Carbohydrates, proteins, lipids, water, vitamins, and minerals are the main nutrients. Carbohydrates include sugars, starches, and fiber. They provide energy, aid protein use, and are found in fruits, vegetables, grains, and dairy. Proteins build tissues and aid functions; essential amino acids must come from diet. Lipids provide energy storage and insulation; fats can be saturated or unsaturated. Water regulates functions and temperature; dehydration causes thirst and fatigue. Non-starch polysaccharides aid digestion and prevent disease. Nutrients work together as coenzymes to control metabolic reactions.

1. Carbohydrates
Elements: Carbon – Hydrogen – Oxygen
Structure:
• Smallest molecule- Monosaccharide simplest units (glucose, fructose,
galactose) C6 H12 O6
• Disaccharides union of two monosaccharide (maltose with two glucose,
sucrose with a glucose and a fructose , lactose union of glucose and
galactose)
• Polysaccharides- long chain of monosaccharide (starch is a long chain
of glucose in plants, glycogen long chain of glucose in animals formed in
liver and muscles, NSP non starch monosaccharide or Dietary Fiber)
Functions:
• provide energy
• store energy as glycogen
• to be protein spares protecting proteins from being consumed for
energy so they are used for primary functions (repair and build
tissues) Total caloric value * 15-50% proteins
* 50-55 % carbohydrates
* 20% fats
Effect of heat:
* Sugar with dry heat melts, changes color, caramelizes and burns.
* Sugar with moist heat dissolves; water evaporates, melts, caramelizes
and burns.
* Starch with dry heat dextrinizes and partially digests (toast in the
oven).
* Starch with moist heat gelatinizes and absorbs water and swells (rice).
Food sources:
Glucose in fruits, honey, sugar.
Sucrose in sugar and fruits.
Lactose in milk and milk products
Starch in cereal and cereal products like bread, potatoes, …
Proteins
Elements: Carbon, Hydrogen, Oxygen, Nitrogen, Sulphur.
Structure: proteins are long chain of aminoacids (smallest units) which
combines to form millions of proteins.
Essential aminoacids: body can not build them up and have to be provided
by diet
* 10 essential aminoacids in children (growth).

2. * 8 essential aminoacids in adults.
High biological value protein (HBVP) or Complete protein: contains all the
essential aminoacids. Found in animal foods (egg white, fish …) and in soya
bean.
Low biological value protein (LBVP) or Incomplete protein: lacks one or
more essential aminoacid. Found in plant foods (cereals, legumes) and in
gelatine.
Protein complementation: combine to LBVP foods so the aminoacid missing
in one is provided by the other, increasing the final biological value of
that dish. Ex: cereals + legumes (in a stew rice with lentils).
Functions:
• Primary: build, repair and maintains tissues.
Transport substances like oxygen, fats, iron.
Form enzymes, antibodies, hormones.
• Secondary: provide energy after being deaminated in the body.
Coagulation: when proteins change their structure and set, they become
firmer, stronger in structure, consistent. Due to:
• Heat: ovoalbumin a protein present in egg white turns solid and white
at 60 degrees C.
• Mechanical agitation: When whisking egg whites. Salt aids coagulation.
• Acid: add an acid to milk, caseinogen clots.
• Freezing: mousse.
Lipids
Elements: Carbon, hydrogen, Oxygen, Phosphorus.
Structure: 1 glycerol + 3 fatty acids.
Fatty acids can be:
• saturated: all carbon atoms saturated with hydrogen, no double bonds
between carbon atoms. Molecules between 4 and 24 carbon atoms.
They raise cholesterol in humans. Found in animal sources (visible and
invisible fats) and coconut. Ex: butyric (butter), palmitic, stearic
(beef fat), lauric.
• unsaturated: double bonds present between carbon atoms.
*monounsaturated: one double bond between carbon
atoms. Ex: olive oil. Present in plats and it lowers cholesterol in humans.
*polyunsaturated: more than one double bond between
carbon atoms. Vegetable oils in nuts and seeds, and oily fish oils.
Functions:
• good source of energy (9 kcal per gram of fat) stored in fatty tissues
(long term storage of energy).

3. • Surround and protects vital organs.
• Forms an insulating layer under skin preserving body temperature.
• Provides source of fat soluble vitamin (ADEK).
• Provide texture and flavour in food to make it palatable.
• Gives a feeling of fullness (satiety) after meal, as fat digestion is
slow.
Effect of heat:
Solid fat melts with heat and becomes liquid oil. At a very high
temperature fat molecules decompose into glycerol and fatty acids.
Smoking point: not healthy for body. Different fats contain different
smoking points.
Fried foods absorb fat increasing the energy value. Fat soluble vitamins
are not affected by heat.
Non starch polysaccharides (NSP) or dietary fiber
Not digested by digestive enzymes (partially digested in colon by
bacteria).
Functions:
• stimulate peristaltic movements in intestine preventing constipation.
• Prevent colon cancer keeping the intestine healthy.
• Slow down absorption of glucose and cholesterol, reducing the
glycemic index (prevents obesity).
• Prevents diverticular disease and hemorrhoids.
• Provides a sense of fullness, foods remain longer in the intestine.
Food sources: whole grain cereals and its products, fruits and vegetables
with skin.
Water
Functions:
• for all metabolic and chemical reactions in the cells. It forms the
cytoplasm of the cell.
• Transport substances, absorb nutrients, and release waste products.
• Regulate body temperature (70 % of the body).
• Keep respiratory system moist and free from infections.
• Lubricate joints, eyes, etc.
Water Balance: (input – output)
Input : liquid drank, water in food. 2 litres a day (no kcal-no energy value).
Output: transpiration, urine, faeces, vomiting, diahorrea, fever.

4. Extra needs: physical activity, hot weather, babies, old people, pregnancy,
lactation, during illness due to fever, vomiting, diahorrea, temperature
control.
If water is lost in excess, patient suffers from DEHYDRATION: thirst,
dry lips and skin, sunken fontanellas in newborn, fatigue, tiredness, no
tears, headache, poor urination, sunken eyes.
Rehydration: water, salt, glucose. Water is absorbed faster in the presence
of glucose and sodium.
Vitamins and Minerals
Chemical substances which are vital for body.
Coenzymes: maintain growth of the body and control metabolic reactions in
cells.