Human nutrition

Human nutrition

Human nutrition is the provision to obtain the essential nutrients necessary to support life and health.

Different types of food substances and their functions in human body

Proteins

These are substances which contain elements oxygen and nitrogen.

Source of proteins

Foods such as meat, liver, eggs, beans, milk, cheese, peas, groundnuts and mushrooms are good sources of protein.

Function of proteins

The following are the function of protein

1. It is used in body building.
2. Used by body for tissue growth and repair such as healing of wounds and replacement of skin.
3. Used as a source of energy, especially when the body lacks carbohydrates and lipids.
4. It enables red blood cells to transport oxygen in our bodies.

protein food

Carbohydrates

Carbohydrates are mainly made of carbon, hydrogen and oxygen.

Sources of carbohydrates

Foods such as maize, rice, bananas, potatoes, cassava, wheat (bread, cake) and yams are rich in carbohydrates.

Functions of carbohydrates

The following are the function of carbohydrates

1. They are chief source of energy.
2. In plants they are stored as starch.
3. In animals they are stored as glycogen.

carbohydrate foods

Lipids

These are compounds of carbon, hydrogen and oxygen. They are insoluble in water. Lipids are made up of fatty acid and glycerol.

Sources of lipids

Foods such as fish, nuts, seed oils, avocados and olives are good sources of lipids.

Functions of lipids

1. Lipids are used as a source of energy.
2. Protect the organs such as heart and kidneys.

Vitamins

Vitamins are chemical substances in small amounts that are used to maintain the body.

Vitamins can be grouped into two categories:

1. Water-soluble
2. Fat-soluble vitamins.

Fat-Soluble Vitamins can be stored in the body. Examples of fat-soluble vitamins are Vitamins A, D, E and K.

Water-Soluble Vitamins are not stored in the body. Vitamins B and C are water soluble. Vitamin B is of various forms, namely Vitamin B1, B2, B6 and B12.

Sources, functions and signs of vitamin deficiencies

Vitamins	Source	Function	Signs of deficiency
Vitamin A (retinol)	Liver, milk, carrots, orange, and yellow vegetable	Essential for the formation of membrane of the eyes and the respiratory tract	Night blindness, increased risk of infection
Vitamin B1 (thiamine)	Lean meat, liver, eggs, yeast extract and brown rice	Carbohydrate metabolism, coordination of muscle	Beriberi, a disease characterized by loss of appetite, muscle cramps disorder and heart failure
Vitamin B2 (riboflavin)	Liver, meat, whole grain cereals, yeast extract	Needed for metabolism of all food and release of energy to cell	Severe and cracking lips corner of the mouth
Vitamin B3 (niacin)	Nuts, fish, meat, yeast extract, unpolished rice	Needed by enzyme to convert food into energy	Pellagra, a disease characterized by skin lesions, loss of appetite and muscle weakness
Vitamin B6 (pyridoxine)	Meat, vegetables, yeast extracts, whole grain cereals	Essential in protein metabolism	Nerve irritability, sores in the mouth, eyes and anemia
Vitamin B12 (cobalamin)	Fish, meat, eggs, milk and liver	Builds genetic material, helps to form blood cells	Anemia, nerve damage, weight loss
Vitamin C (ascorbic acid)	Citrus fruits, fresh green vegetables and tomatoes	Antioxidant, improves absorption of iron, used in synthesis of collagen in the bones and gums	Muscle weakness, easy bruising, joint pains, scurvy (bleeding gums), poor healing of wounds and frequent infection
Vitamin D	Egg yolk, milk, oily fish and liver	Helps to build and maintain teeth and bones	Rickets in children, osteoporosis (soft bones) in adult
Vitamin E	Corn or sunflower oil, butter, brown rice and peanuts	Antioxidant prevents damage of all membranes	Nerve abnormalities, infertility in rats
Vitamin K	Green vegetables and liver	Needed for normal clotting	Defective blood coagulation resulting in excessive bleeding

Roughage

This dietary fiber is obtained from the indigestible parts of plants.

Sources of roughage

Foods such as fruits, beans, cabbage, spinach, cassava, and whole baked potatoes are good sources of roughage.

Functions of roughage

It helps in the passage of food and feces through the gut by aiding contraction of the gut muscles.

Water

This is a compound containing element hydrogen and oxygen.

Sources of water

Rainfall, rivers, springs, etc.

Functions of water

1. Used in digestion of food.
2. Used in transport of material in the body.
3. Used as solvent in chemical reaction.

Minerals

Certain mineral elements are vital for the proper functioning of the body. Some are required in relatively large quantities and are therefore called macro minerals. Others are required in very small quantity are referred to as micro minerals or trace elements.

The following are examples of minerals, their sources and their functions in the body.

i. Macro minerals

Minerals	Source	Function	Deficiency symptoms
Calcium	Milk, yoghurt, cheese, sardines, egg, green vegetables	Helps build strong bones and teeth, promote muscle and nerve functions, and important in clotting of blood	Weak bones, bleeding easily
Phosphorus	Meat, milk, fish, eggs and nuts	Builds bones and teeth, helps muscle and nerve activity, aids formation of genetic materials	Impaired nerve activity, bone and teeth formation
Potassium	Peanuts, bananas, orange juice, green beans and meat	Helps maintain regular fluid balance needed for nerve and muscle	Poor muscle contraction
Iron	Liver, meat, beans and green vegetables	Essential for formulating hemoglobin (the red pigment in blood)	Anemia
Zinc	Oysters, shrimp, crab, meat, yeast extracts	Activates enzymes, helps to heal wounds, necessary for a healthy immune system	Impaired teeth, poor immune response, skin problems
Sodium	Table salt	Necessary for nerve and muscle activity	Muscle cramps
Chlorine	Table salt	Maintenance of water and ionic balance, formation of hydrochloric acid in the stomach	Poor digestion of proteins
Magnesium	Spinach, pumpkin seeds, sesame seeds and black beans	Relaxation of nerves and muscle, strengthening of bones	Muscle weakness, irregular heartbeat and weaker bones

ii. Micro minerals

Minerals	Source	Function	Deficiency symptoms
Iodine	Iodinated table salt and seafood	Production of thyroid hormone which regulates growth, development of bones and teeth, helps prevent tooth decay	Goiter (enlarged thyroid gland)
Fluoride	Fluorinated water and fluoride tablets	Development of bones and teeth, helps prevent tooth decay	Poor development of bones and teeth, tooth decay
Manganese	Kidneys, liver, tea, coffee, nuts and fruit	Formation of bones and activation of enzymes	Nausea, dizziness, loss of hearing, loss of bone mass
Copper	Meat, fish and liver	Synthesis of bones and haemoglobin, activation of enzymes	Bleeding under skin, easy rupturing of blood vessels, bones and joint problems, anemia