Nutritional functions and sources of Proteins

Nutritional Functions and Sources of Proteins

• Proteins are vital for both structural and functional roles in body cells.
• Proteins are responsible for building the body's structure, including cartilage, muscles, skin, and hair.
• Protein is necessary for the body to grow, and to repair damaged or old cells.
• Antibodies, which are proteins, support the immune system in preventing infection.
• Enzymes are proteins and function as catalysts to accelerate reactions in the body.
• Certain hormones are proteins, acting as chemical messengers.
• Proteins can be utilized for energy if other energy sources like carbohydrates and fats are insufficient.

What Are Proteins?

• Amino acids are the building blocks of proteins, containing carbon, hydrogen, oxygen, and nitrogen, and sometimes sulphur.
• The radical (R) group is what makes each amino acid different.

Sources of Proteins

• Protein content varies widely in foods, and protein quality is based on how much and how its eaten.

Essential and Nonessential Amino Acids

• Proteins break down into amino acids during digestion to synthesize new proteins.
• The human body can produce non-essential (or dispensable) amino acids on its own.
• Essential (or indispensable) amino acids must be obtained through the diet.

Essential Amino Acids

• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine

Additional Amino Acids

• Children need histidine during growth.
• Arginine is also considered essential for children because they synthesize it slowly.

HBV and LBV Proteins

• Both animal and plant cells contain protein.
• High Biological Value (HBV) proteins contain essential amino acids in human proportions.
• Low Biological Value (LBV) proteins are deficient in one or more essential amino acids.
• The limiting amino acid is the one present in the shortest supply relative to the need.
• Animal-sourced proteins generally have higher HBV.
• Lysine is the limiting amino acid in wheat protein, tryptophan in maize protein, and methionine and cysteine in beef protein.
• Soya protein is the most complete among the vegetable sources.

Protein Complementation

• Proteins action can be complementary.
• When consuming vegetable proteins, combining a cereal (like bread) with a pulse (like beans) can compensate for the limitations of each, creating a higher biological value combination.

Nutritional Functions and Sources of Carbohydrates

• Carbohydrates provides energy, with 1g yielding 16 kJ (4 kcal).
• Sugars and starches (carbohydrates) break down into glucose during digestion.
• Glucose is stored as glycogen.
• Glycogen is converted back to glucose when the body needs it.
• Glucose is transported through the bloodstream to cells for energy.
• Amino acids from protein can serve as an energy source when other sources are limited.

Classification of Carbohydrates - Monosaccharides and Disaccharides

• Carbohydrates provide energy.

Structure of Carbohydrates:

Categorized into monosaccharides, disaccharides, and polysaccharides.

Monosaccharides:

• Single sugar molecules including glucose, fructose, and galactose, which make up other sugars in foods.

Disaccharides:

• Consist of pairs of monosaccharides, including sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose).

Classification of Carbohydrates - Polysaccharides

• Polysaccharides are formed by joining monosaccharides in long chains.
• Starch is a polysaccharide comprising amylose (straight glucose chains) and amylopectin (branched glucose chains).
• Glycogen is a glucose polysaccharide storing glucose in the liver and muscles, used when extra glucose is needed.
• Pectin is a non-starch polysaccharide (NSP) in fruits and vegetables that acts as a gelling agent in jams.
• Cellulose (NSP) cannot be broken down during digestion.

Polysaccharides Continued - Starch

• Amylose is an unbranched chain of glucose units.
• Amylopectin is a branched chain of glucose units.

Non-Starch Polysaccharides (NSP)

• Dietary carbohydrates are not digested by enzymes in the alimentary tract, but bacteria in the colon can digest it.

Carbohydrates as Staple Foods

• Staple foods are frequently eaten as part of a daily diet.
• Staple foods are readily available to the population at a low cost.
• They provide a major source of energy.
• They are generally high in starch.
• They provide some protein and micronutrients.
• Examples of staple foods include: rice, wheat, cassava, corn, plantains, potatoes and quinoa.

Intrinsic and Extrinsic Sugar

• Intrinsic sugars are naturally integrated into the cellular structure of foods like whole fruits and vegetables.
• Extrinsic sugars are free in food or added.
• Milk sugar (lactose) is an extrinsic sugar.
• Non-milk extrinsic sugars (NMES) include fruit juice, honey, and sugar when added during food creation.

Nutritional Functions and Sources of Fats

• Fats provide 37 kJ (9 kcal) per gram, making them energy-rich.
• Fat acts as an insulating layer under the skin and protects vital organs.
• Fats transport fat-soluble vitamins A, D, E, and K.
• Essential fatty acids keep hair and skin from drying out.

Triglycerides

• Triglycerides are the main part of fats and oils and comprises glycerol and free fatty acids.

Classifications of Fats

• Essential fatty acids must be obtained from the diet. Bodies cannot synthesize it.
• Saturated fatty acids lack any double bonds between carbon atoms.
• Unsaturated fatty acids have double bonds between carbon atoms.

Cholesterol

• Body cells need cholesterol to create bile acids for digesting fats, absorbing/using fats from food, and making hormones.
• The liver can produce cholesterol, and it is in animal foods, and bodies reduce cholesterol production when cholesterol is consumed.
• Saturated fat intake elevates blood cholesterol and may increase heart disease.

Sources of Fats

Animal Sources:

• Meat (visible and invisible fat), fatty fish and fish liver oils, and dairy products like butter and cream cheese.

Plant Sources:

• Include fruits and vegetables like avocados and olives, nuts like brazil nuts and walnuts, seeds like sesame and sunflower seeds, and other sources like palm and coconut.

Essential Fatty Acids

• A diet lacking fats can lead to illness.
• Essential fatty acids can't be produced by the body.

Three Essential Fatty Acids:

• Linolenic acid
• Linoleic acid
• Arachidonic acid
• Fish, nuts, seeds, and green vegetables contain omega-3 and omega-6 fatty acids.

Malnutrition

• Malnutrition rises from an imbalance in nutrient supply.

Two Categories of Malnutrition:

• Overnutrition and undernutrition.
• Overnutrition stems from consuming too much of one or more nutrients, commonly through energy imbalance.
• Undernutrition arises from insufficient intake of one or more nutrients, often linked to poverty (crop failure), or instability, anorexia can lead to undernutrition.