BSC SEM 1 UNIT 3 APPLIED NUTRITION AND DIETETICS

Composition of Protein

Introduction

Proteins are vital macronutrients essential for growth, repair, and various physiological functions in the human body. They are made up of amino acids, which are the fundamental building blocks of life. Understanding the composition of proteins is crucial for nursing and healthcare professionals to provide optimal nutritional care to patients.

1. Composition of Proteins

Proteins are composed of the following elements:

Carbon (C) – 50–55%
Hydrogen (H) – 6–7%
Oxygen (O) – 20–23%
Nitrogen (N) – 15–18% (This is the distinguishing element of proteins)
Sulfur (S) – 0.5–2% (Present in some amino acids like cysteine and methionine)
Phosphorus (P) – Trace amounts (Found in some specialized proteins like casein)

These elements combine to form amino acids, which link together via peptide bonds to form proteins.

2. Amino Acids: The Building Blocks of Proteins

Proteins are made up of 20 different amino acids, which are classified into three categories:

A. Essential Amino Acids (Indispensable Amino Acids)

Definition: These amino acids cannot be synthesized by the human body and must be obtained from the diet.
List of Essential Amino Acids (Mnemonic: PVT TIM HALL)
1. Phenylalanine
2. Valine
3. Tryptophan
4. Threonine
5. Isoleucine
6. Methionine
7. Histidine (Essential for infants)
8. Arginine (Essential for infants)
9. Leucine
10. Lysine

B. Non-Essential Amino Acids (Dispensable Amino Acids)

Definition: These amino acids can be synthesized by the body.
Examples:
- Alanine
- Aspartic acid
- Asparagine
- Glutamic acid
- Serine

C. Conditionally Essential Amino Acids

Definition: These amino acids are usually non-essential but become essential in certain conditions, such as illness, stress, or metabolic disorders.
Examples:
- Arginine
- Cysteine
- Glutamine
- Tyrosine
- Proline
- Glycine

3. Protein Structure

Proteins have four levels of structure that determine their function:

A. Primary Structure

The linear sequence of amino acids in a polypeptide chain.

B. Secondary Structure

Folding of the polypeptide chain due to hydrogen bonding.
Examples:
- Alpha-helix (e.g., keratin in hair and nails)
- Beta-pleated sheets (e.g., silk proteins)

C. Tertiary Structure

Three-dimensional folding of the protein due to interactions between side chains (R-groups).
Determines the functionality of the protein (e.g., enzymes, hormones).

D. Quaternary Structure

Complex structure formed by multiple polypeptide chains.
Example: Hemoglobin (made of four polypeptide chains).

4. Classification of Proteins Based on Composition

Proteins are classified into different types based on their chemical composition:

A. Simple Proteins

Made up of only amino acids.
Examples:
- Albumin (found in egg white, blood plasma)
- Globulin (found in blood and milk)
- Collagen (found in connective tissues)

B. Conjugated Proteins

Contain a non-protein group (prosthetic group) along with amino acids.
Examples:
- Glycoproteins – Protein + Carbohydrate (e.g., mucin)
- Lipoproteins – Protein + Lipid (e.g., HDL, LDL)
- Phosphoproteins – Protein + Phosphate (e.g., casein in milk)
- Hemoproteins – Protein + Iron (e.g., hemoglobin)
- Nucleoproteins – Protein + Nucleic Acid (e.g., ribosomes)

C. Derived Proteins

Breakdown products of proteins.
Examples:
- Peptones
- Proteoses

5. Classification of Proteins Based on Function

Proteins serve various physiological roles, classified into:

Type of Protein	Function	Examples
Structural Proteins	Provide support	Collagen, Keratin
Enzymatic Proteins	Catalyze biochemical reactions	Amylase, Pepsin
Transport Proteins	Carry molecules	Hemoglobin, Albumin
Hormonal Proteins	Regulate metabolism	Insulin, Growth Hormone
Immune Proteins	Defense against infections	Antibodies (Immunoglobulins)
Contractile Proteins	Muscle contraction	Actin, Myosin
Storage Proteins	Store amino acids	Ferritin (iron storage), Casein (milk protein)

6. Protein Metabolism

Protein metabolism involves digestion, absorption, and utilization of proteins.

A. Digestion of Proteins

Mouth – No digestion of proteins.
Stomach – Enzyme pepsin breaks down proteins into polypeptides.
Small Intestine:
- Pancreatic enzymes: Trypsin, Chymotrypsin, Carboxypeptidase further break down polypeptides.
- Intestinal enzymes: Peptidases convert polypeptides into amino acids.

B. Absorption

Amino acids are absorbed into the bloodstream through the small intestine and transported to the liver.

C. Utilization

Proteins are used for:
- Tissue repair and growth
- Enzyme and hormone production
- Energy production (if carbohydrate and fat intake is insufficient)

D. Deamination and Excretion

Excess amino acids undergo deamination in the liver, producing ammonia, which is converted into urea and excreted via the kidneys.

7. Importance of Protein in Nursing and Healthcare

Wound Healing – Proteins are crucial for tissue repair post-surgery or injury.
Malnutrition Management – Nurses must identify and manage protein-energy malnutrition (PEM) like kwashiorkor and marasmus.
Critical Care Nutrition – Patients in ICU, burn units, or recovering from infections require high protein intake.
Geriatric Care – Elderly patients need adequate protein to prevent muscle wasting (sarcopenia).
Maternal and Child Health – Pregnant and lactating women require increased protein intake for fetal growth and milk production.

Classification of Proteins –

Proteins are essential macronutrients that perform various structural, enzymatic, and regulatory functions in the body. Based on their structure, function, and composition, proteins can be classified into different categories.

1. Classification Based on Composition

Proteins are classified into three main types based on their chemical composition:

A. Simple Proteins

Composed only of amino acids.
Yield only amino acids upon hydrolysis.
Examples:
- Albumins (egg white, blood plasma)
- Globulins (antibodies, muscle proteins)
- Histones (found in DNA)
- Protamines (sperm cells)
- Glutelins (wheat gluten)

B. Conjugated Proteins

Composed of amino acids plus a non-protein component (prosthetic group).
The prosthetic group determines the function of the protein.
Examples:
- Glycoproteins – Protein + Carbohydrate (e.g., mucin in mucus)
- Lipoproteins – Protein + Lipid (e.g., HDL, LDL in blood)
- Phosphoproteins – Protein + Phosphate (e.g., casein in milk)
- Hemoproteins – Protein + Iron (e.g., hemoglobin, myoglobin)
- Nucleoproteins – Protein + Nucleic Acid (e.g., ribosomes)

C. Derived Proteins

Breakdown products of proteins formed during digestion or metabolism.
Examples:
- Peptones – Intermediate breakdown products of proteins.
- Proteoses – Partially digested proteins.
- Polypeptides – Short chains of amino acids.

2. Classification Based on Structure

Proteins can be classified into two main structural types:

A. Fibrous Proteins

Long, insoluble, and structural in function.
Provide mechanical support and strength.
Examples:
- Collagen – Found in connective tissue, bones, skin.
- Keratin – Found in hair, nails, and outer skin.
- Elastin – Provides elasticity in ligaments and skin.
- Myosin – Found in muscle fibers.

B. Globular Proteins

Spherical, soluble in water, and perform dynamic functions.
Examples:
- Enzymes (e.g., amylase, pepsin)
- Hormones (e.g., insulin, growth hormone)
- Hemoglobin – Oxygen transport in blood.
- Immunoglobulins – Antibodies in immune response.

3. Classification Based on Function

Proteins are classified based on their role in the body:

Type of Protein	Function	Examples
Structural Proteins	Provide support and shape	Collagen, Keratin
Enzymatic Proteins	Catalyze biochemical reactions	Amylase, Pepsin
Transport Proteins	Carry molecules across the body	Hemoglobin, Albumin
Hormonal Proteins	Regulate metabolic processes	Insulin, Growth Hormone
Immune Proteins	Defend against infections	Immunoglobulins (Antibodies)
Contractile Proteins	Muscle contraction and movement	Actin, Myosin
Storage Proteins	Store essential molecules	Ferritin (Iron), Casein (Milk Protein)

4. Classification Based on Nutritional Value

Proteins are classified based on their ability to provide essential amino acids.

A. Complete Proteins

Contain all essential amino acids in the right proportion.
Mostly from animal sources.
Examples:
- Meat, Fish, Eggs, Milk, Cheese, Soybeans, Quinoa.

B. Incomplete Proteins

Lack one or more essential amino acids.
Mostly from plant sources.
Examples:
- Legumes, Grains, Nuts, Vegetables.

C. Complementary Proteins

A combination of two or more incomplete proteins that together provide all essential amino acids.
Examples:
- Rice + Beans
- Wheat + Peanut Butter
- Corn + Lentils

5. Classification Based on Solubility

Proteins are categorized based on their solubility in different solvents.

Type of Protein	Solubility	Examples
Albumins	Soluble in water	Egg albumin, Serum albumin
Globulins	Insoluble in pure water, soluble in salt solutions	Immunoglobulins, Myosin
Glutelins	Soluble in dilute acids/alkalis	Gluten in wheat
Prolamins	Soluble in alcohol	Zein in corn, Gliadin in wheat
Scleroproteins	Insoluble in water, tough structural proteins	Collagen, Keratin

6. Classification Based on Source

Proteins are classified based on their origin.

A. Animal Proteins

High biological value.
Rich in essential amino acids.
Examples:
- Meat, Poultry, Fish, Eggs, Milk, Cheese.

B. Plant Proteins

Lower biological value but rich in fiber and phytochemicals.
Examples:
- Beans, Lentils, Chickpeas, Tofu, Nuts, Whole Grains.

7. Classification Based on Biological Value (BV)

Biological value (BV) refers to the percentage of absorbed protein that is utilized for body growth and maintenance.

A. High Biological Value (HBV) Proteins

Provide all essential amino acids in the right proportions.
Examples:
- Eggs (BV = 100)
- Milk (BV = 90)
- Meat & Fish (BV = 80-90)
- Soy Protein (BV = 74)

B. Low Biological Value (LBV) Proteins

Deficient in one or more essential amino acids.
Examples:
- Wheat (BV = 60)
- Rice (BV = 55)
- Beans & Lentils (BV = 50)

8. Classification Based on Protein Quality

A. Complete Proteins

Contain all essential amino acids.
Examples: Egg, Fish, Milk.

B. Partially Complete Proteins

Support maintenance but not growth.
Examples: Gelatin.

C. Incomplete Proteins

Cannot support maintenance or growth alone.
Examples: Zein in Corn.

9. Functional Properties of Proteins

Proteins have various properties that determine their role in food and biological systems.

Property	Function
Gel Formation	Forms gels when heated and cooled (e.g., gelatin in jelly).
Foaming	Creates foams in whipped cream and beaten egg whites.
Water Absorption	Retains moisture in food.
Emulsification	Helps in fat dispersion (e.g., egg yolk in mayonnaise).
Coagulation	Proteins coagulate when heated (e.g., curdling of milk).

Eight Essential Amino Acids

Introduction

Amino acids are the building blocks of proteins, essential for various physiological functions such as growth, repair, and enzyme production. Among the 20 amino acids required by the human body, eight are classified as essential amino acids because they cannot be synthesized by the body and must be obtained through diet.

List of Eight Essential Amino Acids

The eight essential amino acids are:

Phenylalanine
Valine
Threonine
Tryptophan
Methionine
Leucine
Isoleucine
Lysine

(Mnemonic: PVT TIM LL)

These amino acids are critical for protein synthesis, tissue growth, neurotransmitter function, and various metabolic processes.

Detailed Functions and Sources of Each Essential Amino Acid

1. Phenylalanine (Phe)

Functions:

Precursor for neurotransmitters dopamine, epinephrine, and norepinephrine.
Essential for the production of thyroid hormones.
Plays a role in pain relief and mood regulation.

Dietary Sources:

Meat (beef, chicken, fish)
Eggs
Dairy products (cheese, milk, yogurt)
Soybeans
Nuts and seeds (almonds, sunflower seeds)

Deficiency Symptoms:

Memory loss
Depression and mood disorders
Skin disorders like eczema

2. Valine (Val)

Functions:

Helps in muscle metabolism and growth.
Involved in energy production.
Plays a role in tissue repair.

Dietary Sources:

Meat (beef, poultry)
Dairy products (cheese, yogurt)
Peanuts and soy products
Whole grains (brown rice, oats)

Deficiency Symptoms:

Muscle weakness
Fatigue
Poor concentration

3. Threonine (Thr)

Functions:

Helps in the formation of collagen and elastin (important for skin and connective tissues).
Supports immune function.
Essential for fat metabolism in the liver.

Dietary Sources:

Meat and poultry
Dairy products
Nuts and seeds
Leafy green vegetables

Deficiency Symptoms:

Fatty liver
Impaired immune function
Digestive disorders

4. Tryptophan (Trp)

Functions:

Precursor for serotonin and melatonin (important for mood regulation and sleep).
Plays a role in niacin (Vitamin B3) production.
Helps in reducing stress and anxiety.

Dietary Sources:

Turkey and chicken
Fish
Dairy products
Nuts and seeds
Chocolate and bananas

Deficiency Symptoms:

Depression and anxiety
Sleep disturbances (insomnia)
Poor appetite

5. Methionine (Met)

Functions:

Involved in detoxification and metabolism.
A precursor for cysteine and glutathione (important antioxidants).
Supports hair and nail growth.

Dietary Sources:

Meat and fish
Dairy products
Eggs
Nuts and seeds
Beans and lentils

Deficiency Symptoms:

Fatty liver
Slow wound healing
Weak immune system

6. Leucine (Leu)

Functions:

Plays a critical role in muscle growth and repair.
Helps in wound healing.
Regulates blood sugar levels.

Dietary Sources:

Red meat
Dairy products
Peanuts
Lentils and chickpeas
Whole wheat products

Deficiency Symptoms:

Muscle wasting
Fatigue
Low energy levels

7. Isoleucine (Ile)

Functions:

Involved in muscle metabolism and immune function.
Helps in hemoglobin production.
Regulates blood sugar levels.

Dietary Sources:

Meat, fish, and poultry
Dairy products
Nuts and seeds
Whole grains

Deficiency Symptoms:

Muscle weakness
Dizziness and confusion
Poor immune function

8. Lysine (Lys)

Functions:

Essential for collagen formation (important for bones and skin).
Helps in calcium absorption.
Supports immune function and antibody production.

Dietary Sources:

Red meat and poultry
Fish (cod, sardines)
Dairy products
Legumes (beans, peas)
Quinoa

Deficiency Symptoms:

Poor immune function
Fatigue and dizziness
Hair loss

Importance of Essential Amino Acids in Nursing and Healthcare

Growth and Development – Essential for children, pregnant women, and recovering patients.
Muscle Maintenance – Helps prevent muscle atrophy in bedridden patients.
Immune System Support – Essential for fighting infections and diseases.
Wound Healing – Crucial in post-surgical recovery and burn patients.
Mental Health – Supports neurotransmitter production, reducing stress and anxiety.

Deficiency of Essential Amino Acids

If a person does not consume enough essential amino acids, it can lead to:

Growth retardation in children
Muscle loss and weakness
Poor immune function
Neurological issues such as confusion, depression, and anxiety
Fatty liver and metabolic disorders

Sources of Essential Amino Acids

To ensure adequate intake, one should consume:

Animal proteins (Complete Proteins): Meat, fish, eggs, dairy.
Plant-based proteins (Complementary Proteins):
- Legumes + Grains (e.g., rice and beans)
- Nuts + Whole Grains (e.g., peanut butter on whole wheat bread)

Dietary Sources of Protein

Protein is an essential macronutrient required for growth, repair, and maintenance of body tissues. It is found in both animal-based and plant-based foods, each providing different types of amino acids.

1. Animal-Based Sources of Protein (Complete Proteins)

Animal proteins are considered complete proteins because they provide all essential amino acids in the right proportions.

A. Meat and Poultry

Chicken (100g = 27g protein)
Turkey (100g = 29g protein)
Beef (100g = 26g protein)
Pork (100g = 25g protein)
Lamb (100g = 25g protein)

B. Fish and Seafood

Salmon (100g = 25g protein)
Tuna (100g = 30g protein)
Cod (100g = 20g protein)
Shrimp (100g = 24g protein)
Crab (100g = 19g protein)

C. Dairy Products

Milk (1 cup = 8g protein)
Cheese (Cheddar, Mozzarella, Cottage Cheese) (100g = 22–30g protein)
Yogurt (1 cup = 10g protein)
Butter (Low in protein but contains essential fats)

D. Eggs

Whole egg (1 large = 6g protein)
Egg whites (1 large = 3.5g protein)

2. Plant-Based Sources of Protein (Incomplete Proteins)

Plant-based proteins often lack one or more essential amino acids but can be combined to form complete proteins.

A. Legumes and Pulses

Lentils (100g cooked = 9g protein)
Chickpeas (Garbanzo Beans) (100g cooked = 8g protein)
Black Beans (100g cooked = 9g protein)
Kidney Beans (100g cooked = 8g protein)
Green Peas (100g cooked = 5g protein)

B. Nuts and Seeds

Almonds (100g = 21g protein)
Peanuts (100g = 26g protein)
Walnuts (100g = 15g protein)
Chia Seeds (100g = 17g protein)
Flaxseeds (100g = 18g protein)
Sunflower Seeds (100g = 21g protein)
Pumpkin Seeds (100g = 19g protein)

C. Whole Grains

Quinoa (100g cooked = 4g protein) (Complete protein)
Brown Rice (100g cooked = 3g protein)
Oats (100g cooked = 6g protein)
Whole Wheat Bread (1 slice = 3–5g protein)
Corn (100g = 3g protein)

D. Soy Products (Complete Plant Proteins)

Tofu (100g = 8g protein)
Tempeh (100g = 19g protein)
Soy Milk (1 cup = 7g protein)
Edamame (Young Soybeans) (100g = 11g protein)

E. Vegetables (Low but Important Protein Sources)

Spinach (100g cooked = 3g protein)
Broccoli (100g cooked = 2.8g protein)
Mushrooms (100g = 3g protein)
Brussels Sprouts (100g = 3g protein)
Asparagus (100g = 2g protein)

3. Protein Supplements

For individuals who need additional protein intake, supplements can be used.

A. Protein Powders

Whey Protein (High in leucine, used for muscle building)
Casein Protein (Slow-digesting protein, good for nighttime use)
Soy Protein (Plant-based alternative, good for vegetarians)
Pea Protein (Hypoallergenic, suitable for people with allergies)
Rice Protein (Lower in lysine but still beneficial)

4. Comparison of Protein Content in Different Sources

Food Item	Protein per 100g
Chicken Breast	27g
Beef	26g
Salmon	25g
Tuna	30g
Eggs (whole)	6g (per egg)
Milk	8g (per cup)
Cheese (Cheddar)	25g
Lentils	9g
Chickpeas	8g
Tofu	8g
Almonds	21g
Peanuts	26g
Quinoa	4g
Broccoli	2.8g

5. Combining Plant-Based Proteins for a Complete Amino Acid Profile

Since most plant-based proteins are incomplete proteins, they should be combined to ensure all essential amino acids are consumed.

Food Combination	Example Dishes
Legumes + Grains	Rice and Beans, Dal with Roti
Grains + Nuts/Seeds	Oatmeal with Almonds, Bread & Peanut Butter
Vegetables + Seeds	Spinach Salad with Sunflower Seeds
Soy + Whole Grains	Tofu with Brown Rice

6. Choosing the Right Protein Sources for Different Diets

Diet Type	Best Protein Sources
Vegetarian	Dairy, eggs, legumes, nuts, seeds, quinoa, soy products
Vegan	Legumes, soy, nuts, seeds, whole grains, vegetables
Keto Diet	Meat, fish, eggs, cheese, nuts, low-carb vegetables
Weight Loss	Lean meats, fish, egg whites, legumes, soy products
Muscle Building	Chicken, beef, fish, eggs, dairy, whey protein

7. Protein Requirements for Different Age Groups

Category	Recommended Daily Allowance (RDA)
Infants (0-1 year)	1.5 g/kg body weight
Children (1-10 years)	1.0 g/kg body weight
Adolescents (11-18 years)	0.9 g/kg body weight
Adults	0.8 g/kg body weight
Pregnant Women	1.1 g/kg body weight
Lactating Women	1.3 g/kg body weight
Athletes & Bodybuilders	1.2 – 2.0 g/kg body weight

Functions of Proteins

Proteins play a crucial role in the human body, performing various structural, regulatory, and metabolic functions. Since proteins are made up of amino acids, they serve as building blocks for different body tissues and biological processes.

1. Structural Functions

Proteins are essential for the structure and strength of body tissues.

A. Body Tissue Formation

Proteins provide structural support to muscles, bones, skin, hair, and nails.
Example: Collagen (found in connective tissues) provides strength to bones, skin, and tendons.

B. Growth and Development

Necessary for growth during childhood, adolescence, pregnancy, and muscle repair.
Example: Keratin strengthens hair, nails, and the outer layer of skin.

2. Enzymatic Functions

Enzymes are specialized proteins that catalyze biochemical reactions, speeding up metabolism.

Example: Pepsin (digests proteins in the stomach).
Example: Amylase (breaks down carbohydrates into sugars).

Without enzymes, metabolic processes would be too slow to sustain life.

3. Transport and Storage Functions

Proteins help in the transportation and storage of important molecules in the body.

A. Transport Proteins

Hemoglobin transports oxygen from the lungs to tissues.
Albumin carries hormones, fatty acids, and drugs in the blood.
Transferrin transports iron to different body tissues.

B. Storage Proteins

Ferritin stores iron in the liver.
Casein stores protein in milk for infant nutrition.

4. Immune Functions (Defense Mechanism)

Proteins play a key role in the body’s immune system by forming antibodies.

Immunoglobulins (Antibodies) help fight infections by identifying and neutralizing bacteria, viruses, and toxins.
Complement Proteins enhance immune response.

Without proteins, the body would be unable to defend itself against diseases.

5. Hormonal Functions (Regulatory Role)

Proteins help regulate bodily functions by producing hormones.

Insulin regulates blood sugar levels.
Thyroxine regulates metabolism.
Growth Hormone stimulates body growth and cell regeneration.

Protein-based hormones ensure homeostasis and proper organ function.

6. Contractile and Movement Functions

Proteins play an essential role in muscle contraction and body movement.

Actin and Myosin in muscle fibers enable muscle contraction.
Help in movements like walking, breathing, and heartbeat.

Without proteins, muscle strength and mobility would be compromised.

7. Energy Source

Proteins act as an energy reserve when carbohydrates and fats are insufficient.

1 gram of protein provides 4 kcal of energy.
During starvation, the body breaks down muscle proteins for energy.

However, excess protein consumption for energy may lead to kidney strain and dehydration.

8. Buffering Function (Acid-Base Balance)

Proteins help maintain the pH balance in the body.

Hemoglobin in the blood acts as a buffer to maintain pH.
Plasma proteins (e.g., albumin) prevent excessive acidity or alkalinity.

Without this function, acidic blood conditions (acidosis) or alkaline conditions (alkalosis) could occur, leading to organ damage.

9. Fluid Balance Maintenance

Proteins regulate osmotic pressure, preventing excess fluid loss from the blood.

Albumin and Globulin maintain blood volume and fluid distribution.
Prevents conditions like edema (swelling due to fluid retention).

A lack of protein leads to malnutrition-related edema, seen in Kwashiorkor.

10. Wound Healing and Tissue Repair

Proteins help repair tissues and heal wounds by generating new cells.

Fibrinogen helps in blood clotting.
Collagen helps in wound healing and skin regeneration.

Patients recovering from surgery, burns, or injuries require high protein intake.

11. Reproductive and Fetal Development

Proteins are essential for fetal growth and milk production during pregnancy and lactation.

Casein in breast milk supports infant growth.
Hormones like prolactin regulate milk production.

Pregnant and lactating women need higher protein intake to support both mother and baby.

Summary Table: Functions of Proteins

Function	Examples
Structural Support	Collagen, Keratin
Growth & Development	Muscle, Hair, Skin
Enzymatic Reactions	Pepsin, Amylase
Transport	Hemoglobin (Oxygen), Albumin (Nutrients)
Storage	Ferritin (Iron), Casein (Milk)
Immune Defense	Immunoglobulins (Antibodies)
Hormone Regulation	Insulin, Growth Hormone
Muscle Contraction	Actin, Myosin
Energy Source	Used when carbs/fats are low
Acid-Base Balance	Hemoglobin, Plasma Proteins
Fluid Balance	Albumin (Prevents Edema)
Wound Healing	Fibrinogen (Clotting), Collagen
Reproductive Functions	Prolactin (Lactation)

Protein Requirements – Recommended Dietary Allowance (RDA)

Introduction

Protein is an essential macronutrient required for growth, repair, immune function, enzyme production, and overall metabolism. The Recommended Dietary Allowance (RDA) for protein varies based on age, sex, physiological condition, and activity level. The RDA is expressed as grams of protein per kilogram (g/kg) of body weight per day.

1. Protein Requirements Based on Age and Gender

A. Infants and Children

Protein is crucial for growth and development in infants and children.

Age Group	RDA (g/kg body weight/day)	Total Daily Requirement
0 – 6 months	1.5 g/kg	9–15g (Based on average weight)
6 – 12 months	1.2 g/kg	11–18g
1 – 3 years	1.05 g/kg	13g
4 – 8 years	0.95 g/kg	19g
9 – 13 years	0.85 g/kg	34g

B. Adolescents

Adolescents require higher protein intake due to rapid growth and hormonal changes.

Age Group	RDA (g/kg body weight/day)	Total Daily Requirement
Boys (14–18 years)	0.85 g/kg	52g
Girls (14–18 years)	0.85 g/kg	46g

C. Adults

Adult protein requirements are based on body maintenance and metabolism.

Age Group	RDA (g/kg body weight/day)	Total Daily Requirement
Men (19–50 years)	0.8 g/kg	56g
Women (19–50 years)	0.8 g/kg	46g
Men (51+ years)	0.8 g/kg	56g
Women (51+ years)	0.8 g/kg	46g

2. Protein Requirements for Special Groups

A. Pregnant and Lactating Women

Pregnant and breastfeeding women require additional protein for fetal growth, milk production, and maternal health.

Condition	RDA (g/kg body weight/day)	Total Daily Requirement
Pregnancy (1st trimester)	0.8 g/kg	46g
Pregnancy (2nd & 3rd trimester)	1.1 g/kg	71g
Lactation (0–6 months)	1.3 g/kg	71g
Lactation (6–12 months)	1.3 g/kg	71g

B. Elderly Individuals

Older adults require higher protein intake to prevent muscle loss (sarcopenia) and maintain immune function.

Age Group	RDA (g/kg body weight/day)	Total Daily Requirement
60+ years	1.0 – 1.2 g/kg	50–75g

C. Athletes and Bodybuilders

Athletes need more protein for muscle repair, endurance, and strength building.

Activity Level	RDA (g/kg body weight/day)
Sedentary person	0.8 g/kg
Endurance athletes	1.2 – 1.4 g/kg
Strength/Power athletes	1.6 – 2.0 g/kg
Bodybuilders (Muscle gain phase)	1.6 – 2.2 g/kg

3. Protein Requirements Based on Body Weight

Protein needs can be calculated using body weight. The formula:

Protein Requirement (g) = Body Weight (kg) × RDA (g/kg body weight)

Examples of Daily Protein Needs:

Body Weight	Sedentary (0.8 g/kg)	Athlete (1.5 g/kg)	Bodybuilder (2.0 g/kg)
50 kg	40g	75g	100g
60 kg	48g	90g	120g
70 kg	56g	105g	140g
80 kg	64g	120g	160g

4. Effects of Protein Deficiency and Excess

A. Protein Deficiency (Hypoproteinemia)

Lack of sufficient protein intake leads to:

Growth retardation (in children)
Muscle wasting (loss of lean body mass)
Edema (fluid retention, seen in Kwashiorkor)
Weakened immunity (frequent infections)
Fatty liver (due to poor metabolism)

B. Excess Protein Intake

Consuming excessive protein can cause:

Kidney strain (excess nitrogen excretion)
Dehydration (due to high urea production)
Increased calcium loss (risk of osteoporosis)
Weight gain (if excess protein is converted to fat)

5. Best Dietary Sources of Protein

A. Animal-Based Protein Sources (Complete Proteins)

Chicken (100g = 27g protein)
Fish (100g = 25g protein)
Eggs (1 large = 6g protein)
Milk (1 cup = 8g protein)
Cheese (100g = 25g protein)

B. Plant-Based Protein Sources (Incomplete Proteins)

Lentils (100g = 9g protein)
Chickpeas (100g = 8g protein)
Quinoa (100g = 4g protein – Complete Plant Protein)
Tofu (100g = 8g protein)
Nuts & Seeds (Almonds 100g = 21g protein)

6. How to Meet Daily Protein Requirements?

A. Balanced Meal Plan Example (For 60g Protein Intake)

Meal	Food Item	Protein Content (g)
Breakfast	2 eggs + whole wheat toast + 1 glass milk	18g
Mid-Morning Snack	Handful of almonds	6g
Lunch	Grilled chicken + brown rice + vegetables	25g
Evening Snack	Yogurt with chia seeds	8g
Dinner	Lentil soup + salad	12g

7. Adjusting Protein Intake for Special Cases

Condition	Adjustment Needed
Kidney Disease	Reduce protein intake (0.6-0.8 g/kg) to prevent kidney overload
Liver Disease	Moderate protein intake (0.8-1.2 g/kg) to support liver function
Burn or Trauma Patients	Increase protein intake (1.5-2.0 g/kg) for tissue repair
Weight Loss	High-protein, low-calorie diet (1.2-1.6 g/kg) to preserve muscle mass

Published March 2, 2025By mynursingapp

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