A. FUNDAMENTALS OF FOOD AND NUTRITION
1. Food
Food comprises substances consumed to provide energy, nutrients, water, and other components required for growth, maintenance, physiological functions, and health. Food may also contribute to sensory, cultural, and social needs.
2. Nutrition
Nutrition is the science of the ingestion, digestion, absorption, metabolism, utilization, and excretion of nutrients and other food components and their effects on health and physiological function.
3. Nutrients
Nutrients are chemical substances required by the body for energy production, growth, tissue maintenance, regulation of physiological processes, and normal development. Major nutrient groups include carbohydrates, proteins, fats, vitamins, minerals, and water.
4. Animal and Plant Proteins
Proteins obtained from foods of animal origin are commonly described as animal-source proteins, while those obtained from plant foods are plant-source proteins. Protein quality depends on amino-acid composition, digestibility, bioavailability, and processing.
5. Energy from Protein
Protein provides approximately 4 kcal (17 kJ) per gram of metabolizable dietary energy under conventional food-energy calculations. Actual physiological energy yield can vary with protein digestibility and metabolism.
6. Protein Requirements
Protein requirements are not identical for every adult. They vary with age, body size, physiological state, physical activity, health status, and dietary pattern. A commonly used adult reference intake is approximately 0.8 g protein/kg body weight/day, but this is not a universal requirement for every individual.
7. Energy from Carbohydrates
Available carbohydrate provides approximately 4 kcal (17 kJ) per gram. The amount of carbohydrate required varies according to total energy needs and dietary pattern rather than being a fixed daily mass for all adults. WHO recommends that carbohydrate intake should primarily come from whole grains, vegetables, fruits, and pulses.
8. Energy from Fat
Dietary fat provides approximately 9 kcal (37 kJ) per gram, making it the most energy-dense macronutrient. Fat also supplies essential fatty acids and facilitates absorption of fat-soluble vitamins.
9. Dietary Fat and Health
The health effect of dietary fat depends on its type, amount, food source, and overall dietary pattern. Replacing saturated and trans fats with unsaturated fats is generally preferred for cardiovascular health. WHO recommends limiting saturated fat and avoiding industrially produced trans fat.
10. Calcium and Phosphorus
Calcium and phosphorus are essential minerals involved in bone and tooth structure, cellular functions, energy metabolism, and other physiological processes. Approximately 85% of body phosphorus is associated with bones and teeth, although distribution varies with physiological state.
B. MINERALS AND VITAMINS
11. Minerals
Minerals are inorganic elements required for physiological functions. They do not provide dietary energy and are not destroyed simply by heating, although food processing can cause mineral losses through leaching, separation, refining, or other physical processes.
12. Major and Trace Minerals
Minerals are commonly classified according to the amounts required by the body as major minerals and trace elements. Calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur are generally considered major minerals, while iron, zinc, iodine, selenium, copper, manganese, and others are required in smaller amounts.
13. Dietary Sources of Calcium
Important calcium sources include milk and dairy products, calcium-set tofu, certain fish eaten with bones, fortified foods, and some leafy vegetables and other plant foods. Butter and ghee are not major calcium sources because they contain little of the milk’s aqueous mineral fraction.
14. Micronutrients
Vitamins and minerals are collectively called micronutrients because they are required in relatively small quantities but perform essential biological functions. Deficiency of micronutrients can produce serious health consequences.
15. Vitamins
Vitamins are organic compounds required in small amounts for normal physiological functions. Most must be obtained from the diet, although the body can synthesize or convert certain vitamin compounds under appropriate conditions.
16. Fat-Soluble Vitamins
The fat-soluble vitamins are A, D, E, and K. They are absorbed with dietary fat and can be stored in the body to a greater extent than most water-soluble vitamins.
17. Water-Soluble Vitamins
The major water-soluble vitamins are vitamin C and the B-complex vitamins. They generally have limited body storage compared with fat-soluble vitamins, although exceptions such as vitamin B12 exist.
18. B-Complex Vitamins
The eight recognized B vitamins are thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), vitamin B6, biotin (B7), folate (B9), and vitamin B12. They participate in energy metabolism, amino-acid metabolism, DNA synthesis, red-cell formation, and other biochemical processes.
19. Dietary Fibre
Dietary fibre consists primarily of non-digestible carbohydrate polymers and other substances defined by the relevant nutritional methodology. Important fibre components include cellulose, hemicelluloses, pectins, β-glucans, gums, resistant starch, and some oligosaccharides. Fibre has important effects on gastrointestinal function and metabolic health. WHO recommends that adults consume at least 25 g/day of naturally occurring dietary fibre.
20. Sources of Dietary Fibre
Major dietary sources include whole grains, pulses, vegetables, fruits, nuts, seeds, and other plant foods. The amount and type of fibre differ substantially among foods and processing methods.
C. NUTRITIONAL DEFICIENCIES
21. Nutritional Deficiency
A nutritional deficiency occurs when intake, absorption, utilization, or availability of a nutrient is insufficient to meet physiological requirements over time. Deficiency may result from inadequate dietary intake, malabsorption, increased requirements, disease, or other factors.
22. Protein-Energy Malnutrition
Protein-energy malnutrition (PEM) refers broadly to forms of undernutrition caused by inadequate energy and protein intake or availability. In modern clinical nutrition, conditions are more precisely described using terms such as wasting, stunting, underweight, and specific forms of acute or chronic malnutrition.
23. Childhood Undernutrition
Young children are particularly vulnerable to undernutrition because of their high nutrient requirements relative to body size and rapid growth. Inadequate food intake, infections, poor absorption, and socioeconomic and environmental factors can contribute to childhood malnutrition.
24. Kwashiorkor
Kwashiorkor is a form of severe acute malnutrition characterized by bilateral pitting oedema and other clinical and metabolic abnormalities. It should not be defined simply as protein deficiency with adequate calories because its pathophysiology is multifactorial.
25. Marasmus
Marasmus is a severe form of acute malnutrition characterized primarily by marked wasting resulting from prolonged inadequate energy and nutrient intake. It commonly presents with severe loss of body fat and muscle mass.
26. Vitamin A Deficiency
Vitamin A deficiency can cause xerophthalmia, including conjunctival and corneal abnormalities, and can impair immune function. Severe deficiency can lead to visual impairment and blindness.
27. Thiamin Deficiency
Severe deficiency of thiamin (vitamin B1) causes beriberi. Populations consuming highly polished rice as a major staple may be at increased risk when dietary thiamin intake is inadequate.
28. Vitamin C Deficiency
Severe vitamin C deficiency causes scurvy, which may produce fatigue, impaired wound healing, bleeding gums, and other manifestations related to defective collagen synthesis.
29. Iodine Deficiency
Iodine deficiency impairs thyroid-hormone synthesis and can cause goitre, hypothyroidism, impaired fetal and childhood development, and other iodine-deficiency disorders. The consequences are particularly important during pregnancy and early childhood.
30. Iodized Salt
Salt iodization is an important public-health strategy for preventing and controlling iodine deficiency. WHO recommends iodization of food-grade salt as an effective population-level intervention, while the actual iodine concentration and legal requirements are determined by the applicable national programme.
D. FOODS AS SOURCES OF NUTRIENTS
31. Cereals as Energy Sources
Cereals such as rice, wheat, maize, oats, sorghum, and millet are major sources of dietary carbohydrate and energy in many populations. Their nutritional contribution also includes protein, fibre, vitamins, minerals, and bioactive compounds.
32. Sprouting and Nutrient Changes
Germination or sprouting can alter the nutritional composition of cereals and legumes. Depending on the seed and conditions, it can increase the synthesis or availability of certain compounds, including vitamin C and some bioactive compounds, while reducing some antinutritional factors.
33. Meat, Fish and Poultry
Meat, fish, and poultry provide high-quality protein, essential amino acids, vitamin B12, iron, zinc, selenium, and other nutrients. Their nutritional composition varies according to species, cut, fat content, processing, and preparation.
34. Fruits as Vitamin C Sources
Fruits such as citrus fruits, guava, and Indian gooseberry (amla) can provide substantial amounts of vitamin C. Vitamin C content varies with species, cultivar, maturity, storage, and processing.
35. Nuts and Seeds
Nuts and seeds generally provide protein, unsaturated fatty acids, dietary fibre, minerals, and vitamin E. Their nutritional composition varies considerably among species.
E. BIOCHEMISTRY OF NUTRITION
36. Ribose
Ribose is a five-carbon monosaccharide that forms part of important biological molecules, including ATP, NAD, NADP, FAD, RNA, and several nucleotide-related compounds. Ribose is therefore important in cellular energy metabolism and genetic information systems.
37. Catabolism
Catabolism comprises metabolic pathways that break down complex molecules into smaller molecules, often releasing energy that can be captured in forms such as ATP or reducing equivalents.
38. Glycolysis
Glycolysis is a series of enzymatic reactions in which glucose or another glycolytic substrate is converted to pyruvate, with production of ATP and reduced NADH. It occurs in the cytosol and does not require oxygen directly.
39. Triglycerides
Triglycerides, also called triacylglycerols, consist of a glycerol backbone esterified with three fatty acids. They are the principal storage form of fat in many foods and in adipose tissue.
40. Cis Unsaturated Fatty Acids
Many naturally occurring unsaturated fatty acids contain cis double bonds, which introduce bends into the hydrocarbon chain and influence the physical properties of fats. However, not every naturally occurring unsaturated fatty acid is necessarily cis, so the statement should not be treated as universal.
41. Essential Fatty Acids
The two principal essential fatty acids for humans are linoleic acid (LA, omega-6) and alpha-linolenic acid (ALA, omega-3). They must be obtained from the diet because humans cannot synthesize their parent carbon-chain structures in sufficient amounts.
42. Amino Acids
Amino acids are organic compounds containing an amino group, carboxyl group, hydrogen atom, and variable side chain in the common structure of proteinogenic α-amino acids. The side chain determines many of their chemical and biological properties.
43. Enzymatic Reactions
In an enzyme-catalyzed reaction, the starting molecule acted upon by the enzyme is called the substrate, and the molecules formed during the reaction are called products. Enzymes accelerate reactions by lowering the activation-energy barrier.
F. LIPIDS, SWEETENERS AND FOOD PROPERTIES
44. Meat Fat and Cholesterol
Meat fat contains a mixture of saturated, monounsaturated, and polyunsaturated fatty acids, and the composition varies by animal species, tissue, diet, and processing. Meat cholesterol content also varies substantially, so a fixed value such as 75 mg/100 g should not be treated as a universal composition value.
45. Hydrogenation of Oils
Hydrogenation involves the addition of hydrogen to carbon-carbon double bonds in unsaturated fatty acids. Partial hydrogenation can produce more saturated fatty acids and may generate trans fatty acids, depending on the process. Modern food formulation generally seeks to minimize industrially produced trans fat.
46. Smoke Point
Smoke point is the approximate temperature at which a fat or oil begins to produce visible smoke under specified test conditions. It is influenced by the oil’s composition, free fatty acid content, impurities, refining, and heating conditions.
47. Sugar Alcohols
Mannitol and xylitol are sugar alcohols (polyols) used as food ingredients. Xylitol is widely used in products such as sugar-free chewing gum and confectionery, while mannitol is used in selected confectionery, pharmaceutical, and food applications. Their specific permitted uses depend on national regulations.
48. Alitame
Alitame is an intense high-potency sweetener derived from amino-acid components. Its sweetness is much greater than that of sucrose, but the exact sweetness ratio depends on the reference conditions and formulation. Regulatory approval and permitted uses differ among jurisdictions.
49. Aspartame
Aspartame is an intense sweetener composed of aspartic acid and phenylalanine in a methyl ester structure. Because it provides phenylalanine, products containing aspartame require appropriate labeling for individuals with phenylketonuria (PKU) where required by applicable regulations.
50. Saccharin
Saccharin is a high-intensity sweetener used in several forms, including saccharin and its permitted salts. It is substantially sweeter than sucrose, but the exact sweetness intensity varies with concentration, pH, food matrix, and comparison method. Its permitted uses and maximum levels are jurisdiction-specific.
NUTRITIONAL PRINCIPLE
A scientifically sound approach to foods and nutrition recognizes that no single food or nutrient determines health by itself. Nutritional adequacy depends on the overall dietary pattern, energy balance, nutrient density, food diversity, physiological needs, and individual circumstances. WHO describes a healthy diet in terms of adequacy, balance, moderation, and diversity, while emphasizing foods such as whole grains, vegetables, fruits, pulses, nuts, and other nutrient-dense foods.