Essential Nutrients and Their Food Sources

Feeding is the selection, preparation, and ingestion of food. It is a conscious and voluntary process.

Nutrition is a set of processes which include digestion (nutrients contained in these foods are extracted), absorption of nutrients (from the intestines to blood), use by cell metabolism to produce energy and matter, and egestion (to eliminate waste products through the excretory system). These are unconscious and involuntary processes.

Inorganic Nutrients:

• Water: Is the most abundant nutrient in the body. It has a variety of functions:
  • Regulates body temperature.
  • Transports other nutrients and waste products through the body.

  All foods contain water. We should drink 1.5 liters daily.

• Mineral salts: They can be ions (Na, K, Fe, etc.) or solids (calcium carbonate). They take part in muscle contraction, nervous impulse movements, coagulation, forming bones, etc. Sources: vegetables, fruit, milk, etc.

Organic Nutrients:

• Carbohydrates:
  • Monosaccharides: i.e. glucose. They are the simplest carbohydrates; they are a type of sugar (they are sweet). They are used in cells to produce energy in the mitochondrion by cell respiration. They are in fruits.
  • Disaccharides: i.e. sucrose (sugar obtained from sugar cane, used by human beings to sweeten food). It consists of two monosaccharides. That is why disaccharides are used by organisms to produce energy.
  • Polysaccharides: Are a chain formed by many monosaccharides. Two examples:
    • Starch: Is an energy reservoir in plants (potatoes and cereals).
    • Glycogen: Is an energy reservoir in animals (it is stored in muscle or liver).
• Lipids: Are a group of nutrients that cannot be dissolved in water but can be dissolved in organic solvents like alcohol. For example, fats. Fats are stored in the adipocytes of fat tissue. Sources: oil, bacon, milk, etc.
• Proteins: Are molecules formed by a great number of units linked to each other called amino acids. They have a variety of functions:
  • Form structures.
  • Muscular contraction (myosin and actin).
  • Produce hormones (insulin).
  • Protect the body against illnesses (antibodies).
  • Transport substances (hemoglobin, which transports oxygen).
  • Control chemical reactions in cells (enzymes).

  Sources: meat, fish, milk, etc.

Fiber (cellulose, a type of polysaccharide) is not a nutrient as it cannot be digested (broken to release glucose) by the organism. That is why it is disposed of through the feces without undergoing any change.

Food Classification

Food can be classified depending on:

• The time it takes to spoil: Perishable (i.e., fish), semi-perishable (i.e., apple), and non-perishable (i.e., honey).
• Its origin: Animal (fish, egg, meat, etc.), plant (fruit, vegetable, etc.), mineral (water, salt).
• Its nutrient composition: The food wheel graphically represents the six different types of food:
  • Group 1: Pasta, cereals, potatoes, etc. They provide carbohydrates.
  • Group 2: Oil, butter, bacon, etc. They provide lipids.
  • Group 3: Meat, egg, fish, etc. They provide proteins.
  • Group 4: Milk, yogurt, cheese, etc. They provide proteins.
  • Group 5: Vegetables and legumes. They provide vitamins and mineral salts.
  • Group 6: Fruit. They provide minerals and vitamins.