Nutrition and dietetics
Nutrition and dietetics is the science of food and how it affects human health. It is a wide field that includes the study of nutrients, food, and the body’s metabolism.
Nutrition and dietetics include the following:
- Basics of Nutrition
- Food groups and their nutrition value
- Cooking methods and their effects on nutrients
- Nutritional requirements for different age groups
- Malnutrition and its prevention
- Diet therapy for various diseases
- Food Safety and hygiene
In addition, for Tnpsc it is good to have an understanding of the following:
- Government policies and schemes on nutrition and dietetics
- Role of nutritionist or dietetic in society
- Latest news in the field of nutrition and dietetics
Basics of Nutrition
The seven elements of nutrition are:
The life of all living organisms is due to several types of nutrition processes. The process of nutrition involves ingestion, digestion, absorption and assimilation of food. The composition of nutrients differs in different types of feeding. But for every living organism, the nutrient consists of organic and inorganic components.
The components of nutrients are carbohydrates, proteins, lipids, vitamins, minerals and water. Each of these nutrient components has a specific function. A good nutrient intake depends on several factors such as the stage of growth, sex, health condition, body activities and environment.
Classification of Nutrition
Carbohydrates that is Poly Hydroxyaldehydes or Ketones are composed of Carbon, Hydrogen, and Oxygen in the ratio of 1:2:1 (CH2 O)n. Carbohydrates are of three types, they are monosaccharides, disaccharides and Polysaccharides.
Monosaccharides are the simplest form of carbohydrates composed of a single organic molecule. Based on the number of carbon atoms, Monosaccharides are classified into trioses, tetroses, pentoses and hexoses.
The trioses that are C3H6O3 are common intermediary products in carbohydrate metabolic processes and play a vital role in the interconversion of biomolecules. An example is Glyceraldehydes.
Pentoses that are C5H10O5 like ribose and deoxyribose are an important part of RNA and DNA molecules. The Hexoses (C6 H12 O6) such as glucose, fructose and galactose are commonly consumed food components.
Carbohydrates provide energy for the cells. The energy metabolism happens through the glycolytic process that involves an oxidative, citric acid cycle. The liberated energy is stored in ATP(Adenosine triphosphate) form.
Every gram of carbohydrate could give energy equivalent to 4.1 calories.
Disaccharides are the carbohydrates formed by the condensation of two monosaccharide monomers. Found in Milk and Sugar. Common Disaccharides are Maltose, Sucrose and Lactose.
Disaccharides have the following composition:
Maltose (In germinating cereals) – Glucose + Glucose
Sucrose (Cane Sugar) – Glucose + Fructose
Lactose (Milk) – Glucose + Galactose
Polysaccharides are complex carbohydrates formed by the polymerisation of a large number of monosaccharides. In nature, there are a lot of Polysaccharides. Several polysaccharides are structural components in nature such as Chitin, and Cellulose.
Starch molecules serve as storage of food materials trapping huge quantities of energy. It is available as pectin and amylopectin molecules in food grains. A polysaccharide found in muscles and the liver as Glycogen.
Protein (Polypeptides) are nitrogen compounds made of carbon, hydrogen, oxygen and nitrogen. It also contains Sulphur. Protein plays an important role in the structural organisation of living beings.
Example: Cells Membrane, nails, muscles, hair. Many proteins serve as Enzymes and are named functional proteins. Amino Acids are the building block of proteins. Types of Amino Acids are Glycine, alanine, serine, valine, leucine, proline etc.
The amino acids are classified into essential and non-essential amino acids. Our body cannot synthesise or produce essential amino acids. The essential amino acids must be taken through food. The essential amino acids are Arginine, valine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine and tryptophan.
Non-essential amino acids can be produced in our bodies using other compounds. A protein or a polypeptide chain is made of several amino acids linked with peptide bonds. This linear arrangement is termed the primary organisation of proteins.
The amino acid sequence and organisation are determined genetically. Therefore the genome plays an important role due to the capability to produce some type of proteins for bringing genetic characteristics.
The daily intake of protein as ICMR and WHO is 1gm per kg body weight. Protein deficiency is Kwashiorkor, Marasmus etc.
Vitamins are complex organic compounds, whose presence in very small amounts in food is essential for physiological activities and essential growth. Vitamins do not have any energy value.
However, Vitamins are essential for controlling energy-yielding processes. Vitamins are classified as A, B, C, D, E and K. Out of these Vitamins, B and C are water-soluble.
Vegetables or Fruits containing Vitamin B and C when washed in water after cutting may lose all the vitamins contained in them. Some vitamins such as A, D, E and K when consumed more than required may cause defects called Vitaminosis.
We use Vitamin-D or Calciferol when our body is exposed to Sunlight, produced by our body by a lipid compound called Ergosterol, which is found below the skin.
Hence Vitamin-D is called Sunshine Vitamin.
Important Functions of Vitamins
- Physiological Processes
- Vitamin A has an important role in Visual perception.
- Vitamin E for fertility in animals.
- Vitamin K for Blood clotting in animals.
- Vitamin C for immunity against infections and also supports processes of growth.
- Maintenance of Body Tissue
- The epithelial tissues in animals are maintained by vitamin A and B2.
- Vitamin D is for the growth of bones.
- Vitamin E for rejuvenation of tissues.
- Vitamin B1 for nourishment to nerve cells.
- Vitamin B12 for the maturation of erythrocytes.
- Metabolic Processes
- The process of calcium and phosphorus metabolism work in the presence of vitamin D.
- Vitamin E remains an antioxidant.
- Vitamin B1 remains a coenzyme in tissue metabolism and is useful in the oxidation of glucose in the CNS.
- Vitamin B2 is essential for carbohydrate metabolism.
- Vitamin B which is Niacin has an important role as a coenzyme and is essential for oxidation and reduction reactions.
- Normal metabolism of amino acids and fat is because of Vitamin B6.
- Vitamin B which is Biotin serves as a coenzyme and cofactor in oxidative metabolism.
- Vitamin C activates certain intra-cellular enzymes.
Vitamin Deficiency Ailments
Vitamin A Deficiency Ailments
- Atrophy of lacrimal glands of the eye and reduction in tear secretion.
- Corneal epithelium becomes red and dries called Xerosis.
- Corneal epithelium becomes wrinkled and Keratinised called Xerophthalmia.
- The appearance of Bitot’s spot in the cornea might occur.
- Cornea gets necrosed and infected called Keratomalacia.
- Can cause night blindness called Nyctalopia.
Vitamin D Deficiency Ailments
- Affects the calcification of bones.
- Vitamin D deficiency causes rickets in growing children.
- Osteomalacia in adults.
Vitamin E Deficiency Ailments
- Rare in Humans, cause sterility issues in experimental animals.
Vitamin K Deficiency Ailments
- Vitamin-K deficiency can lead to a defect in blood coagulation.
- In humans, Vitamin-K deficiency can lead to hemorrhagic manifestation.
Vitamin B1 Deficiency Ailments
- Vitamin B1 deficiency can lead to a condition known as BeriBeri that affects the nervous and cardiovascular systems.
Vitamin B2 Deficiency Ailments
- Loss of appetite.
- Other gastrointestinal symptoms, soreness and burning of lips, mouth and tongue.
- Fissures appear at the edges of the mouth.
Vitamin Niacin Deficiency Ailments
- Vitamin Niacin deficiency leads to pellagra.
- Pellagra symptoms are mental changes, dementia or dermatitis and stomatitis.
- The tongue becomes smooth, red and painful.
Vitamin B6 Deficiency Ailments
- In humans, pyridoxine deficiency causes dermatitis around the eyes, nose and behind the ears.
- Fissures appear above the lips and angles of the mouth.
Vitamin B12 Deficiency Ailments
- Its deficiency causes pernicious anaemia, that is sore tongue and many neurological problems related to the spinal cord.
Vitamin C Deficiency Ailments
- Vitamin C Deficiency leads to Scurvy.
- Its symptoms are bleeding gums, loosening and falling of teeth.
- Intramuscular haemorrhages.
- Certain elements in small concentrations are necessary for some functions of the body.
- They are Sodium, Calcium, Potassium, Magnesium, Phosphorus, Sulphur and Chlorine, these must be present with great concentration.
- The minerals that are needed in small concentrations are iron, copper, zinc, cobalt, manganese, iodine and fluorine.
- Calcium, Magnesium and Phosphorus are needed in large concentrations for bodybuilding activities such as the formation of bones and teeth.
- Trace elements such as Manganese, copper, and zinc are needed for physiological activities such as oxygen transport (Iron), Iodine Hormone synthesis and manganese, copper, and zinc for intermediary metabolism.
- Chlorine, Sodium and Potassium form constituents of body fluids.
- Magnesium, sodium and potassium for neuromuscular irritability.
- Calcium for blood clotting.
- Calcium and potassium for cardiac function.
- The proportion of water in lean body mass (body fat content) is constant at around 71 to 78% in animals and humans.
- The total body water concentration varies with sex, age, and body weight.
- For a newborn child, water content is around 85 to 90%.
- For adults, the water content is 55 to 60%.
- ⅔ body water is found as intracellular fluid (ICF).
- ⅓ body water found as extracellular fluid (ECF)
- 25% of ECF is found in the plasma of blood.
- The average water intake is around 2500ml per day and exits from the body as water 1400ml.
- Water loss happens through Urine (1400ml), expiration (400ml), through the skin(600ml) and loss in faeces of about 100ml.
The function of water in the body
- Essential constituents of cells.
- Transport medium for nutrients and excretory products.
- Serves as a site for chemical reactions.
- Solvent for electrolytes, enzymes, hormones and vitamins.
- Maintenance of body temperature.
- Maintain the form and texture of tissues.
Nutrition and dietetics is the field of science which deals with food and how it affects the health of humans. It studies nutrients, food and the body’s metabolism.