Nutrition and dietetics

In short

Nutrition is the science of how the body obtains and uses food; dietetics is the applied practice of planning diets for health and for disease. For a nurse it is a daily clinical skill: screening nutritional status, counselling antenatal and paediatric clients, planning hospital diets, running nasogastric and total parenteral feeds, and delivering national programmes such as Anaemia Mukt Bharat, PM POSHAN and Poshan 2.0. It is examined as a full Basic Sciences paper in B.Sc Nursing (INC curriculum), reappears in Community Health Nursing, Medical-Surgical Nursing and Child Health, and is asked in every recruitment test — NORCET/AIIMS, ESIC, RRB, state PSC staff-nurse exams, DSSSB, military nursing — plus interviews at Apollo, Fortis, Manipal, Narayana Health and government hospitals. Indian reference values come from ICMR-NIN Nutrient Requirements and RDA for Indians (2020) and the NIN Dietary Guidelines for Indians (2024); food safety and fortification from FSSAI under the FSS Act, 2006.

Explained

Nutrients, energy and food groups

• Macronutrients supply energy: carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g. Micronutrients (vitamins, minerals) supply none but regulate metabolism.
• Desirable energy distribution: carbohydrate 55-60%, protein 10-15%, fat 20-30% of total calories; added sugar kept under ~5% of energy, salt under 5 g/day (WHO/NIN).
• Carbohydrates: monosaccharides (glucose, fructose), disaccharides (sucrose, lactose, maltose), polysaccharides (starch, glycogen, dietary fibre). Fibre — soluble (pectin, gums; lowers LDL, slows glucose absorption) and insoluble (cellulose; adds bulk, prevents constipation); ~25-30 g/day desirable.
• Proteins: chains of amino acids. Nine essential amino acids — histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine. Complete/first-class proteins (egg, milk, meat, fish) have all nine; cereal protein lacks lysine, pulse protein lacks methionine — eating them together gives mutual supplementation (the science behind dal-chawal, idli-sambar).
• Protein quality measures: biological value (egg = 100, reference), net protein utilisation (NPU), protein efficiency ratio (PER), digestibility-corrected amino acid score.
• Fats: saturated (ghee, coconut, palm), monounsaturated (groundnut, mustard, olive), polyunsaturated (safflower, sunflower, soya). Essential fatty acids — linoleic (n-6) and alpha-linolenic (n-3); EPA/DHA from fish. Trans fat limited by FSSAI to 2% of total oils/fats in edible oils and fats (phased in by 2022). Visible fat for a sedentary adult ≈ 25 g/day; blending oils is advised.
• ICMR five food groups: (1) cereals, millets and their products; (2) pulses and legumes; (3) milk, meat, egg, fish; (4) fruits and vegetables; (5) fats, oils, sugar. A balanced diet draws from all five in the right amounts; NIN's "My Plate for the Day" (2024) puts roughly half the plate as vegetables and fruit, with cereals under about 45% of energy and more millets, pulses, nuts and seeds.

Vitamins, minerals and deficiency disorders

• Fat-soluble: A, D, E, K — stored in liver/fat, toxic in excess. Water-soluble: B-complex and C — excreted, needed daily, lost in cooking water.
• Vitamin A: retinol (liver, egg, milk) and beta-carotene (green leafy vegetables, carrot, papaya, mango). Deficiency → night blindness → conjunctival xerosis → Bitot's spots → keratomalacia (irreversible blindness).
• Vitamin D: sunlight (7-dehydrocholesterol in skin) plus fortified milk/oil. Deficiency → rickets in children (bow legs, rickety rosary, craniotabes), osteomalacia in adults.
• Thiamine (B1): deficiency → beriberi (wet = cardiac failure and oedema; dry = peripheral neuritis), Wernicke-Korsakoff in alcoholics. Riboflavin (B2): angular stomatitis, cheilosis, glossitis. Niacin (B3): pellagra — the 3 Ds, dermatitis (casal's necklace), diarrhoea, dementia; common with maize-based diets.
• Folate and B12: megaloblastic anaemia; folate deficiency before conception/early pregnancy → neural tube defects. B12 deficiency (strict vegetarians, pernicious anaemia) adds subacute combined degeneration of the cord.
• Vitamin C: scurvy — bleeding gums, perifollicular haemorrhage, poor wound healing; also enhances non-haem iron absorption. Vitamin K: haemorrhagic disease of the newborn — 1 mg IM at birth.
• Iron: nutritional anaemia, India's largest deficiency problem (NFHS-5, 2019-21: about 57% of women 15-49 y and 67% of children 6-59 months anaemic). Iodine: goitre, cretinism, stillbirth — prevented by universal salt iodisation (iodised salt: not less than 30 ppm at manufacture, 15 ppm at consumer level). Calcium: tetany, poor bone mass. Zinc: growth retardation, diarrhoea, poor wound healing; zinc 20 mg (10 mg under 6 months) for 14 days is standard with ORS in childhood diarrhoea. Fluoride: deficiency → dental caries; excess (>1.5 mg/L water) → dental and skeletal fluorosis.
• Food toxins and hazards: aflatoxin (Aspergillus on groundnut/maize) → liver damage; lathyrism from khesari dal (BOAA); epidemic dropsy from argemone-adulterated mustard oil; antinutrients — phytates, oxalates, goitrogens, trypsin inhibitors — reduced by soaking, germination, fermentation and cooking.

Assessment of nutritional status (the nurse's ABCD)

• A — Anthropometry: weight, height, BMI, mid-upper arm circumference (MUAC), waist circumference, waist-hip ratio, triceps skinfold, head/chest circumference in infants (chest exceeds head by about 1 year).
• B — Biochemical: haemoglobin, serum albumin and prealbumin, serum ferritin, retinol, vitamin B12/folate, urinary iodine, nitrogen balance.
• C — Clinical: signs listed above; oedema, hair and skin changes, glossitis, pallor, dental state.
• D — Dietary: 24-hour recall, food frequency questionnaire, weighed food intake, diet history; E sometimes added for economic/ecological factors and vital statistics.
• BMI cut-offs for Asian Indians: underweight <18.0 (WHO uses <18.5), normal 18.0-22.9, overweight 23.0-24.9, obese ≥25.0; abdominal obesity at waist ≥90 cm (men), ≥80 cm (women) — Indian consensus guidelines.
• Growth monitoring: WHO child growth standards on the Mother and Child Protection Card; grading by weight-for-age (IAP) and by weight-for-height Z-score.
• Severe acute malnutrition (SAM) in 6-59 months: weight-for-height Z-score < −3 SD, or MUAC < 11.5 cm, or bilateral pitting pedal oedema. MAM: MUAC 11.5-12.5 cm or WHZ −2 to −3. SAM with complications or poor appetite → facility care at a Nutrition Rehabilitation Centre with F-75 in stabilisation and F-100/RUTF in rehabilitation, following WHO's 10 steps (treat/prevent hypoglycaemia, hypothermia, dehydration, electrolytes, infection, micronutrients — no iron in the first phase — cautious feeding, catch-up growth, stimulation, follow-up).

Protein energy malnutrition and nutrition through the life cycle

• Marasmus: severe energy deficit — gross wasting, "old man's face", no oedema, weight <60% expected. Kwashiorkor: oedema, hypoalbuminaemia, flaky-paint dermatosis, hair changes, fatty liver, apathy. Marasmic kwashiorkor: both.
• Infancy: exclusive breastfeeding for 6 months; colostrum (IgA, vitamin A) within the first hour; complementary feeding from completed 6 months with continued breastfeeding to 2 years. Breast milk ≈ 65-70 kcal/100 mL, lower protein and far better absorbed than cow's milk. India regulates infant food marketing through the IMS Act, 1992 (amended 2003).
• Pregnancy (ICMR-NIN 2020): about +350 kcal/day in the second and third trimesters; protein increment about +9.5 g/day (2nd trimester) and +22 g/day (3rd); iron 27 mg/day, folate 570 µg/day, calcium 1,000 mg/day. Expected total gain ~10-12 kg.
• Lactation: about +600 kcal/day (0-6 months) and +520 kcal/day (6-12 months), with protein increments of roughly +17 g and +13 g/day; extra fluids.
• Preschool and school age: energy-dense, frequent small feeds; PM POSHAN (mid-day meal) supplies 450 kcal + 12 g protein per child per day at primary level and 700 kcal + 20 g protein at upper primary.
• Adolescence: peak growth, highest iron and calcium needs; Weekly Iron and Folic Acid Supplementation (WIFS).
• Elderly: lower energy, same or higher protein, more calcium, vitamin D, B12, fibre and fluid; soft textures for poor dentition.

Diet therapy — hospital and disease diets

• Purposes of diet therapy: maintain or improve nutritional status, correct deficiencies, rest an organ, adjust to the body's ability to digest/metabolise/excrete.
• Consistency diets: clear fluid (water, clear soup, barley water — ~400-500 kcal, nutritionally inadequate, short-term only) → full fluid (milk, custard) → soft (cooked, low fibre) → regular. Bland, low-residue and high-fibre diets for GI conditions.
• Diabetes mellitus: calories set for ideal body weight and activity; carbohydrate 50-60% from low-glycaemic-index complex sources; fibre 25-40 g; consistent carbohydrate at each meal with insulin timing; sugar restricted, non-nutritive sweeteners optional; alcohol discouraged. Use food exchange lists for planning.
• Hypertension and heart disease: sodium restricted (no added salt ~2 g Na; moderate 1 g; severe 0.5 g), saturated and trans fat reduced, cholesterol limited, potassium and fibre increased — DASH-type pattern.
• Chronic kidney disease: controlled protein (individualised, often around 0.6-0.8 g/kg in pre-dialysis, raised on dialysis), restricted sodium, potassium and phosphorus, adequate calories, fluid as per urine output plus insensible loss. Nephrotic syndrome: normal-to-high protein, low salt.
• Liver disease: high calorie, high carbohydrate, moderate protein; protein restricted only in overt encephalopathy; salt and fluid restricted in ascites; no alcohol.
• Burns, trauma, sepsis, cancer, HIV: high calorie, high protein, high micronutrient diets (hypermetabolic states).
• Peptic ulcer: small frequent bland meals, avoid irritants; coeliac disease: lifelong gluten-free (no wheat, barley, rye; rice, maize, millets allowed); lactose intolerance: curd/yoghurt tolerated better than milk; gout: low purine, high fluid; ketogenic diet: refractory epilepsy.
• Enteral nutrition (gut usable, oral intake inadequate): nasogastric, nasojejunal, gastrostomy/PEG, jejunostomy. Nursing care — check placement and residual volume, head of bed 30-45°, room-temperature feed, flush 30-50 mL water before and after, hang time limited, feed held if residual is high. Complications: aspiration, diarrhoea, blocked tube, hyperglycaemia.
• Parenteral nutrition: peripheral (PPN) for short-term, low-osmolarity feeds; TPN through a central line when the gut cannot be used. Strict asepsis, dedicated lumen, no bolus medication in the TPN line, blood glucose and electrolyte monitoring, never stop abruptly. Complications: catheter sepsis, hyperglycaemia, electrolyte shifts, cholestasis.
• Refeeding syndrome: on refeeding a severely malnourished patient, insulin drives phosphate, potassium and magnesium into cells → arrhythmia, heart failure, death. Prevent by starting feeds low and slow, giving thiamine first and monitoring electrolytes.

Food hygiene, standards and national programmes

• FSS Act, 2006 with the FSSAI regulations is India's single food law (replacing the PFA Act, 1954); it covers licensing, standards, labelling, additives, contaminants and recall. Packaged foods carry FSSAI licence numbers; the +F logo marks fortified food.
• Food Safety and Standards (Fortification of Foods) Regulations, 2018: salt with iodine and iron (double-fortified salt), edible oil and milk with vitamins A and D, wheat flour and rice with iron, folic acid and B12. Fortified rice is distributed through PDS, ICDS and PM POSHAN.
• Food-borne illness and hygiene: typhoid, cholera, hepatitis A/E, amoebiasis, salmonellosis, staphylococcal and *Bacillus cereus* toxin, botulism. Control by safe water, hand-washing, cooking to safe temperature, holding food out of the 5-60 °C danger zone, separating raw and cooked food, pest control and fit food handlers (HACCP principles).
• Preservation: drying/dehydration, refrigeration and freezing, canning, pasteurisation (HTST 72 °C/15 s), UHT, salting, sugaring, pickling, fermentation, irradiation, permitted chemical preservatives.
• Cooking and nutrient conservation: avoid prolonged boiling and discarding water, cook covered, do not add cooking soda, minimise reheating; germination raises vitamin C and lowers phytate; fermentation improves B vitamins and protein availability; parboiling retains thiamine in rice.
• Programmes a nurse delivers: ICDS (1975) with supplementary nutrition (≈500 kcal + 12-15 g protein for 6 months-6 years; ≈800 kcal + 20-25 g for severely underweight; ≈600 kcal + 18-20 g for pregnant and lactating women); Saksham Anganwadi and Poshan 2.0 (which absorbed POSHAN Abhiyaan, 2018); PM POSHAN; Anaemia Mukt Bharat (6×6×6 strategy); National Iodine Deficiency Disorders Control Programme; Vitamin A prophylaxis — 1 lakh IU at 9 months with measles-rubella, then 2 lakh IU six-monthly up to 5 years (9 doses); biannual albendazole 400 mg; PMMVY and Janani Suraksha Yojana for maternal support.
• IFA supplementation (Anaemia Mukt Bharat): 6-59 months — IFA syrup 1 mL (20 mg iron + 100 µg folic acid) twice weekly; 5-9 years — pink tablet (45 mg iron + 400 µg folic acid) weekly; 10-19 years — blue tablet (60 mg iron + 500 µg folic acid) weekly; pregnant and lactating women — one IFA tablet (60 mg elemental iron + 500 µg folic acid) daily for 180 days antenatal and 180 days postpartum, after the first trimester. Doses are revised from time to time — follow the current national operational guideline.

Key points

• Balanced diet - food from all five ICMR groups in amounts that meet energy, nutrients and a small reserve.
• Energy values - carbohydrate 4, protein 4, fat 9 kcal/g; fat is the most energy-dense.
• ICMR-NIN 2020 reference adult - sedentary man ≈ 2,110 kcal/day, sedentary woman ≈ 1,660 kcal/day; reference weights 65 kg and 55 kg.
• Protein RDA - 0.83 g/kg/day for adults (≈54 g man, ≈46 g woman); requirement rises in pregnancy, lactation, burns, sepsis and recovery.
• Mutual supplementation - cereal (low lysine) plus pulse (low methionine) gives near-complete protein; classic ratio 4:1 to 5:1.
• Essential nutrients - 9 essential amino acids, 2 essential fatty acids (linoleic, alpha-linolenic).
• Asian-Indian BMI - obesity from ≥25 kg/m², overweight 23-24.9; waist ≥90 cm men / ≥80 cm women is abdominal obesity.
• SAM criteria - MUAC <11.5 cm, or WHZ < −3 SD, or bilateral pitting oedema in 6-59 months.
• Marasmus vs kwashiorkor - wasting without oedema vs oedema with hypoalbuminaemia.
• F-75 then F-100/RUTF - stabilisation before catch-up growth; no iron in the stabilisation phase.
• Refeeding syndrome - falling phosphate, potassium and magnesium on refeeding; start low, give thiamine.
• Vitamin A prophylaxis - 1 lakh IU at 9 months, then 2 lakh IU six-monthly to 5 years.
• Iodised salt - not less than 30 ppm iodine at manufacture, 15 ppm at consumer level.
• Vitamin C with iron - enhances non-haem iron absorption; tea, coffee, phytates and calcium inhibit it.
• Clear fluid diet - nutritionally inadequate; a bridging diet for 24-48 hours only.
• Enteral before parenteral - "if the gut works, use it"; TPN only when the gut cannot be used.
• Nitrogen - protein contains about 16% nitrogen, so protein = nitrogen × 6.25.
• Law - FSS Act, 2006 is the governing food law; fortification follows the FSSAI Regulations, 2018.

Formulas and examples

Example 1 — BMI and obesity grading. A 38-year-old woman weighs 72 kg and is 1.60 m tall.

• Height² = 1.60 × 1.60 = 2.56 m².
• BMI = 72 ÷ 2.56 = 28.1 kg/m².
• By Asian-Indian cut-offs this is obese (≥25); by WHO international cut-offs it would be only "overweight" (25-29.9). Her waist is 94 cm and hips 100 cm → WHR = 94/100 = 0.94, above 0.85 — abdominal obesity, so cardiometabolic risk is high.

Example 2 — Energy and macronutrient distribution of a day's diet. Intake: carbohydrate 300 g, protein 60 g, fat 50 g.

• Carbohydrate = 300 × 4 = 1,200 kcal; protein = 60 × 4 = 240 kcal; fat = 50 × 9 = 450 kcal.
• Total = 1,200 + 240 + 450 = 1,890 kcal.
• Shares: carbohydrate 1,200/1,890 = 63.5%, protein 240/1,890 = 12.7%, fat 450/1,890 = 23.8%.
• Protein (12.7%) and fat (23.8%) lie inside the recommended ranges (10-15% and 20-30%), but carbohydrate at 63.5% is above the recommended 55-60% — swap some rice for pulses and vegetables.

Example 3 — Energy and protein prescription for a post-operative patient. Man, 70 kg, 170 cm, 40 years, bed-rest after bowel surgery, stress factor 1.3.

• BMR = (10 × 70) + (6.25 × 170) − (5 × 40) + 5 = 700 + 1,062.5 − 200 + 5 = 1,567.5 kcal/day.
• Activity (bed-rest, 1.2) → 1,567.5 × 1.2 = 1,881 kcal; stress 1.3 → 1,881 × 1.3 ≈ 2,445 kcal/day.
• Protein at 1.5 g/kg (catabolic state) = 70 × 1.5 = 105 g/day; at the healthy RDA of 0.83 g/kg it would be only 58 g — the surgical state nearly doubles it.
• If 105 g protein is given, protein supplies 420 kcal — about 17% of 2,445 kcal.

Example 4 — Nitrogen balance. Same patient receives 105 g protein; 24-hour urinary urea nitrogen is 14 g.

• Nitrogen intake = 105 ÷ 6.25 = 16.8 g.
• Nitrogen output = 14 + 4 = 18 g.
• Balance = 16.8 − 18 = −1.2 g/day — still catabolic; raise protein and calories (calories spare protein).

Example 5 — Paediatric fluid and burns energy.

• A 23 kg child: fluid = (10 × 100) + (10 × 50) + (3 × 20) = 1,000 + 500 + 60 = 1,560 mL/day ≈ 65 mL/hour.
• A 60 kg adult with 30% TBSA burns (Curreri): (25 × 60) + (40 × 30) = 1,500 + 1,200 = 2,700 kcal/day, with protein about 1.5-2 g/kg = 90-120 g/day.

Example 6 — Iron supplementation. An anaemic adult is prescribed ferrous sulphate 200 mg three times daily.

• Elemental iron ≈ 20% of ferrous sulphate → 200 × 0.20 = 40 mg per tablet; three tablets = 120 mg elemental iron/day, within the usual 100-200 mg therapeutic range.
• Counselling: take on an empty stomach with lemon water or another vitamin-C source, not with tea, milk or antacids; warn about black stools and constipation.

Where it is used

• Hospital dietetics: diet sheets and therapeutic diet planning in dietary departments of AIIMS, PGIMER, CMC Vellore, Apollo, Fortis and Manipal; nurse-dietitian handover of NPO, diabetic and renal diets.
• Critical care and surgical wards: NG/PEG feeding, TPN monitoring, refeeding precautions, perioperative nutrition screening, pressure-ulcer and wound-healing nutrition.
• Community health and government service: ANM/LHV and staff-nurse work in ICDS anganwadis, Nutrition Rehabilitation Centres, VHSNDs, school health under PM POSHAN, Anaemia Mukt Bharat IFA distribution, growth monitoring on the MCP card.
• Maternal and child health: antenatal diet counselling, breastfeeding and lactation support, complementary feeding demonstration, management of SAM/MAM; roles as lactation consultant or nutrition counsellor.
• Industry and corporate roles: nutrition advisers with infant-food and nutraceutical companies, diabetes educators, FSSAI-trained food safety supervisors in hospital kitchens, catering and hostel mess nutrition.
• Education and research: community nutrition surveys (NFHS, CNNS), nursing faculty posts, programme evaluation with NIN Hyderabad and state nutrition cells.

Interview questions

• Q: What is a balanced diet? A: A diet containing foods from all five ICMR food groups in proportions that meet energy and all nutrient needs with a small margin for lean periods of illness or extra demand.
• Q: How many kilocalories do carbohydrate, protein and fat give per gram? A: 4, 4 and 9 kcal per gram respectively; alcohol gives about 7.
• Q: Why are dal and rice eaten together? A: Cereal protein is low in lysine and pulse protein low in methionine; eaten together they supplement each other and give a near-complete amino acid profile.
• Q: What are the criteria for severe acute malnutrition in a child of 6-59 months? A: Weight-for-height Z-score below −3 SD, or MUAC under 11.5 cm, or bilateral pitting pedal oedema — any one is enough.
• Q: Why is iron withheld in the stabilisation phase of SAM? A: Free iron promotes bacterial growth and oxidative damage in a metabolically unstable child; it is added only in the rehabilitation phase, once appetite and weight gain return.
• Q: What is refeeding syndrome and how do you prevent it? A: A fall in serum phosphate, potassium and magnesium when a severely malnourished patient is fed too fast, causing arrhythmias and cardiac failure; prevent by starting at low calories, giving thiamine before feeds and monitoring electrolytes daily.
• Q: How do you confirm nasogastric tube placement before a feed? A: By checking the external tube marking, aspirating gastric content and testing pH (acidic), and by X-ray confirmation when first placed; the air-auscultation method alone is not reliable.
• Q: Which vitamin deficiency causes Bitot's spots, and what is the national prophylaxis schedule? A: Vitamin A; 1 lakh IU at 9 months with measles-rubella vaccine, then 2 lakh IU every six months up to 5 years.
• Q: What is the difference between enteral and parenteral nutrition, and when would you choose each? A: Enteral feeds go into a functioning gut through a tube; parenteral bypasses the gut into a vein. Enteral is preferred as it maintains gut integrity and costs less; parenteral is used when the gut is obstructed, perforated, ischaemic or fails to absorb.
• Q: What are the BMI cut-offs for Indians and why do they differ from WHO's? A: Overweight from 23 and obesity from 25 kg/m², because Indians show higher body fat, visceral fat and diabetes risk at a lower BMI than Europeans.
• Q: How does vitamin C help an anaemic patient? A: It reduces ferric to ferrous iron and keeps it soluble, improving absorption of non-haem iron; so IFA is taken with citrus or amla, not with tea or milk.
• Q: Which law governs food safety in India and what does the +F logo mean? A: The Food Safety and Standards Act, 2006, administered by FSSAI; the +F logo identifies food fortified under the FSSAI Fortification of Foods Regulations, 2018.

Common mistakes

• Using WHO BMI cut-offs instead of the Asian-Indian ones, so obese Indian patients are classified only as overweight.
• Multiplying protein by 9 or fat by 4 in energy calculations, and forgetting to convert kJ to kcal (1 kcal = 4.184 kJ).
• Quoting pregnancy needs as "+350 kcal throughout" — the increment applies to the second and third trimesters, not the first.
• Writing "high protein" for every sick patient, including hepatic encephalopathy and advanced pre-dialysis CKD where protein is restricted.
• Continuing a clear fluid diet for days; it cannot meet protein or micronutrient needs.
• In SAM, jumping straight to catch-up feeding or giving iron early, and missing hypoglycaemia and hypothermia management.
• Confusing MUAC cut-offs (11.5 cm for SAM, 11.5-12.5 cm for MAM) and mixing up the IFA tablet colours and schedules of Anaemia Mukt Bharat.

Related topics

Anatomy and physiology essentials · Microbiology for nurses · Pharmacology for nurses · Community health nursing and national health programmes · Child health nursing and growth monitoring · Medical-surgical nursing: metabolic and endocrine disorders