Nutrition basics

In short

Nutrition is the science of how the body takes in food, digests and absorbs the nutrients in it, uses them for energy, growth, repair and regulation, and excretes what is left. "Nutrition basics" covers the six nutrient classes, how food energy is measured, how much of each nutrient a person needs (the ICMR–NIN Recommended Dietary Allowances), how diet quality is judged, and what happens when intake is too little or too much. In India it underpins the Food Safety and Standards (Labelling and Display) Regulations, 2020, the Fortification of Foods Regulations, 2018, PM POSHAN, POSHAN Abhiyaan and Anaemia Mukt Bharat. It is examined in B.Sc. Food Science, Nutrition and Dietetics papers, in the FSSAI Food Safety Officer and Technical Officer exams, UGC-NET Home Science and CSIR-UGC Food Science, and asked in interviews for QA, product development (nutrition labelling, claims) and dietetics roles at Nestlé, ITC, Britannia, Hindustan Unilever, Amul, Mother Dairy and hospital dietary departments.

Explained

Nutrients and their functions

• Nutrient: a chemical substance in food that the body needs for energy, structure or regulation. Six classes: carbohydrates, proteins, fats, vitamins, minerals and water (dietary fibre and phytonutrients are counted separately as non-nutrient dietary components).
• Macronutrients (grams per day): carbohydrate, protein, fat, water. Micronutrients (milligrams or micrograms per day): vitamins and minerals.
• Functions, the standard three-way grouping: energy-yielding (carbohydrate, fat, protein), body-building/repair (protein, minerals, water), protective and regulatory (vitamins, minerals, fibre, water).
• Essential nutrient: the body cannot synthesise it at all, or fast enough — so it must come from food. Includes 9 indispensable amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine), the essential fatty acids (linoleic acid – n-6; α-linolenic acid – n-3), all vitamins, and the essential minerals.
• Conditionally essential: normally synthesised but required from diet in stress, prematurity or disease — e.g. glutamine, arginine, taurine, cysteine.
• Acceptable macronutrient distribution (ICMR–NIN Dietary Guidelines for Indians, 2024): carbohydrate about 50–55% of energy (cereals not more than ~45%), fat 20–30% (visible fat 20–25 g/day for a sedentary adult), protein 10–15%, added sugar below 5% of total energy, salt under 5 g/day.
• Water: about 2–3 litres/day from fluids and food; the only nutrient whose lack kills within days.
• Dietary fibre: soluble (pectin, gums, β-glucan — lowers LDL cholesterol, slows glucose absorption) and insoluble (cellulose, hemicellulose, lignin — faecal bulk, transit time). Recommended intake about 25–30 g/day (editions differ; ICMR expresses it per 1,000 kcal).

Food energy: units, Atwater factors and requirement

• Unit: 1 kilocalorie (kcal) = 4.184 kJ. Labels in India may declare energy in kcal (kJ optional).
• Gross energy is measured in a bomb calorimeter; physiological (metabolisable) energy subtracts faecal and urinary losses. Hence the Atwater factors: carbohydrate 4, protein 4, fat 9, alcohol 7, dietary fibre ~2, polyols ~2.4 kcal/g.
• Why protein gives 4 and not 5.65: its gross energy is ~5.65 kcal/g, but urea and other nitrogenous waste carry away about 1.25 kcal/g; digestibility accounts for the rest.
• Total energy expenditure (TEE) has three parts: BMR (60–75%), thermic effect of food / SDA (~10%, highest for protein at 20–30%), and physical activity (15–30%, the variable part); growth, pregnancy and lactation add to it.
• BMR: energy spent at complete rest, awake, 12–14 h after a meal, in a thermoneutral environment. Measured by indirect calorimetry (O₂ consumed, CO₂ produced; respiratory quotient RQ = VCO₂/VO₂ — 1.0 for carbohydrate, 0.7 for fat, ~0.8 for protein, ~0.85 mixed diet). RMR is measured under less strict conditions and is ~10% higher.
• BMR raised by: larger lean body mass, male sex, growth, fever (about +13% per °C), hyperthyroidism, cold, pregnancy, caffeine/nicotine. Lowered by: ageing, starvation, hypothyroidism, loss of muscle.
• Factorial method (ICMR–NIN 2020): TEE = BMR × PAL (physical activity level), with PAL ≈ 1.53 sedentary, ≈ 1.8 moderate, ≈ 2.2–2.3 heavy.
• ICMR–NIN 2020 energy requirements for the reference adult (man 65 kg, woman 55 kg, 19–39 y, healthy, BMI ~22): sedentary man ≈ 2,110 kcal/day, moderate ≈ 2,710, heavy ≈ 3,470; sedentary woman ≈ 1,660, moderate ≈ 2,130, heavy ≈ 2,720. Pregnancy adds ~350 kcal (2nd and 3rd trimester); lactation 0–6 months ~600 kcal.

EAR, RDA, AI, TUL — reading the requirement tables

• EAR (Estimated Average Requirement): intake that meets the need of 50% of a healthy group. Used to assess *groups* and in dietary planning for populations.
• RDA: EAR + 2 SD, meeting the need of 97.5% of the group. Used as a *goal for an individual*; an intake below RDA is not by itself a deficiency.
• AI (Adequate Intake): used when data are too few to set an EAR (e.g. infants 0–6 months, taken from breast-milk intake).
• TUL (Tolerable Upper Limit): highest chronic daily intake unlikely to cause harm — important for vitamin A, vitamin D, iron, iodine, selenium and fortified foods/supplements.
• Energy is the exception: it is given as an average requirement (EAR), never RDA + 2 SD, because recommending an excess would cause obesity.
• ICMR–NIN 2020 shift: moved from "balanced diet" tables to EAR + RDA + TUL, raised reference body weights (man 60 → 65 kg, woman 55 kg), and set protein from EAR 0.83 g/kg/day of good-quality protein → RDA ≈ 54 g/day (man) and 46 g/day (woman).
• Indicative adult RDAs (ICMR–NIN 2020): calcium 1,000 mg; iron 19 mg (man) / 29 mg (woman); zinc 17 / 13.2 mg; iodine 150 µg; vitamin A 1,000 / 840 µg retinol equivalent; vitamin C 80 mg; vitamin D 600 IU (15 µg); folate 300 µg; vitamin B12 2.2 µg; thiamine, riboflavin and niacin set per 1,000 kcal. Values differ between the 2010 and 2020 editions — always state which edition is being quoted.

Protein quality, digestibility and bioavailability

• Quality depends on the amino-acid pattern (how closely it matches human needs) and digestibility. Egg and milk are reference proteins; cereals are limiting in lysine, pulses in methionine/cysteine, maize in lysine and tryptophan.
• Mutual supplementation (complementation): cereal + pulse together (idli, khichdi, dal–chawal, roti–dal) gives a better amino-acid score than either alone — typically 3–4 parts cereal to 1 part pulse.
• Measures: chemical/amino-acid score, PER (growth per g protein fed), BV (nitrogen retained ÷ nitrogen absorbed), true digestibility (TD), NPU (= BV × TD), net protein ratio, PDCAAS (capped at 1.00) and the newer DIAAS (ileal digestibility of each amino acid, not capped) recommended by FAO 2013.
• Nitrogen balance: positive in growth, pregnancy and recovery; negative in trauma, burns, fever and starvation; zero in healthy maintenance.
• Nitrogen-to-protein factor: 6.25 generally (16% N), 6.38 for milk, 5.70 for wheat, 5.95 for rice — the Kjeldahl basis for label protein.
• Bioavailability is reduced by antinutritional factors: phytate (binds iron, zinc, calcium), oxalate (binds calcium — spinach), tannins and polyphenols (inhibit non-haem iron), trypsin inhibitors and lectins (legumes), goitrogens (cabbage, cassava), avidin (raw egg white, binds biotin).
• Reduced by processing: soaking, germination, fermentation (phytase action), dehulling, cooking. Enhancers: vitamin C and animal "meat factor" for non-haem iron; vitamin D and lactose for calcium; fat for carotenoids and fat-soluble vitamins.
• Haem iron (meat, liver) is 15–35% absorbed; non-haem iron (cereals, pulses, greens) only 2–10% — the core reason India's anaemia burden persists on a largely vegetarian diet.

Vitamins and minerals — roles and deficiency

• Fat-soluble (A, D, E, K): absorbed with dietary fat, stored in liver and adipose tissue, excreted slowly → toxicity risk; need not be eaten daily.
• Water-soluble (B-complex, C): not stored (except B12 in liver, ~3–5 years), excess excreted in urine → daily intake needed, toxicity rare.
• Vitamin A (retinol; β-carotene is provitamin): vision, epithelial integrity, immunity. Deficiency → night blindness, Bitot's spots, xerophthalmia, keratomalacia. India runs biannual vitamin A supplementation for 9–59 months.
• Vitamin D (calciferol, made in skin from sunlight): calcium absorption. Deficiency → rickets in children, osteomalacia in adults; widespread in urban India despite sunshine.
• Vitamin E (tocopherols): antioxidant, protects membrane PUFA. Vitamin K: prothrombin synthesis; given to newborns.
• Thiamine (B1) – beriberi, Wernicke's encephalopathy; riboflavin (B2) – angular stomatitis, cheilosis, glossitis; niacin (B3) – pellagra (dermatitis, diarrhoea, dementia; classically in maize eaters, as its niacin is bound and tryptophan is low); pyridoxine (B6) – peripheral neuritis; folate – megaloblastic anaemia, neural tube defects (hence preconception supplementation); B12 – megaloblastic anaemia plus neurological damage, common in strict vegetarians; vitamin C – scurvy, poor wound healing, and it boosts iron absorption.
• Minerals: macro (Ca, P, Mg, Na, K, Cl, S) and trace (Fe, Zn, I, Cu, Se, Mn, Cr, Mo, F). Iron – anaemia; iodine – goitre, cretinism, IDD; zinc – growth failure, diarrhoea, poor wound healing; calcium/phosphorus – bone and tooth mineralisation; sodium/potassium – fluid balance, nerve conduction (excess sodium → hypertension); fluoride – caries protection at ~1 ppm, fluorosis above ~1.5 ppm in drinking water (an endemic problem in parts of Rajasthan, Gujarat, Andhra Pradesh, Telangana).

Balanced diet, food groups and life-stage needs

• Balanced diet: provides all nutrients in required amounts and proportions, with a small margin of safety, from foods that are affordable, available and acceptable.
• ICMR five food groups: (1) cereals, millets and their products; (2) pulses, legumes, nuts and oilseeds; (3) milk, meat, fish and eggs; (4) fruits and vegetables; (5) fats, oils and sugars.
• "My Plate for the Day" (ICMR–NIN, 2024): vegetables and fruits together take the largest share (about 400 g vegetables + 100 g fruit/day for a 2,000 kcal diet), cereals and millets reduced, pulses/eggs/flesh foods and nuts/seeds increased, visible fat and sugar restricted.
• Nutrient density (nutrient per 100 kcal) is the right criterion for the poor and for small children, whose stomach capacity limits bulk; energy density (kcal/g) matters for infant feeding and for obesity.
• Life stages: infancy — exclusive breastfeeding for 6 months, complementary feeding from 6 months, continued breastfeeding to 2 years; childhood and adolescence — highest needs per kg for growth, peak bone mass; pregnancy — +350 kcal, +7.6–17.6 g protein by trimester, iron-folic acid supplementation; lactation — +600 kcal and extra calcium; elderly — lower energy but same or higher protein, calcium, B12 and vitamin D.
• Glycaemic index/load rank carbohydrate foods by blood-glucose response; low-GI eating is central to diabetes diet counselling, a large and growing Indian application.

Malnutrition, Indian programmes and the regulations

• Malnutrition = undernutrition + overnutrition + micronutrient deficiency; India carries all three together ("double/triple burden").
• Anthropometric indicators (WHO 2006 standards, used in NFHS): stunting (low height-for-age, chronic), wasting (low weight-for-height, acute), underweight (low weight-for-age), MUAC and oedema for severe acute malnutrition.
• PEM: kwashiorkor — protein deficiency with adequate-ish energy: oedema, fatty liver, flaky-paint dermatosis, hair changes, apathy, weight may look normal; marasmus — severe energy deficit: gross wasting, no oedema, "old man's face", alert but irritable; marasmic kwashiorkor is mixed.
• Overnutrition: overweight, obesity, metabolic syndrome, type 2 diabetes, hypertension, dyslipidaemia. Indian/Asian BMI cut-offs are lower — overweight ≥ 23, obesity ≥ 25 kg/m² — with waist circumference ≥ 90 cm (men) and ≥ 80 cm (women) indicating abdominal obesity.
• Programmes: ICDS/Anganwadi, PM POSHAN (the mid-day meal scheme, renamed 2021), POSHAN Abhiyaan (National Nutrition Mission), Anaemia Mukt Bharat (6×6×6 strategy), weekly iron–folic acid supplementation, National Iodine Deficiency Disorders Control Programme, Pradhan Mantri Matru Vandana Yojana, Eat Right India (FSSAI).
• Fortification: Food Safety and Standards (Fortification of Foods) Regulations, 2018 set standards for salt (iodine, and double-fortified salt with iron), wheat flour and rice (iron, folic acid, B12), milk and edible oil (vitamins A and D), with the +F logo. Iodised salt must carry not less than 30 ppm iodine at manufacture and 15 ppm at retail. Mandatory/voluntary status varies by commodity — iodised salt for human consumption is mandatory; check the current amendment before quoting levels.
• Labelling: Food Safety and Standards (Labelling and Display) Regulations, 2020 require a nutritional information panel per 100 g / 100 ml and per serving, declaring energy (kcal), protein, carbohydrate (of which total sugars, added sugar), total fat, saturated fat, trans fat, cholesterol and sodium, plus % contribution to RDA per serve. Industrial trans fat is capped at 2% by mass of total oils and fats (FSSAI, in force from 1 January 2022).
• Claims: Food Safety and Standards (Advertising and Claims) Regulations, 2018 — e.g. "source of" a vitamin/mineral = ≥ 15% RDA per 100 g (solid) or ≥ 7.5% per 100 ml (liquid), "high in" = twice that; "source of protein" = ≥ 10% of energy from protein, "high protein" = ≥ 20%; "low fat" ≤ 3 g/100 g, "fat free" ≤ 0.5 g/100 g; "low sugar" ≤ 5 g/100 g, "sugar free" ≤ 0.5 g/100 g; "low sodium" ≤ 0.12 g/100 g. Thresholds sit in Schedule I and are amended — verify against the current text.
• Front-of-pack labelling (the proposed Indian Nutrition Rating star system) has been drafted but is not notified as final at the time of writing.

Key points

• Nutrient – a food chemical needed for energy, structure or regulation; six classes, of which carbohydrate, fat and protein yield energy.
• Atwater factors – 4, 4, 9 kcal/g for carbohydrate, protein and fat; 7 for alcohol, ~2 for fibre.
• 1 kcal = 4.184 kJ; energy of food is metabolisable, not gross, energy.
• BMR – resting energy for vital functions, 60–75% of TEE; driven mainly by lean body mass.
• TEE = BMR × PAL; PAL ≈ 1.53 (sedentary), 1.8 (moderate), 2.2+ (heavy).
• RQ – CO₂/O₂ ratio; 1.0 carbohydrate, 0.7 fat, ~0.85 mixed diet.
• EAR meets 50% of a group's needs; RDA = EAR + 2 SD, meets 97.5%; energy has no RDA.
• TUL – upper safe chronic intake, the limit that matters for fortification and supplements.
• Protein RDA (ICMR–NIN 2020) – EAR 0.83 g/kg/day → ~54 g (man, 65 kg), ~46 g (woman, 55 kg).
• Limiting amino acids – lysine in cereals, methionine in pulses; cereal–pulse mixing corrects both.
• NPU = BV × TD/100; PDCAAS capped at 1.00, DIAAS is the FAO-preferred successor.
• Haem iron 15–35% absorbed vs non-haem 2–10%; vitamin C raises, phytate and tannin lower, absorption.
• Fat-soluble vitamins (A, D, E, K) are stored and can be toxic; water-soluble ones need daily intake.
• Kwashiorkor = oedema, marasmus = wasting without oedema — the single most-tested distinction.
• Asian BMI cut-offs – overweight ≥ 23, obese ≥ 25 kg/m²; waist ≥ 90 cm (M) / ≥ 80 cm (F).
• Stunting = height-for-age, wasting = weight-for-height (chronic vs acute undernutrition).
• FSSAI governs fortification (2018, +F logo), labelling (2020, per 100 g + %RDA) and claims (2018); industrial trans fat capped at 2%.
• Balanced diet – all nutrients in right proportion with a safety margin, from affordable, acceptable foods.

Formulas and examples

Example 1 — energy of a packaged biscuit and its fat share. Per 100 g: protein 7 g, available carbohydrate 65 g, fat 20 g, dietary fibre 3 g.

• Carbohydrate: 65 × 4 = 260 kcal; protein: 7 × 4 = 28 kcal; fat: 20 × 9 = 180 kcal.
• Subtotal = 260 + 28 + 180 = 468 kcal; adding fibre at 2 kcal/g (3 × 2 = 6) gives 474 kcal/100 g.
• % energy from fat = 180 ÷ 468 × 100 = 38.5% — above the 20–30% guideline, so this is a high-fat snack.
• A 30 g serving = 468 × 0.30 ≈ 140 kcal; against a 2,000 kcal diet that is 7% of energy per serving.

Example 2 — BMI, BMR and daily energy need. Man, 30 years, 72 kg, 1.70 m, desk job (sedentary).

• BMI = 72 ÷ (1.70²) = 72 ÷ 2.89 = 24.9 kg/m² → normal by the WHO cut-off (18.5–24.9) but overweight by the Asian cut-off (≥ 23).
• BMR = 10(72) + 6.25(170) − 5(30) + 5 = 720 + 1,062.5 − 150 + 5 = 1,637.5 kcal/day.
• TEE = 1,637.5 × 1.53 = ≈ 2,505 kcal/day.
• Protein goal at 0.83 g/kg EAR → RDA basis ≈ 1.0 g/kg = ~72 g/day; fat at 25% of energy = 0.25 × 2,505 ÷ 9 = ~70 g/day total fat.

Example 3 — nitrogen balance. A patient takes 70 g protein/day; urinary N 9.0 g, faecal N 1.2 g, dermal N 0.3 g.

• N intake = 70 ÷ 6.25 = 11.2 g N/day; total losses = 9.0 + 1.2 + 0.3 = 10.5 g N/day.
• Balance = 11.2 − 10.5 = +0.7 g N/day → positive; as protein, 0.7 × 6.25 = +4.4 g protein/day retained, consistent with anabolism/recovery.

Example 4 — TD, BV and NPU of a test protein. N intake I = 10.0 g; faecal N F = 1.5 g, metabolic faecal N F_k = 0.5 g; urinary N U = 3.5 g, endogenous urinary N U_e = 0.6 g.

• TD = [10.0 − (1.5 − 0.5)] ÷ 10.0 × 100 = 9.0 ÷ 10.0 × 100 = 90%; N absorbed = 9.0 g.
• BV = [9.0 − (3.5 − 0.6)] ÷ 9.0 × 100 = (9.0 − 2.9) ÷ 9.0 × 100 = 6.1 ÷ 9.0 × 100 = 67.8%.
• NPU = 67.8 × 90 ÷ 100 = 61.0% — a cereal-type protein, well below egg (BV ~94, NPU ~91).

Example 5 — glycaemic load and a label claim check.

• A 150 g serving of cooked white rice supplies 40 g available carbohydrate; GI = 73. GL = 73 × 40 ÷ 100 = 29.2 → high (GL ≥ 20 is high). Replacing half with dal/vegetables to give 25 g carbohydrate drops GL to 73 × 25 ÷ 100 = 18.3 → medium.
• A flavoured milk provides 200 mg calcium per 100 ml. % RDA = 200 ÷ 1,000 × 100 = 20%. For a liquid, "source" needs ≥ 7.5% and "high" ≥ 15% of RDA per 100 ml → the claim "high in calcium" is supportable under the 2018 Claims Regulations.

Where it is used

• Food product development and QA: computing label nutrition panels, %RDA per serve, reformulating to meet the 2% trans-fat cap or to earn a "high protein"/"low sodium" claim — roles at Nestlé India, ITC Foods, Britannia, HUL, Mondelez, Amul, Hatsun.
• Regulatory and labelling affairs: FSSAI licence dossiers, nutrition claims vetting, fortification compliance (+F logo), proprietary-food and nutraceutical approvals; Food Safety Officer and FSSAI Technical Officer posts.
• Clinical and community dietetics: diet charts by BMR × PAL, exchange lists, low-GI diabetic diets, renal and paediatric diets in hospitals; RD registration through the Indian Dietetic Association.
• Public-health nutrition: ICDS/Anganwadi take-home rations, PM POSHAN menu costing and nutrient calculation, Anaemia Mukt Bharat, NFHS and CNNS survey analysis, FSSAI Eat Right campus audits.
• Fortified-staple industry: fortified rice kernels (FRK), double-fortified salt, fortified atta and oil for PDS and mid-day meals — premix dosing, assay and shelf-stability work.
• Food analysis laboratories: proximate analysis, Kjeldahl nitrogen, bomb calorimetry, vitamin and mineral assays for label verification under NABL and FSSAI-notified labs.
• Sports and wellness nutrition, and food-tech content roles: protein targets per kg body weight, supplement label review, calorie-counting app databases built on IFCT 2017 food-composition values.

Interview questions

• Q: Why does protein give 4 kcal/g when its gross energy is about 5.65 kcal/g? A: Nitrogen cannot be oxidised in the body and is excreted as urea and other nitrogenous compounds, carrying away roughly 1.25 kcal/g; digestibility losses account for the remainder.
• Q: What is the difference between EAR and RDA, and which one do you use for an individual? A: EAR meets the requirement of 50% of a healthy group; RDA is EAR + 2 SD and meets 97.5%. RDA is the goal for an individual, EAR for assessing or planning for groups.
• Q: Why is there no RDA for energy? A: Energy requirement is symmetrically distributed and excess is stored as fat, so recommending average + 2 SD would promote obesity; the average requirement is used instead.
• Q: How do you distinguish kwashiorkor from marasmus clinically? A: Kwashiorkor shows pitting oedema, fatty liver, dermatosis and apathy with weight partly masked; marasmus shows severe wasting without oedema and the child is usually hungry and alert.
• Q: Why is anaemia so common in India despite diets rich in green leafy vegetables? A: Plant iron is non-haem and only 2–10% absorbed, and phytates, tannins, oxalates and calcium in the same meal further inhibit it; low vitamin C intake at the meal compounds the problem.
• Q: What is NPU and why is it better than BV? A: NPU = BV × true digestibility; BV only measures retention of the nitrogen that was absorbed, whereas NPU also penalises a protein that is poorly digested.
• Q: Explain mutual supplementation with an Indian example. A: Cereals lack lysine and pulses lack methionine, so combining them — dal–chawal, idli, khichdi — gives a near-complete amino-acid pattern; about 3–4 parts cereal to 1 part pulse.
• Q: Why are Asian BMI cut-offs lower than WHO's? A: At the same BMI, Indians carry more body fat and more visceral fat and show cardiometabolic risk earlier, so overweight is set at ≥ 23 and obesity at ≥ 25 kg/m².
• Q: What must appear in the nutritional information panel of a packaged food in India? A: Under the Labelling and Display Regulations, 2020 — energy, protein, carbohydrate with total and added sugars, total fat, saturated fat, trans fat, cholesterol and sodium, per 100 g/100 ml and per serve, with % RDA contribution per serve.
• Q: Which nutrients are mandated in fortified wheat flour and rice in India? A: Iron, folic acid and vitamin B12 under the Fortification of Foods Regulations, 2018, carried with the +F logo; iodised salt and double-fortified salt and vitamin A and D in oil and milk are the other main vehicles.
• Q: What is RQ and what is its practical use? A: The ratio of CO₂ produced to O₂ consumed — 1.0 for carbohydrate, 0.7 for fat, about 0.85 on a mixed diet — used in indirect calorimetry to work out which substrate is being oxidised and the energy expenditure.
• Q: A product claims "sugar free" but tastes sweet and has 420 kcal/100 g. Is that legal? A: Yes, if total sugars are ≤ 0.5 g/100 g; the sweetness can come from permitted sweeteners or polyols, and "sugar free" says nothing about energy — the claim must not imply low calorie.
• Q: Why can a vitamin A overdose harm but a vitamin C overdose rarely does? A: Vitamin A is fat-soluble and stored in the liver, so chronic excess accumulates and is teratogenic and hepatotoxic; vitamin C is water-soluble and the excess is excreted in urine.

Common mistakes

• Using 9 kcal/g for protein or 4 for fat, or forgetting that the carbohydrate figure in a label calculation must be available carbohydrate, with fibre counted separately at ~2 kcal/g.
• Treating RDA as a minimum requirement and calling any intake below it a deficiency, or using RDA where EAR is the correct tool for group assessment.
• Quoting ICMR RDA values without saying which edition — the 2020 figures differ from 2010 (reference man 65 kg, protein, vitamin C, iron and calcium all changed).
• Mixing units in BMR formulas: Mifflin–St Jeor needs height in centimetres, while BMI needs height in metres — a frequent source of absurd answers.
• Confusing stunting with wasting, or reporting a BMI as normal using WHO cut-offs when the Asian cut-off of 23 applies to an Indian subject.
• Forgetting metabolic faecal nitrogen and endogenous urinary nitrogen in TD and BV calculations, which inflates both values.
• Saying "protein quality" means protein quantity, or claiming a single plant food is a "complete protein" without checking its limiting amino acid.
• Quoting fortification or claim thresholds from an old FSSAI circular — these schedules are amended frequently and must be checked against the current notification.

Related topics

Food chemistry: carbohydrates, proteins and fats · Food additives · Food microbiology · Food analysis and proximate composition · Food fortification and nutraceuticals · Diet therapy and clinical nutrition · FSSAI food safety law and labelling