water addresses only the first.
7. Air, waste and housing
Indoor air pollution from biomass cooking fuel is a major cause of respiratory disease in Indian women and children, and the programme response has been to subsidise clean cooking fuel.
Outdoor air quality is monitored as an index dominated in Indian cities by fine particulate matter, which penetrates to the alveoli and enters the circulation.
Refuse disposal by sanitary landfill is regarded as the most satisfactory method where land is available, with composting used widely and incineration reserved for hazardous material.
Composting can be aerobic or anaerobic, the two classical Indian methods being distinguished on exactly that basis, with the aerobic method faster and producing less odour.
Excreta disposal in rural areas uses the twin-pit pour-flush latrine, which allows one pit to be used while the other's contents decompose into safe manure.
Housing standards specify a minimum floor space per person, a window area of about one fifth of floor area, and adequate air changes, with overcrowding defined by persons per room and by floor area.
7.1 Occupational exposure
Occupational disease follows the same exposure logic, and the pneumoconioses are the classic examples.
| Disease | Exposure | Note |
|---|---|---|
| Silicosis | Free silica in mining, stone crushing, sandblasting | Predisposes strongly to tuberculosis |
| Asbestosis | Asbestos in construction and shipbreaking | Causes mesothelioma decades later |
| Coal worker's pneumoconiosis | Coal dust | Progressive massive fibrosis in advanced disease |
| Byssinosis | Cotton dust | Chest tightness worst on the first working day |
Silicosis matters disproportionately in India because it markedly increases susceptibility to tuberculosis, so a dusty occupation and a chronic cough together should raise both diagnoses rather than one.
Byssinosis is distinctive because symptoms are worst on returning to work after a break, which is why it was historically called Monday fever.
Control follows a fixed hierarchy: substitution of the hazardous material, then engineering control such as enclosure and ventilation, then administrative measures limiting exposure time, and only last personal protective equipment.
Protective equipment is placed last deliberately, because it depends on the worker wearing it correctly every time and fails the moment they do not.
Employees' state insurance provides medical care and cash benefits to covered workers, and factory legislation sets the statutory requirements for working conditions and periodic examination.
8. Worked examples
Example 1. A two-year-old has a mid-upper arm circumference of 11.0 centimetres but a normal weight for height. What is the classification?
Severe acute malnutrition. Any one of the three criteria is sufficient: weight for height below three standard deviations, mid-upper arm circumference below 11.5 centimetres, or bilateral pitting oedema.
Example 2. A supply is chlorinated correctly but a Cryptosporidium outbreak occurs. How?
Chlorine does not reliably inactivate protozoal cysts at the concentrations used in water treatment. Filtration is what removes them, so adequate free residual chlorine does not guarantee safety against these organisms.
Example 3. A child with severe acute malnutrition develops cardiac failure two days after admission. What is the likely mechanism?
Refeeding syndrome. The shift to carbohydrate metabolism drives phosphate, potassium and magnesium into cells, and the resulting depletion causes cardiac failure. This is why feeding begins cautiously with a lower-energy formula.
Summary
Both halves concern exposure: too little reaching the body, or too much.
Central measures such as salt iodisation and water chlorination protect populations without requiring individual behaviour change, which is why they are the most cost-effective interventions available.
A balanced diet gives 50 to 70 per cent of energy from carbohydrate, 20 to 30 from fat and 10 to 15 from protein.
Kwashiorkor is defined by bilateral pitting oedema, a moon face, hair and skin changes and a fatty liver; marasmus by severe visible wasting with an alert child.
Weight for height measures wasting, height for age measures stunting, and weight for age measures underweight.
Stunting reflects chronic deprivation and irreversible cognitive loss; wasting reflects a recent and reversible insult.
Severe acute malnutrition is weight for height below three standard deviations, mid-upper arm circumference under 11.5 centimetres, or bilateral oedema, any one being sufficient.
Mid-upper arm circumference is used for screening because it needs only a tape and varies little between one and five years.
Uncomplicated cases with appetite are treated at home with ready-to-use therapeutic food.
Feeding starts cautiously because refeeding syndrome drives phosphate, potassium and magnesium into cells and can be fatal.
Vitamin A deficiency runs from night blindness through Bitot spot to corneal ulceration and keratomalacia.
Vitamin A prophylaxis is 100,000 units at nine months then 200,000 six-monthly to five years, nine doses.
Salt is iodised at 30 parts per million at production and must reach the consumer at 15.
Iodine deficiency in pregnancy causes irreversible cretinism, which is the consequence that drives the programme.
Iodine status is assessed by goitre prevalence in six to twelve year olds and median urinary iodine excretion.
Water purification is storage, filtration and chlorination.
The slow sand filter works through its biological schmutzdecke and must ripen before use.
The rapid sand filter is faster but removes fewer organisms, making chlorination essential.
Chlorine acts as hypochlorous acid and fails above pH 8.
The standard is 0.5 milligrams per litre of free residual chlorine after one hour of contact.
Chlorine does not reliably kill protozoal cysts, so filtration remains necessary.
Waterborne disease needs clean water while water-washed disease needs abundant water, and the two require different schemes.
Indoor biomass smoke is a major cause of respiratory disease in Indian women and children.
Sanitary landfill is the most satisfactory refuse disposal method where land is available.
Asian body mass index cut-offs are lower, with overweight from 23 and obesity from 25, reflecting the thin-fat phenotype.
Food intoxication begins within hours because the toxin is preformed; food infection takes twelve hours or more.
Staphylococcal toxin is heat stable, so reheating does not make the food safe.
Argemone oil in mustard oil causes epidemic dropsy, and Lathyrus sativus causes irreversible spastic paraplegia.
Silicosis strongly predisposes to tuberculosis, and byssinosis is worst on the first working day after a break.
Hazard control runs substitution, then engineering, then administrative measures, with protective equipment last because it depends on the worker.
