Tamil Nadu HSE First Year Nutrition and Dietetics cheat sheet

Nutrition is the science of food, its nutrients, their action, interaction and balance in relation to health and disease; dietetics is the application of this science to feeding individuals and groups.

Nutrients are classed as macronutrients (carbohydrate, protein, fat - needed in gram quantities) and micronutrients (vitamins, minerals - needed in milligram or microgram quantities); water is an essential nutrient without energy value.

Essential nutrients cannot be synthesised in the body in adequate amounts and must come from diet: 9 amino acids, 2 fatty acids (linoleic, alpha-linolenic), 13 vitamins, and the mineral elements.

Scope of the field includes clinical dietetics, community nutrition, food service systems management, food science and quality control, research, and nutrition education.

Career roles: dietitian (registered, usually with a degree plus internship), nutritionist, public health nutritionist, food service manager, food technologist, nutrition educator, and research assistant.

Food provides three functions: physiological (energy, growth and repair, regulation of body processes), psychological (satisfaction, comfort, social bonding) and social/cultural (festivals, hospitality, religious practice).

In Tamil Nadu, nutrition and dietetics is taught at the Higher Secondary level as a vocational/home science subject; the professional degree route is B.Sc. Nutrition and Dietetics or Food Science and Nutrition.

Anthropometry (height, weight, BMI, MUAC), biochemical tests, clinical examination and dietary surveys are the four classic methods of nutritional assessment.

ICMR five food groups: cereals and millets; pulses and legumes; milk and meat products; fruits and vegetables; fats and sugars - a balanced diet draws from all five.

Functional classification by predominant nutrient: energy-giving (cereals, roots, fats, sugars), body-building (pulses, milk, egg, meat, fish), protective (fruits, vegetables, milk) and regulatory (water, fibre, minerals, vitamins).

Cereals supply 70-80% of dietary energy in Indian diets; they are limiting in lysine but rich in methionine-poor sulphur amino acids, so cereal-pulse combinations (idli, sambar rice, dal-rice) improve protein quality.

Pulses provide 20-25% protein, are rich in lysine but limiting in methionine; they also supply B vitamins and, when germinated, vitamin C.

Milk is a good source of calcium, riboflavin and high-quality protein but is a poor source of iron and vitamin C; it is deficient in vitamin D unless fortified.

Green leafy vegetables are the cheapest sources of beta-carotene, iron, calcium and folate; vitamin C is richest in amla, guava, citrus and sprouted pulses.

Foods are also classified as energy-dense (fats, sugars, refined cereals) versus nutrient-dense (millets, pulses, greens); nutrient density = nutrients per 100 kcal.

Anti-nutritional factors: phytic acid in cereals and legumes binds iron and zinc; oxalates in spinach reduce calcium absorption; tannins in tea reduce iron absorption; trypsin inhibitors in raw pulses are destroyed by cooking.

Carbohydrates yield 4 kcal/g; classified as monosaccharides (glucose, fructose), disaccharides (sucrose, lactose, maltose) and polysaccharides (starch, glycogen, cellulose, hemicellulose, pectin).

Dietary fibre: soluble fibre (pectin, gums, beta-glucan) lowers blood cholesterol and slows glucose absorption; insoluble fibre (cellulose, lignin) increases stool bulk and prevents constipation.

Protein yields 4 kcal/g; made of 20 amino acids, 9 essential (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine).

Protein quality measures: biological value (BV), net protein utilisation (NPU), protein efficiency ratio (PER), chemical score and PDCAAS; egg has BV near 94-100 and is the reference protein.

Protein functions: growth and repair of tissue, enzymes, hormones, antibodies, transport proteins (haemoglobin, albumin), osmotic balance, and energy when intake is excess or carbohydrate is inadequate.

Protein-energy malnutrition presents as marasmus (severe wasting, weight-for-age below 60% of reference, no oedema) and kwashiorkor (oedema, low serum albumin, hair and skin changes, often 1-3 years).

Lipids yield 9 kcal/g; classified as simple (triglycerides), compound (phospholipids, lipoproteins) and derived (fatty acids, sterols, fat-soluble vitamins).

Saturated fats (ghee, coconut oil, palm oil) raise LDL cholesterol; polyunsaturated fats (sunflower, safflower, soybean oil) lower LDL; trans fats from repeated deep frying and vanaspati raise LDL and lower HDL.

Essential fatty acid deficiency causes dermatitis, poor growth and impaired wound healing; visible fat intake should supply about 20-30% of total energy.

Fat-soluble vitamins: A, D, E, K - absorbed with dietary fat, stored in liver and adipose tissue, and toxic in excess; water-soluble vitamins B-complex and C are excreted in urine and need daily intake.

Vitamin A: retinol from liver, egg, milk and fish; beta-carotene from green leafy vegetables, carrot, papaya, mango. Deficiency causes night blindness, conjunctival xerosis, Bitot's spots, keratomalacia and growth retardation.

Vitamin D (calciferol): synthesised in skin on exposure to ultraviolet sunlight; deficiency causes rickets in children (bow legs, rachitic rosary) and osteomalacia in adults.

Thiamine (B1): deficiency causes beriberi - dry (peripheral neuritis) and wet (oedema, cardiac failure); seen in polished-rice-consuming populations.

Riboflavin (B2) deficiency gives angular stomatitis, cheilosis, glossitis and nasolabial seborrhoea; niacin (B3) deficiency causes pellagra with the four Ds: dermatitis, diarrhoea, dementia, death.

Vitamin C (ascorbic acid): deficiency causes scurvy - bleeding gums, petechiae, poor wound healing, anaemia; destroyed by prolonged cooking and high heat.

Vitamin B12 deficiency causes megaloblastic anaemia and neurological damage; intrinsic factor from the stomach is needed for absorption; vegans are at risk.

Iron: richest in liver, meat, egg yolk, green leafy vegetables; haem iron is absorbed better than non-haem; absorption is enhanced by vitamin C and inhibited by phytates and tannins. Deficiency causes microcytic hypochromic anaemia.

Iodine deficiency causes goitre, cretinism and mental impairment; iodised salt is the main preventive measure. Calcium and phosphorus deficiency leads to poor bone mineralisation; zinc deficiency causes growth retardation and delayed wound healing.

Energy units: 1 kilocalorie (kcal) = 4.184 kilojoules (kJ); 1 MJ = 239 kcal. Atwater factors: carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g.

Basal metabolic rate (BMR) is energy for involuntary functions at complete rest, 12-14 hours after a meal, in a thermoneutral environment; it accounts for roughly 60-70% of total daily energy expenditure.

BMR is raised by fever, hyperthyroidism, pregnancy, growth and lean body mass; it is lowered by ageing, starvation and hypothyroidism.

Harris-Benedict and ICMR equations estimate BMR; total energy expenditure = BMR x physical activity factor plus diet-induced thermogenesis (about 10% of intake).

Physical activity levels: sedentary 1.4, moderately active 1.6, heavy 1.9 (ICMR factors); a heavy worker therefore needs roughly 35-40% more energy than a sedentary worker of the same age.

ICMR recommended daily allowances for an adult man (sedentary) are about 2,320 kcal and for an adult woman (sedentary) about 1,900 kcal, adjusted for activity, pregnancy and lactation.

Energy balance: intake greater than expenditure leads to weight gain and obesity; intake less than expenditure leads to weight loss and, if prolonged, to wasting.

1 kg of body fat corresponds to roughly 7,700 kcal; a daily deficit of about 500 kcal produces about 0.5 kg loss per week.

Diet-induced thermogenesis (thermic effect of food) is highest for protein (20-30%), lower for carbohydrate (5-10%) and fat (2-3%).

Digestion begins in the mouth: salivary alpha-amylase (ptyalin) hydrolyses starch to maltose at pH 6.8-7.0; no protein or fat digestion occurs in the mouth.

Stomach: hydrochloric acid denatures protein and activates pepsinogen to pepsin; gastric lipase starts fat digestion; rennin curdles milk in infants; intrinsic factor is secreted for vitamin B12 absorption.

Small intestine is the main site of digestion and absorption; pancreatic amylase, trypsin, chymotrypsin, lipase and intestinal brush-border enzymes complete hydrolysis.

Bile salts from the liver and gall bladder emulsify fat into micelles; fat absorption occurs mainly in the jejunum and requires bile salts and pancreatic lipase.

Absorption: monosaccharides and amino acids pass into portal blood by active transport or facilitated diffusion; long-chain fatty acids are re-esterified into chylomicrons and enter lymph (lacteals).

Water-soluble vitamins are absorbed into portal blood; fat-soluble vitamins A, D, E and K are absorbed with micelles and depend on bile.

Large intestine absorbs water and electrolytes and hosts colonic bacteria that ferment fibre; it has no significant role in absorbing macronutrients.

Metabolism: glycolysis breaks glucose to pyruvate (net 2 ATP); the citric acid cycle and oxidative phosphorylation in mitochondria yield most ATP; the pentose phosphate pathway supplies NADPH and ribose.

Gluconeogenesis makes glucose from lactate, glycerol and amino acids; lipogenesis converts excess carbohydrate to fat; deamination of amino acids removes the nitrogen as urea.

A balanced diet supplies energy and all essential nutrients in correct proportion, with adequate fibre and water, and is palatable, affordable and culturally acceptable.

ICMR dietary guidelines: eat a variety of foods; ensure cereals and millets, pulses, milk, vegetables and fruits daily; limit fat, sugar and salt; use iodised salt; maintain adequate physical activity.

The food exchange list groups foods of similar energy and macronutrient content so that one item can replace another in measured portions without changing the nutrient value of the diet.

Typical Indian exchange groups: cereal/starch, pulse/dal, milk, meat/fish/egg, vegetables (A and B), fruit, fat/oil, and sugar - each exchange supplies a defined energy value, roughly 80-90 kcal for cereal and pulse exchanges.

Meal planning steps: assess needs (age, sex, activity, physiological state), fix total energy, distribute energy among meals (breakfast 25%, lunch 30-35%, dinner 25-30%, snacks 10%), then choose foods from each group.

A 2,000 kcal vegetarian day might use about 10 cereal exchanges, 3 pulse exchanges, 3 milk exchanges, 4 vegetable exchanges, 2 fruit exchanges and 4 fat exchanges, adjusted to the individual.

Meal frequency and timing matter: 3 main meals plus 2 snacks is preferred; skipping breakfast and large late-night meals are associated with poorer dietary quality.

Food labels and standard measures help portion control; one katori (cup) of cooked rice is roughly 30 g raw rice; one idli is roughly 25-30 g of cereal exchange.

Infancy (0-6 months): exclusive breastfeeding gives about 100-120 kcal/kg/day; colostrum supplies immunoglobulin A and is high in protein, zinc and vitamin A.

Complementary feeding starts at 6 months while breastfeeding continues to 2 years; the first foods are mashed cereal-pulse mixtures, then fruits, vegetables, egg and fish for iron and zinc.

Childhood (1-3 and 4-6 years): energy needs are about 1,060-1,360 kcal/day; small frequent meals and nutrient-dense foods are needed because gastric capacity is small.

Adolescence: the growth spurt raises protein, calcium, iron and zinc needs; girls need extra iron after menarche; peer influence and fast food increase risk of obesity and anaemia.

Pregnancy: extra energy about 350 kcal/day in the second and third trimesters, extra protein about 15-20 g/day, plus iron and folate supplementation to prevent anaemia and neural tube defects.

Lactation: extra energy about 500-600 kcal/day and extra protein about 15-20 g/day; milk output is about 750 ml/day, so fluid intake and calcium must be adequate.

Old age: energy need falls with lower BMR and activity, but protein, calcium and vitamin D needs stay high; low-sodium, high-fibre, soft-textured diets help prevent constipation, osteoporosis and hypertension.

Physiological states with high nutrient density demands: pregnancy, lactation, infancy, adolescence and convalescence - meals must be small in volume but rich in protein, vitamins and minerals.

Food-borne illness causes: bacteria (Salmonella, Staphylococcus aureus, Clostridium botulinum, Escherichia coli, Vibrio cholerae), viruses (hepatitis A, norovirus), parasites (Entamoeba, Taenia) and toxins (aflatoxin from Aspergillus flavus in groundnuts and cereals).

Key hygiene rules: wash hands before handling food, use clean water, separate raw and cooked food, cook thoroughly, keep food at safe temperatures, and protect food from flies and rodents.

Danger zone for bacterial growth is 5-60 degrees Celsius; cooked food should be kept hot above 60 degrees Celsius or chilled below 5 degrees Celsius and not left out for more than 2 hours.

Food preservation methods: drying and dehydration, salting, sugaring, pickling in acid, refrigeration and freezing, canning and bottling, pasteurisation, irradiation and addition of chemical preservatives.

Drying and salting work by lowering water activity so that microorganisms cannot multiply; fermentation (curd, idli batter, pickle) produces acid that inhibits spoilage organisms.

Refrigeration slows but does not kill microorganisms; freezer storage at -18 degrees Celsius stops microbial growth but does not destroy enzymes, so blanching is used before freezing vegetables.

Aflatoxin is a heat-stable mycotoxin linked to liver cancer; prevention means drying grains properly, storing them dry and cool, and discarding mouldy groundnuts and cereals.

Personal hygiene, safe water supply, clean utensils, proper garbage disposal and pest control are the five pillars of food safety in the home and in food service establishments.

Malnutrition includes undernutrition (underweight, stunting, wasting, micronutrient deficiency) and overnutrition (overweight, obesity, diet-related non-communicable disease); India faces the double burden of both.

WHO classification uses weight-for-age, height-for-age and weight-for-height z-scores; stunting is low height-for-age (chronic), wasting is low weight-for-height (acute).

Major deficiency disorders in India: protein-energy malnutrition, iron-deficiency anaemia, vitamin A deficiency, iodine deficiency disorders, and vitamin D and calcium deficiency.

National programmes: Integrated Child Development Services (ICDS) for children under 6, pregnant and lactating women; Mid-Day Meal (now PM POSHAN) for school children; Poshan Abhiyaan for nutrition outcomes.

Anaemia Mukt Bharat targets anaemia through iron-folic acid supplementation, deworming, fortified foods and behaviour change; iodised salt is promoted under the National Iodine Deficiency Disorders Control Programme.

Food fortification adds micronutrients to staples: iodised salt, iron-fortified wheat flour, vitamin A-fortified oil and double-fortified salt; biofortification develops nutrient-rich crop varieties.

Community assessment uses anthropometry, dietary surveys, clinical signs and vital statistics; growth monitoring charts and MUAC are used to screen children at anganwadi level.

Nutrition education and dietary diversification, along with food security and sanitation, are the sustainable long-term interventions; supplementation is a short-term measure for high-risk groups.