Nutritional biochemistry

In short

Nutritional biochemistry studies how nutrients in food are digested, absorbed, metabolised and used to meet energy, growth and regulatory needs, and what happens biochemically when they are deficient or in excess. It links classical metabolism (glycolysis, β-oxidation, urea cycle) to practical numbers: energy requirements, protein quality, recommended dietary allowances and deficiency diseases. It is a core paper in B.Sc/M.Sc Biochemistry, Food Technology and Nutrition courses, and is examined in CSIR-UGC NET (Life Sciences), GATE Biotechnology/XL, ICMR-JRF and FSSAI/food-industry recruitment. In India the applied side runs on ICMR-NIN Recommended Dietary Allowances (latest revision 2020) and FSSAI standards under the Food Safety and Standards Act, 2006 — used daily in food companies, hospital dietetics, nutraceutical QC and public-health programmes.

Explained

Nutrients, energy value of food and energy balance

• Nutrient classes: macronutrients (carbohydrate, protein, fat, water) supply energy and structure; micronutrients (13 vitamins, ~15 essential minerals) act as coenzymes, cofactors, antioxidants and signalling molecules. Essential nutrient = one the body cannot synthesise at all or fast enough, so it must come from diet.
• Gross energy is measured in a bomb calorimeter; physiological (metabolisable) energy subtracts faecal, urinary and surface losses. Practical Atwater factors: carbohydrate 4, protein 4, fat 9, alcohol 7, dietary fibre ~2, polyols ~2.4 kcal/g (1 kcal = 4.184 kJ).
• Protein loses most between gross and net value (~5.65 → 4 kcal/g) because nitrogen is excreted as urea, not oxidised.
• Components of total energy expenditure (TEE): basal metabolic rate (BMR, 60–70%), thermic effect of food / specific dynamic action (SDA, ~10% of intake — protein 20–30%, carbohydrate 5–10%, fat 0–3%), physical activity (15–30%), plus growth, pregnancy, lactation, thermoregulation.
• BMR depends on lean body mass, surface area, age (falls ~2% per decade in adults), sex (lower in women), thyroid hormones (T3 raises it), fever (+13% per °C), and falls 10–20% in chronic undernutrition (metabolic adaptation).
• ICMR-NIN 2020 expresses requirements for a reference man (65 kg) and woman (55 kg) by physical activity level (PAL): roughly 2,110 / 1,660 kcal sedentary, 2,710 / 2,130 kcal moderate, and higher for heavy work; exact tables should be read from the current ICMR-NIN publication, as the 2020 revision actually lowered the energy and protein figures of the 2010 edition (sedentary man 2,320 → 2,110 kcal; protein 1.0 → 0.83 g/kg/day) while raising several micronutrient values.
• Energy balance: intake = expenditure ± storage. A sustained surplus is stored mainly as triacylglycerol (~7,700 kcal per kg of adipose tissue); deficit mobilises glycogen, then fat, then muscle protein.

Carbohydrates, lipids and fibre in nutrition

• Available carbohydrate: starch, sucrose, lactose, glucose — digested to monosaccharides, absorbed by SGLT1 (Na⁺-dependent, glucose/galactose) and GLUT5 (fructose). Recommended as 50–60% of energy; added sugar should stay below ~10% (ICMR-NIN dietary guidelines, 2024, advise ≤5% ideally).
• No carbohydrate is strictly "essential", but ~100–130 g/day prevents ketosis; brain needs ~120 g glucose/day, red cells and renal medulla are glucose-dependent.
• Dietary fibre: non-starch polysaccharides + lignin. Soluble (pectin, β-glucan, gums) lowers LDL and slows glucose absorption; insoluble (cellulose, hemicellulose) adds bulk and speeds transit. Fermented by colonic bacteria to short-chain fatty acids (acetate, propionate, butyrate — butyrate is the colonocyte's main fuel). ICMR-NIN suggests about 30 g/2,000 kcal.
• Glycemic index (GI) = blood-glucose response to 50 g available carbohydrate of a food relative to glucose (or white bread) = 100. Glycemic load accounts for portion size. Low-GI diets help type-2 diabetes management; Indian staples: parboiled rice and whole dals are lower-GI than polished rice or refined wheat.
• Lipids: supply 20–30% of energy (ICMR-NIN: visible fat 25–30 g/day for a sedentary adult, more for heavy work). Roles — energy store, membrane phospholipids, carrier of vitamins A, D, E, K, precursors of eicosanoids.
• Essential fatty acids: linoleic acid (18:2, n-6) and α-linolenic acid (18:3, n-3) — humans lack Δ12 and Δ15 desaturases. Deficiency causes dermatitis, poor growth and impaired wound healing. Desired n-6 : n-3 ratio roughly 5–10 : 1; Indian diets are usually n-6 heavy, so mustard, flaxseed and soybean oil or fish improve the ratio. EPA/DHA support retinal and neural function.
• Trans fatty acids raise LDL and lower HDL; FSSAI caps industrial trans fat at 2% by mass of total oils and fats (effective January 2022). Saturated fat should be <10% of energy, cholesterol intake moderate (~300 mg/day).

Proteins, amino acids and protein quality

• Nine indispensable amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine. Conditionally essential: arginine, cysteine, tyrosine, glutamine, proline, glycine (in infants, trauma, liver disease).
• ICMR-NIN 2020 RDA for protein: about 0.83 g/kg/day of good-quality protein for adults (safe level), higher in pregnancy, lactation, growth and illness; Indian diets being cereal-pulse based, quality correction matters.
• Nitrogen balance: proteins average 16% N → multiply N by 6.25 for protein. Positive in growth, pregnancy and recovery; negative in trauma, burns, infection, starvation and immobilisation.
• Protein quality measures: chemical (amino acid) score; PER (protein efficiency ratio, rat growth per g protein); BV (biological value = N retained/N absorbed, egg = 100); NPU = BV × digestibility; PDCAAS (FAO/WHO 1991, truncated to 1.0); DIAAS (FAO 2013, based on ileal digestibility of individual amino acids, not truncated) is the current recommended index.
• Limiting amino acids: cereals — lysine (and threonine); pulses and legumes — methionine/cysteine; maize — lysine and tryptophan (hence pellagra risk). Mutual supplementation: cereal + pulse in roughly 4:1 by protein gives a near-complete pattern — the biochemical basis of dal-chawal, khichdi, idli (rice + black gram) and PM POSHAN menus.
• Protein-sparing action of carbohydrate: adequate energy prevents dietary amino acids from being burnt for fuel; this is why energy deficit worsens protein deficiency.
• Anti-nutritional factors lower protein and mineral value: trypsin inhibitors and lectins (legumes — destroyed by heat), phytate (binds Fe, Zn, Ca), tannins, oxalate, goitrogens, lathyrogen BOAA in Lathyrus sativus (khesari dal). Soaking, germination, fermentation and cooking reduce them.

Vitamins: biochemical roles and deficiency syndromes

• Water-soluble (coenzyme roles): B1 thiamine → TPP (pyruvate and α-ketoglutarate dehydrogenase, transketolase) — deficiency: beriberi, Wernicke–Korsakoff; B2 riboflavin → FMN/FAD — angular stomatitis, cheilosis, glossitis; B3 niacin → NAD⁺/NADP⁺ (made from tryptophan, 60 mg Trp ≈ 1 mg niacin) — pellagra (dermatitis, diarrhoea, dementia); B5 → coenzyme A; B6 pyridoxine → PLP (transamination, decarboxylation, ALA synthase) — peripheral neuropathy, sideroblastic anaemia, isoniazid-induced deficiency; biotin → carboxylases (acetyl-CoA, pyruvate carboxylase); folate → THF, one-carbon transfer — megaloblastic anaemia, neural tube defects; B12 → methylmalonyl-CoA mutase and methionine synthase — megaloblastic anaemia with neurological signs, common in Indian vegetarians; vitamin C → collagen hydroxylation, non-haem iron absorption, antioxidant — scurvy.
• Fat-soluble: A (retinol/retinal/retinoic acid) — rhodopsin, epithelial differentiation, gene regulation; deficiency: night blindness, Bitot's spots, xerophthalmia, keratomalacia. D (calcitriol) — calcium and phosphate absorption via calbindin; rickets, osteomalacia; very widespread insufficiency in India despite sunlight. E (α-tocopherol) — membrane antioxidant; haemolysis in preterm infants. K — γ-carboxylation of clotting factors II, VII, IX, X and osteocalcin; haemorrhagic disease of the newborn.
• Toxicity is a real risk for fat-soluble vitamins (hypervitaminosis A: raised intracranial pressure, teratogenicity; vitamin D: hypercalcaemia) and for high-dose B6 (neuropathy) and iron supplements.
• Indicative ICMR-NIN 2020 adult RDAs (verify against the current table): vitamin C ~80 mg, folate ~300 µg, B12 ~2.2 µg, vitamin A ~1,000 µg RAE (men) / 840 µg (women), vitamin D ~600 IU (15 µg), calcium ~1,000 mg, iron ~19 mg (men) / 29 mg (women of reproductive age), zinc ~17 mg / 13 mg, iodine 150 µg.

Minerals, bioavailability and water

• Macrominerals: calcium (bone hydroxyapatite, signalling; absorption needs calcitriol, helped by lactose, hindered by phytate and oxalate), phosphorus, magnesium (cofactor for all kinases/ATP), sodium, potassium, chloride, sulphur.
• Trace elements: iron (haem, cytochromes), zinc (>300 enzymes, carbonic anhydrase, DNA-binding zinc fingers), copper (cytochrome c oxidase, ceruloplasmin, lysyl oxidase), iodine (T3/T4; deficiency → goitre, cretinism), selenium (glutathione peroxidase, deiodinases), manganese, molybdenum, chromium, fluoride (dental caries protection; excess → fluorosis, endemic in parts of Rajasthan, Andhra Pradesh, Telangana).
• Iron forms and bioavailability: haem iron (meat, ~20–25% absorbed) vs non-haem (plant, 1–10%). Enhancers — vitamin C, meat/fish factor, germination, fermentation. Inhibitors — phytate, polyphenols in tea and coffee, calcium, excess fibre. ICMR-NIN 2020 assumes about 8% bioavailability for typical Indian diets, which is why the iron RDA looks high.
• Regulation of iron: hepcidin from liver blocks ferroportin, reducing absorption and macrophage release; ferritin stores, transferrin transports. Anaemia of inflammation differs biochemically from iron-deficiency anaemia (both low Hb, but ferritin is low in deficiency, normal/high in inflammation).
• Water and electrolytes: 50–60% of adult body weight; balance of intake, metabolic water (~300 mL/day) and losses (urine, insensible, faecal); controlled by ADH, aldosterone and thirst.

Metabolic integration: fed, fasting and malnourished states

• Fed (absorptive) state: insulin high — glycogenesis, lipogenesis, protein synthesis, GLUT4 recruitment in muscle and adipose.
• Early fasting (up to ~18 h): glucagon and adrenaline rise — hepatic glycogenolysis supplies glucose; liver glycogen (~100 g) is exhausted in about a day.
• Fasting/starvation: gluconeogenesis from lactate, glycerol and amino acids (alanine and glutamine from muscle); lipolysis supplies free fatty acids; after ~3 days ketone bodies (acetoacetate, β-hydroxybutyrate) fuel the brain, sparing protein. Nitrogen excretion falls from ~12 g/day to ~4 g/day — the biochemical adaptation that prolongs survival.
• Protein–energy malnutrition (PEM): marasmus — severe energy deficit, marked wasting, weight-for-height very low, no oedema, relatively preserved albumin; kwashiorkor — relatively greater protein deficit with oedema, fatty liver (apolipoprotein synthesis fails, so VLDL export stops), hypoalbuminaemia, skin and hair changes, often triggered by infection and oxidative stress. Marasmic-kwashiorkor is mixed.
• Refeeding syndrome: rapid carbohydrate feeding of a starved patient drives insulin-mediated intracellular shift of phosphate, potassium and magnesium plus thiamine consumption — arrhythmia and death; refeed slowly with thiamine and electrolytes (basis of WHO/NRC F-75 then F-100 therapeutic diets used in Indian Nutrition Rehabilitation Centres).
• Overnutrition: positive energy balance → adipocyte hypertrophy, insulin resistance, dyslipidaemia, non-alcoholic fatty liver, metabolic syndrome. Indians show a "thin-fat" phenotype — higher body fat and visceral fat at a given BMI — hence lower Asian-Indian cut-offs.

Assessment of nutritional status, Indian standards and programmes

• ABCD of assessment: Anthropometry (weight, height, BMI, mid-upper arm circumference, skinfolds, waist circumference); Biochemical (Hb, serum ferritin, albumin/prealbumin, retinol, 25-OH vitamin D, urinary iodine, nitrogen balance); Clinical signs; Dietary survey (24-h recall, food frequency, weighment method).
• Classification tools: WHO growth standards and z-scores (stunting = height-for-age < −2 SD; wasting = weight-for-height < −2 SD; underweight = weight-for-age < −2 SD); Gomez and IAP classifications; MUAC < 11.5 cm in 6–59 months = severe acute malnutrition.
• BMI cut-offs: WHO global — overweight ≥25, obese ≥30; Asian-Indian/ICMR consensus — overweight 23.0–24.9, obese ≥25, with waist circumference action levels around 90 cm (men) and 80 cm (women).
• Regulation and law: the Food Safety and Standards Act, 2006 and FSSAI regulations govern food standards, additives, claims and labelling. The Food Safety and Standards (Labelling and Display) Regulations, 2020 require nutrition declaration per 100 g/100 mL (and per serve) of energy, protein, carbohydrate with total sugars and added sugars, total fat, saturated and trans fat, sodium, plus % contribution to RDA. The Fortification of Foods Regulations, 2018 set standards and the "+F" logo for iodised/double-fortified salt, fortified wheat flour and rice (iron, folic acid, B12), and fortified edible oil and milk (vitamins A and D). Iodised salt must carry not less than 15 ppm iodine at the consumer end (30 ppm at manufacture).
• National programmes: POSHAN Abhiyaan and Poshan 2.0, ICDS/Anganwadi supplementary nutrition, PM POSHAN (mid-day meal), Anaemia Mukt Bharat (6×6×6 strategy, weekly iron-folic acid supplementation), vitamin A prophylaxis (9 months to 5 years), National Iodine Deficiency Disorders Control Programme, and rice fortification in public distribution schemes. NFHS-5 (2019–21) recorded anaemia in 57% of women aged 15–49 and 67% of children 6–59 months, stunting 35.5%, wasting 19.3%, with rising adult overweight — later survey rounds may revise these figures.

Key points

• Atwater factors - metabolisable energy 4 kcal/g carbohydrate and protein, 9 fat, 7 alcohol, ~2 fibre.
• BMR - energy at complete rest, post-absorptive, thermoneutral; 60–70% of TEE, driven by lean mass and thyroid status.
• SDA/thermic effect - ~10% of a mixed diet's energy; highest for protein (20–30%).
• Nitrogen factor 6.25 - proteins are ~16% nitrogen; nitrogen balance measures protein adequacy.
• Essential amino acids - nine indispensable; cereals limit lysine, pulses limit methionine, so they complement each other.
• Protein quality order - egg/milk > meat/fish > soy > pulses > cereals, by BV, NPU, PDCAAS and now DIAAS.
• ICMR-NIN 2020 protein RDA - about 0.83 g/kg/day for adults, raised in growth, pregnancy and illness.
• Essential fatty acids - linoleic (n-6) and α-linolenic (n-3); humans lack Δ12/Δ15 desaturases.
• Trans fat limit - FSSAI caps industrial trans fat at 2% by mass of oils and fats.
• Fibre - soluble lowers cholesterol and glycemic response; insoluble adds bulk; colonic fermentation yields butyrate.
• Water-soluble vitamins are coenzymes - TPP, FAD, NAD⁺, CoA, PLP, biotin, THF, cobalamin; little storage except B12 and folate.
• Fat-soluble vitamins - A, D, E, K; stored, need bile and fat for absorption, and can be toxic in excess.
• Iron bioavailability - haem 20–25%, non-haem 1–10%; vitamin C enhances, phytate and tannins inhibit; hepcidin controls absorption.
• PEM - marasmus is energy-dominant wasting; kwashiorkor adds oedema and fatty liver from failed lipoprotein export.
• Starvation adaptation - glycogen → gluconeogenesis → ketone bodies, with nitrogen excretion falling to spare protein.
• Asian-Indian BMI cut-offs - overweight ≥23, obese ≥25; waist ≥90 cm (men), ≥80 cm (women).
• Assessment - ABCD: anthropometry, biochemical, clinical, dietary.
• Regulator - FSSAI under the FSS Act, 2006; 2020 labelling and 2018 fortification regulations give the Indian compliance framework.

Formulas and examples

1. Energy value and label declaration. A packaged namkeen contains per 100 g: carbohydrate 60 g (of which added sugar 3 g), protein 10 g, fat 25 g, fibre 3 g.

• Energy = (60 × 4) + (10 × 4) + (25 × 9) + (3 × 2) = 240 + 40 + 225 + 6 = 511 kcal = 511 × 4.184 ≈ 2,138 kJ.
• Energy from fat = 225/511 = 44.0% — far above the 20–30% desirable range.
• A 30 g serve = 511 × 0.30 ≈ 153 kcal, i.e. about 7.3% of a 2,100 kcal sedentary-man requirement.

2. Nitrogen balance. A 60 kg adult consumes 60 g protein/day. Urinary N = 8.0 g, faecal N = 1.2 g, dermal/miscellaneous = 0.3 g.

• N intake = 60 / 6.25 = 9.6 g/day; total N loss = 8.0 + 1.2 + 0.3 = 9.5 g/day.
• Balance = +0.1 g N/day ≈ +0.6 g protein/day — essentially nitrogen equilibrium, so intake is just adequate.
• Intake per kg = 60/60 = 1.0 g/kg/day, above the 0.83 g/kg safe level.

3. PDCAAS of wheat protein. Lysine content 25 mg/g protein; reference requirement pattern 48 mg lysine/g protein; true digestibility 0.87.

• Amino acid score = 25/48 = 0.52; PDCAAS = 0.52 × 0.87 = 0.45.
• Blending with a pulse (lysine ~64 mg/g protein) raises the limiting amino acid: for a 4:1 wheat:dal protein mix, lysine = (4 × 25 + 1 × 64)/5 = 32.8 mg/g, score 32.8/48 = 0.68 — about a 31% improvement in protein quality (0.52 → 0.68) at no extra cost.

4. BMR, TEE and BMI. Male, 25 years, 72 kg, 168 cm, moderately active office worker who also plays sport (PAL 1.7).

• BMR = (10 × 72) + (6.25 × 168) − (5 × 25) + 5 = 720 + 1,050 − 125 + 5 = 1,650 kcal/day.
• TEE = 1,650 × 1.7 = 2,805 kcal/day.
• BMI = 72 / (1.68)² = 72 / 2.8224 = 25.5 kg/m² → obese by Asian-Indian cut-offs (≥25) though only "overweight" by the WHO global cut-off.
• To lose 0.5 kg fat/week he needs a deficit of ~7,700 × 0.5 = 3,850 kcal/week ≈ 550 kcal/day, i.e. an intake of about 2,250 kcal/day.

5. Iron RDA from bioavailability. A menstruating woman's physiological requirement for absorbed iron is about 2.32 mg/day; Indian diets give ~8% absorption.

• RDA = 2.32 / 0.08 = 29 mg/day — the ICMR-NIN 2020 figure.
• If vitamin C-rich foods raise absorption to 12%, requirement = 2.32 / 0.12 ≈ 19 mg/day, a 34% lower dietary need — the biochemical argument for adding lemon or amla rather than tea to meals.

Where it is used

• Food processing and FMCG R&D (ITC, Nestlé India, Britannia, Amul, Hindustan Unilever): recipe formulation, nutrient profiling, shelf-life and label compliance under the FSS (Labelling and Display) Regulations, 2020.
• Food testing and QC laboratories (FSSAI-notified/NABL labs): proximate analysis (Kjeldahl nitrogen, Soxhlet fat, ash, moisture, fibre), vitamin and mineral assays by HPLC and AAS/ICP-MS, verification of fortification levels.
• Clinical nutrition and dietetics in hospitals: therapeutic diets for diabetes, renal and liver disease, enteral/parenteral nutrition, nitrogen balance in ICU patients, F-75/F-100 regimens in Nutrition Rehabilitation Centres.
• Public health and programme roles — NIN/ICMR, UNICEF, state nutrition missions: dietary surveys, anaemia and vitamin A programmes, rice-fortification monitoring in the public distribution system, POSHAN Tracker data.
• Nutraceutical and supplement industry (Himalaya, Dabur, Patanjali, contract manufacturers): formulation, bioavailability studies and claim substantiation under FSSAI's health supplements and nutraceuticals regulations.
• Sports and corporate wellness, and agri-biotech: energy/protein prescription for athletes; biofortified crops such as iron-rich pearl millet, zinc wheat and Golden Rice-type provitamin A lines.

Interview questions

• Q: Why is protein assigned 4 kcal/g when its heat of combustion is about 5.65 kcal/g? A: Nitrogen is excreted as urea rather than fully oxidised, and digestibility is incomplete; the difference is lost in urine and faeces.
• Q: What does a negative nitrogen balance indicate? A: Net loss of body protein — seen in inadequate protein or energy intake, trauma, burns, sepsis, uncontrolled diabetes and immobilisation.
• Q: Why is the Indian iron RDA for women as high as about 29 mg/day when absorbed need is ~2.3 mg? A: Because typical phytate- and tannin-rich Indian diets give only ~8% bioavailability, so the dietary allowance is the requirement divided by that fraction.
• Q: Which amino acid limits cereals and which limits pulses, and why does mixing help? A: Lysine limits cereals, methionine/cysteine limits pulses; combining them in roughly 4:1 protein ratio corrects both deficits — mutual supplementation.
• Q: How does DIAAS differ from PDCAAS? A: DIAAS uses true ileal digestibility of each individual amino acid and is not truncated at 1.0, so it discriminates better among high-quality proteins.
• Q: Explain the fatty liver of kwashiorkor biochemically. A: Protein deficiency limits apolipoprotein B synthesis, so triacylglycerol cannot be exported as VLDL and accumulates in hepatocytes.
• Q: Why do ketone bodies rise in prolonged fasting, and what is their benefit? A: Low insulin drives lipolysis and β-oxidation faster than the TCA cycle can handle acetyl-CoA; the brain adapts to β-hydroxybutyrate, which spares muscle protein and reduces gluconeogenic demand.
• Q: What is the respiratory quotient and what does an RQ of 0.7 tell you? A: The ratio of CO₂ produced to O₂ consumed; 0.7 indicates predominantly fat oxidation, as in fasting or a ketogenic state.
• Q: Why are the BMI cut-offs lower for Indians? A: At any given BMI, Indians have higher body fat and visceral adiposity and develop insulin resistance and dyslipidaemia earlier, so overweight starts at 23 and obesity at 25 kg/m².
• Q: Which nutrient interactions must be watched in a vegetarian Indian diet? A: Vitamin B12 (absent from plant foods), iron and zinc (phytate inhibition), vitamin D, and long-chain n-3 fatty acids.
• Q: What is refeeding syndrome and how is it prevented? A: Insulin-driven intracellular shift of phosphate, potassium and magnesium with thiamine depletion on rapid refeeding of a starved patient; prevented by slow calorie escalation with thiamine and electrolyte correction.
• Q: Under which Indian regulation is nutrition labelling mandatory, and what must be declared? A: The Food Safety and Standards (Labelling and Display) Regulations, 2020 — energy, protein, carbohydrate with total and added sugars, total fat, saturated and trans fat and sodium per 100 g/mL and per serve, with % RDA contribution.

Common mistakes

• Using gross calorific values from bomb calorimetry in place of Atwater metabolisable values, and ignoring the 1 kcal = 4.184 kJ conversion.
• Multiplying nitrogen by 6.5 or 6, or forgetting dermal/miscellaneous nitrogen (~0.3 g) in nitrogen-balance sums.
• Confusing BMR with total energy expenditure, or applying a PAL to TEE a second time.
• Calling niacin or vitamin D "essential in the absolute sense" without noting endogenous synthesis from tryptophan and from skin 7-dehydrocholesterol.
• Quoting WHO global BMI cut-offs for Indian subjects, or waist cut-offs of 102/88 cm instead of 90/80 cm.
• Describing kwashiorkor as pure protein deficiency and reversing the oedema/albumin findings between it and marasmus.
• Quoting pre-2020 ICMR RDA figures (the 2020 revision changed energy, protein, vitamin C, iron and several micronutrient values) or outdated FSSAI labelling limits.

Related topics

Clinical biochemistry: organ function tests · Carbohydrate and lipid metabolism · Enzymes, coenzymes and vitamins · Food chemistry and food analysis · Food microbiology and safety (FSSAI) · Endocrinology and metabolic regulation