Published by: Nuru
Published date: 10 Jan 2022
Nutrition is a process by which an organism obtains substances required for its proper growth, maintenance and to provide energy for all the activates. Nutrition includes food intake, absorption, assimilation, biosynthesis, energy metabolism, catabolism and excretion.
Nutrition is also known as food science, which relates to the nutrients essential for proper physical growth. Nutritious food is necessary to get energy and for physical growth, the formation of cells and tissues, movements of organs and protection of the body against diseases. We should take the balanced diet with all different groups of food.
Food or nutrient:
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as fats, proteins, vitamins, or minerals. The substance is ingested by an organism and assimilated by the organism's cells to provide energy, maintain life, or stimulate growth.
Functions of food:
Food provides our bodies with what they need to;
Food of human consists of;
1.Carbohydrates:
Carbohydrates are one of the main types of nutrients. They are the most important source of energy for your body. Your digestive system changes carbohydrates into glucose (blood sugar). Your body uses this sugar for energy for your cells, tissues and organs.
Daily requirement of carbohydrates;
Normal - 2400kcl/day
Pregnant - 2400+300kcl/day
Lactating - 2400+500kcl/day
Infants - 90+110kcl/day
Function of carbohydrates are:
Protein:
Proteins are large molecules consisting of amino acids which our bodies and the cells in our bodies need to function properly. Our body structures, functions, the regulation of the body's cells, tissues and organs cannot exist without proteins. The human body's muscles, skin, bones and many other parts contain significant amounts of protein. In fact, protein accounts for 20% of total body weight. Protein is broken down in to amino acids.
Amino acids:
Amino acids are biologically important organic compounds composed of amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, though other elements are found in the side-chains of certain amino acids. About 500 amino acids are known and can be classified in many ways
Characteristics of amino acid:
1.These are the basic unit of protein.
2.These are colorless, crystalline solids.
3.These are soluble in water and insoluble in organic solvents such as alcohol, acetone, etc.
4.There are 20 types of amino acid in nature.
5.The simplest amino acid is glycine.
Categories of amino acids:
They are divided in to two classes.
1.Essential amino acids:
Essential amino acids cannot be made by the body. As a result, they must come from food.The nine essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
2.Nonessential amino acids:
"Nonessential" means that our bodies produce an amino acid, even if we don't get it from the food we eat.They include: alanine, asparagine, aspartic acid, and glutamic acid.
Sources of protein:
The principle sources of proteins are both from plants and animals. In general the animal proteins are superior to plants proteins. There are two groups;
a.First class protein: The protein containing all the types of amino acids. They are animal protein like egg, meat.
b.Second class proteins: The protein do not containing all the types of amino acids. They are plant protein.
3. Lipids or fats:
Lipids are a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others. The main biological functions of lipids include storing energy, signaling, and acting as structural components of cell membranes. Lipids have applications in the cosmetic and food industries as well as in nanotechnology.
Sources of fat:
Cooking oil, butter, ghee, oil seeds, milk, meat, cheese, eggs, etc.
Classification of lipids:
1. Simple Lipids:
On hydrolysis gives fatty acids and alcohol (trihydric or monohydric).
Oils: Unsaturated fatty acid + glycerol.
Fats: Saturated fatty acids + glycerol,
Waxes: Fatty acids + mono or dihydric alcohol.
Simple glyceride: Contains same fatty acids. .
Mixed glyceride: Contains different fatty acids.
2. Compound lipids: (Complex lipids):
On hydrolysis gives phosphoric acid, various sugars, sphingosine, ethanolamine and serine in addition to fatty acids and glycerol.
a.Phospholipid: Fatty acids + glycerol + phosphoric acid + nitrogenous base.
e.g. Lecithin :Fatty acids + glycerol + phosphoric acid + choline
Cephalin: Fatty acids + glycerol + phosphoric acid + ethanolamine.
b. Glycolipids: Glycerol + fatty acid + Carbohydrates (on hydrolysis).
They are sub classified as galactosyl diglyceride, cerebrosides and sulpholipids.
c) Sphingophosphoiplds: Fatty acids + sphingosine + phosphoric acid + choline.
3) Derived Lipids:
Hydrolytic products of simple and compound lipids
i) Alcohols: Glycerol and other sterol
ii) Fatty acids
iii) Terpenoids
Functions of lipids:
1.Lipid provide energy fuel.
2.lipid act as thermal insulator.
3.Tryglycerides stored in adipose tissue as principle food reserve.
4.Lipids serve as solvents for fat soluble vitamins like A,D, E , and K.
5.They absorb mechanical impact around organs like eyeball preventing external shock.
6.Lipoprotein can prevent bacterial disease.
4.Vitamins:
A vitamin is an organic compound and a vital nutrient that an organism requires in limited amounts. An organic chemical compound is called a vitamin.
Fat soluble vitamins:
The fat-soluble vitamins, A, D, E, and K, are stored in the body for long periods of time and generally pose a greater risk for toxicity when consumed in excess than water-soluble vitamins. Eating a normal, well-balanced diet will not lead to toxicity in otherwise healthy individuals. However, taking vitamin supplements that contain megadoses of vitamins A, D, E and K may lead to toxicity. The body only needs small amounts of any vitamin.
Vitamin A (Retinol):
Vitamin A, also called retinol, has many functions in the body. In addition to helping the eyes adjust to light changes, vitamin A plays an important role in bone growth, tooth development, reproduction, cell division, gene expression, and regulation of the immune system.
Sources: Fish, liver oil, egg yolk, butter, cheese, milk, yellow and dark green leafy vegetable, papaya, tomatoes , carrots, guava, mango, etc.
Deficiency: Night blindness, Xerophthalmia, Reaterded growth, loss of glandular secretion, etc.
Vitamin D:
Vitamin D plays a critical role in the body’s use of calcium and phosphorous. It works by increasing the amount of calcium absorbed from the small intestine, helping to form and maintain bones. Vitamin D benefits the body by playing a role in immunity and controlling cell growth. Children especially need adequate amounts of vitamin D to develop strong bones and healthy teeth.
Sources: Vitamin D is found in oily fish (e.g., herring, salmon and sardines) as well as in cod liver oil. In addition to the vitamin D provided by food, we obtain vitamin D through our skin which produces vitamin D in response to sunlight.
Difeciency: Rickets or rachitis, Osteomalacea, teeth tetany.
Vitamin E:
It is also known as beauty vitamin because it maintains germinal epithelium of gonads for proper reproductive function. Vitamin E benefits the body by acting as an antioxidant, red blood cells, and essential fatty acids from destruction.
Sources: About 60 percent of vitamin E in the diet comes from vegetable oil (soybean, corn, cottonseed, and safflower). Vitamin E sources also include fruits and vegetables, grains, nuts (almonds and hazelnuts), seeds (sunflower) and fortified cereals.
Deficiency: Reversible sterility in females, Sperm sterility in males, Macrocytic anaemina, muscular dystrophy.
Vitamin K:
Vitamin K is naturally produced by the bacteria in the intestines, and plays an essential role in normal blood clotting, promoting bone health, and helping to produce proteins for blood, bones, and kidneys.
Sources: Good food sources of vitamin K are green, leafy-vegetables such as turnip greens, spinach, cauliflower, cabbage and broccoli, and certain vegetables oils including soybean oil, cottonseed oil, canola oil and olive oil. Animal foods, in general, contain limited amounts of vitamin K.
Deficiency: Causes blood clotting, Hypoprothrombinaemia, Haemorrhage,
Water-Soluble Vitamins:
These types of vitamins require regular supply in the form of dietary sources or supplements. These are nontoxic and easily absorbed into the body through the gastrointestinal tract and then disseminated in the tissues. Water-soluble vitamins are easily dissolved in water, it would be advisable not to overcook them and use the left over cooking water as healthy options in soups and sauces.
Balanced diet:
Balanced diet is the content of sufficient amount of all nutrients (carbohydrates, protein, vitamin, minerals, fats and water) required for keeping our body healthy and active. The proportion of the nutrients should be appropriate according to the daily needs. Unless there is a balance in our diet, we suffer from malnutrition.
In conclusion, the daily foods must contain the appropriate proportion of food from following three groups: -
Group A: Heat and energy giving foods like rice, corn, wheat, barley, millet, buckwheat, potato, honey, oil, ghee, etc.
Group B: Food for bodybuilding like fish, meat, pulse, beans, groundnuts, etc.
Group C: Foods for body-protection like green-leafy vegetables, sweet and sour fruits.
Importance of balanced diet