Basic concepts

A diet history records what a person usually eats, including meal timing, food choices, portions, preparation methods, beverages, supplements, restrictions, and appetite. It helps identify nutrient gaps, excesses, allergies, and habits relevant to disease management. It is a dietary assessment tool, not a method for manufacturing medicine or designing a house. A is correct.

Nutrient density describes how many essential nutrients a food provides in relation to its energy, weight, or serving size. A nutrient-dense food supplies substantial vitamins, minerals, protein, fibre, or other beneficial nutrients without excessive calories. Vegetables, fruits, pulses, eggs, and milk can be nutrient-dense choices. Therefore, A is correct.

Empty-calorie foods provide substantial energy, usually from added sugars or solid fats, but contain little fibre, protein, vitamins, or minerals. Frequent intake of sugary drinks, sweets, and some fried snacks can displace nutritious foods and promote excess calorie consumption. They are not literally without calories; the term means low nutrient value relative to energy. A is correct.

Bioavailability is the proportion of an ingested nutrient that is absorbed and becomes available for physiological use or storage. It depends on the nutrient’s chemical form, food composition, digestion, health status, and interactions with other substances. For example, vitamin C can improve absorption of non-haem iron. Thus, B is correct.

Digestion is the mechanical and chemical breakdown of complex food substances into smaller molecules that can be absorbed and used by the body. Chewing, stomach movements, enzymes, and digestive juices all contribute to this process. Digestion prepares nutrients for absorption, but it is not the same as absorption itself. Therefore, A is correct.

Absorption is the movement of digested nutrients across the wall of the gastrointestinal tract into the blood or lymph. It occurs mainly in the small intestine, where villi and microvilli provide a large surface area. Once absorbed, nutrients are transported to cells for energy, growth, repair, and regulation. Therefore, B is correct.

Metabolism is the complete set of chemical reactions continuously taking place inside the body. These reactions break down nutrients to release energy and also use nutrients to build and repair cells, tissues, enzymes, and hormones. Therefore, option A is correct; the other options are household activities and have no connection with metabolism.

Protein is especially important during growth because it supplies amino acids needed to build and repair muscles, skin, blood, enzymes, hormones, and other body tissues. Children and adolescents require adequate protein as their bodies are growing rapidly. Salt, spices, and water colour cannot perform this tissue-building function, so option A is correct.

Vitamin A is needed for the formation of visual pigments that help the eyes function in dim light. Its deficiency may cause night blindness, in which a person has difficulty seeing after dusk or in darkness. Vitamin A also supports immunity and epithelial tissues, but the characteristic deficiency sign asked here is night blindness, making option A correct.

Vitamin D promotes the intestinal absorption and proper use of calcium and phosphorus. These minerals are essential for forming and maintaining strong bones and teeth. Vitamin K has the major role in blood clotting, iron and vitamin B12 are associated with red blood-cell formation, and vitamin E is an important antioxidant. Therefore, option A is correct.

Iron is an essential component of haemoglobin, the red pigment in red blood cells that carries oxygen from the lungs to body tissues. Adequate iron supports normal energy production and prevents iron-deficiency anaemia, which may cause tiredness and weakness. The other options are biologically meaningless, so option A is correct.

Calcium is the principal mineral that gives bones and teeth strength and structure. It also participates in muscle contraction, nerve transmission, and blood clotting, but its best-known nutritional role is skeletal health. Vitamin D helps the body absorb and use calcium effectively. Thus, the statement about bones and teeth in option A is correct.

Sodium is the major extracellular electrolyte and helps regulate the movement of water between body compartments. It also contributes to nerve impulses and muscle function. Excessive sodium intake can promote water retention and raise blood pressure in susceptible people, whereas abnormal losses can disturb fluid balance. Therefore, option A is the correct broad relationship.

Adequate nutrition supports the production and activity of immune cells, antibodies, and protective barriers. Protein is needed for immune tissues, while vitamins and minerals such as A, C, D, E, zinc, and iron support different defence processes. Good nutrition does not guarantee that illness will never occur, but it helps maintain resistance and recovery; hence option A is correct.

Diet therapy means planning or modifying food intake so that it supports medical treatment and meets the patient's nutritional needs during disease. Depending on the condition, changes may involve energy, protein, salt, fat, fibre, fluids, or food texture. It does not replace all medical care or remove all foods. Therefore, option A is correct.

Average nutrient requirements may differ because body size, lean mass, energy expenditure, and physiological conditions are not identical for everyone. In addition, pregnancy and lactation create increased needs for energy, protein, iron, folate, iodine, and other nutrients. These are biological and life-stage considerations, not rigid rules for every individual. Hence option A gives the valid reason.

Physical activity increases energy expenditure because working muscles require ATP, which is produced from nutrients. Therefore, a person who exercises heavily or performs physically demanding work generally needs more energy than a sedentary person, although the exact amount depends on body size, age, sex, and activity intensity. Activity does not eliminate energy needs; it changes them. Thus, option A is correct.

Different foods contain different combinations and amounts of nutrients. Cereals may provide energy, pulses and milk provide protein, fruits and vegetables supply vitamins, minerals, fibre, and protective compounds, and nuts or oils provide fats. No single ordinary food supplies every nutrient in adequate amounts. Eating varied foods therefore improves dietary adequacy and balance, making option A correct.

A dietitian assesses a person's health, dietary intake, nutritional risks, medical condition, and goals. On that basis, the dietitian plans an appropriate diet, explains practical changes, monitors progress, and provides counselling or education. Dietitians may work with healthy people as well as patients, but building houses, manufacturing medicines, or merely selling food are not their basic professional roles. Hence option A is correct.

Basic nutrition concepts explain nutrients, their functions, food sources, requirements, deficiency effects, and the meaning of a balanced diet. This knowledge helps people make sensible choices for health and enables students or professionals to understand therapeutic diets used in disease. It does not merely concern appearance or photography. Therefore, option A correctly states its importance.

Essential amino acids are amino acids that the human body cannot synthesise in sufficient quantities to meet its needs. They must therefore be supplied through food, especially good-quality protein sources; requirements can vary with age and physiological condition. They are not found only in water or spices, and amino acids can contribute to energy when necessary. Thus, option A is correct.

Water-soluble vitamins, especially the B-complex vitamins and vitamin C, are not stored in the body in large reserves for long periods. Excess amounts are generally excreted in urine, so a person needs a regular dietary supply. If intake remains inadequate, body stores can fall and deficiency symptoms may appear comparatively quickly.

Minerals are essential inorganic nutrients with structural, regulatory and protective roles. Calcium and phosphorus help form bones and teeth, iron is needed for haemoglobin, and sodium and potassium help maintain fluid balance and nerve or muscle activity. Therefore, their functions are much broader than appearance or taste.

Nutrient requirement means the amount needed by a person to maintain health, growth and normal body functions, whereas dietary intake means the nutrients actually consumed through food and beverages. Comparing the two helps identify adequacy, deficiency, excess or imbalance and supports sound nutrition assessment and diet planning.

A complete protein supplies all the essential amino acids that the body cannot synthesise in adequate amounts, and it provides them in a suitable proportion for tissue building and repair. Many animal foods, such as eggs and milk, are high-quality sources, although a well-planned plant diet can also achieve adequacy through complementation.