Food Classes & Balanced Diet: A Comprehensive Guide

This note expands on the essential concepts of food classes, balanced diet, malnutrition, and deficiency diseases, providing detailed insights into each topic as outlined in the syllabus.

1. Classes of Food (Macronutrients and Micronutrients)

Food is broadly categorized into macronutrients and micronutrients, each playing a vital role in the body's proper functioning.

1.1 Macronutrients

These are required in large quantities and provide energy and building blocks for the body.

1.1.1 Carbohydrates

• Functions:
  • Primary Energy Source: Carbohydrates are the body's main source of energy, especially for the brain and muscles. Glucose, a simple sugar derived from carbohydrates, is the preferred fuel for most cells.
  • Energy Storage: Excess glucose can be stored as glycogen in the liver and muscles for later use.
  • Protein Sparing: Adequate carbohydrate intake prevents the body from breaking down proteins for energy, thus allowing proteins to perform their essential functions like building and repairing tissues.
  • Preventing Ketosis: Sufficient carbohydrates prevent the body from producing acidic ketone bodies, which can occur when fat is used as the primary energy source due to insufficient glucose.
• Sources: Grains (rice, wheat, oats), bread, pasta, potatoes, fruits, vegetables, legumes, and sugars.

1.1.2 Fats (Lipids)

• Functions:
  • Concentrated Energy Source: Fats provide more than double the energy content per gram compared to carbohydrates or proteins, serving as an important energy reserve.
  • Insulation and Protection: Fats insulate the body, helping to maintain body temperature, and protect vital organs from shock and injury.
  • Cell Membrane Component: They are crucial components of cell membranes, contributing to their structure and regulating fluidity.
  • Hormone Production: Fats are involved in the production and regulation of various hormones, including those important for reproductive health.
  • Absorption of Fat-Soluble Vitamins: Dietary fats are essential for the absorption and transport of fat-soluble vitamins (A, D, E, and K).
  • Nerve Function: Fats are important for brain activity, forming nerve cell membranes, insulating neurons, and facilitating electrical impulse signaling.
  • Flavor and Satiety: Fats contribute to the taste and texture of food and promote a feeling of fullness after meals.
• Sources: Oils (vegetable, olive, coconut), butter, nuts, seeds, avocados, fatty fish (salmon, mackerel), and dairy products.

1.1.3 Proteins

• Functions:
  • Building and Repairing Tissues: Proteins are fundamental for the growth, maintenance, and repair of all body tissues, including muscles, organs, skin, and hair.
  • Enzyme Production: Many proteins act as enzymes, which are biological catalysts that facilitate nearly all chemical reactions in the body, including digestion and metabolism.
  • Hormone Production: Some hormones, which act as chemical messengers, are proteins (e.g., insulin).
  • Structural Support: Proteins like keratin (in hair and nails) and collagen (in skin, bones, and tendons) provide structural support.
  • Transport and Storage: Transport proteins carry substances (e.g., oxygen via hemoglobin, nutrients, cholesterol) throughout the bloodstream and within cells. Storage proteins store essential substances (e.g., ferritin stores iron).
  • Immune Function: Antibodies, which are proteins, play a crucial role in the immune system by identifying and neutralizing foreign invaders like bacteria and viruses.
  • Fluid and pH Balance: Proteins help maintain proper fluid balance and regulate pH levels in the body.
  • Energy Source (Secondary): While not their primary role, proteins can be used as an energy source if carbohydrate and fat intake is insufficient.
• Sources: Meat, poultry, fish, eggs, dairy products, legumes (beans, lentils), nuts, and seeds.

1.2 Micronutrients

These are required in smaller quantities but are essential for various metabolic processes and overall health.

1.2.1 Mineral Salts

Mineral salts are inorganic substances vital for numerous bodily functions.

• Calcium:
  • Functions: Essential for strong bones and teeth, muscle contraction, nerve transmission, blood clotting, and hormone secretion.
  • Sources: Dairy products (milk, cheese, yogurt), leafy green vegetables (broccoli, kale), fortified foods.
• Iodine:
  • Functions: Crucial for the production of thyroid hormones (thyroxine and triiodothyronine), which regulate metabolism, growth, and development (especially brain development in infants and children).
  • Sources: Iodized salt, seafood, dairy products.
• Iron:
  • Functions: A vital component of hemoglobin (in red blood cells) for oxygen transport from the lungs to all body parts, and myoglobin (in muscles) for oxygen storage. Also involved in energy metabolism and immune function.
  • Sources: Red meat, poultry, fish, beans, lentils, spinach, fortified cereals.
• Sodium:
  • Functions: Helps maintain fluid balance, nerve impulse transmission, muscle contraction, and blood pressure regulation.
  • Sources: Table salt, processed foods, some natural foods.

1.2.2 Vitamins

Vitamins are organic compounds essential for normal growth and nutrition, required in small quantities in the diet because they cannot be synthesized by the body.

• Vitamin A (Retinol):
  • Sources: Liver, eggs, dairy, oily fish, and beta-carotene from yellow, red, and green leafy vegetables (carrots, spinach, sweet potatoes).
  • Functions: Essential for vision (especially in dim light), immune function, cell growth and differentiation, and maintaining healthy skin and mucous membranes.
  • Deficiency Diseases: Night blindness, xerophthalmia (leading to irreversible blindness), increased susceptibility to infections, dry skin.
• B Vitamins (B-complex): (e.g., B1 Thiamine, B3 Niacin, B12 Cobalamin)
  • Sources: Whole grains, meat, fish, eggs, dairy, legumes, leafy greens.
  • Functions: Play crucial roles in converting food into energy (metabolism), supporting red blood cell production, maintaining brain and nerve function, and overall cell health.
  • Deficiency Diseases:
    • Beriberi (B1 deficiency): Affects muscles, heart, and nerves, leading to weakness, weight loss, and cardiovascular issues.
    • Pellagra (B3 deficiency): Characterized by dermatitis, diarrhea, and dementia.
    • Megaloblastic Anemia (B12 deficiency): Causes fatigue, weakness, and nerve damage.
• Vitamin C (Ascorbic Acid):
  • Sources: Citrus fruits (oranges, lemons), berries, peppers, broccoli, tomatoes.
  • Functions: Acts as an antioxidant, protects cells from damage, essential for collagen production (for healthy skin, bones, and blood vessels), aids in wound healing, and enhances iron absorption.
  • Deficiency Diseases: Scurvy (leading to bleeding gums, fatigue, joint pain, poor wound healing), reduced immunity.
• Vitamin D (Calciferol):
  • Sources: Sunlight exposure (primary source), fatty fish (salmon, mackerel), fortified milk, egg yolks.
  • Functions: Helps the body absorb calcium and phosphate, crucial for strong bones and teeth. Also plays a role in immune function and muscle health.
  • Deficiency Diseases: Rickets (in children, causing soft and deformed bones), Osteomalacia (in adults, leading to weak bones and muscle pain), increased risk of osteoporosis.
• Vitamin E (Tocopherols):
  • Sources: Vegetable oils (sunflower, wheat germ), nuts, seeds, leafy green vegetables.
  • Functions: A powerful antioxidant that protects cells from damage by free radicals, supports immune function, and plays a role in blood clot prevention.
  • Deficiency Diseases: Rare, but can lead to neurological problems (nerve damage), muscle weakness, and impaired immune function.
• Vitamin K (Phylloquinone, Menaquinones):
  • Sources: Green leafy vegetables (kale, spinach, broccoli), some vegetable oils, fermented foods.
  • Functions: Essential for blood clotting (coagulation) and bone health.
  • Deficiency Diseases: Impaired blood clotting (leading to easy bruising and bleeding), weakened bones.

1.2.3 Water

• Functions:
  • Body Temperature Regulation: Helps regulate body temperature through perspiration.
  • Transportation: Acts as a solvent and transport medium for nutrients, oxygen, hormones, and waste products throughout the body.
  • Chemical Reactions: Serves as a medium for countless biochemical reactions in the body.
  • Lubrication and Cushioning: Lubricates joints, moistens tissues (eyes, mouth, nose), and acts as a shock absorber for organs and the brain.
  • Waste Excretion: Facilitates the removal of waste products through urine and feces.
  • Digestion and Absorption: Aids in the digestion of food and absorption of nutrients.
• Sources: Drinking water, beverages, fruits, and vegetables.

2. Role of Cellulose in Our Diet

• Meaning: Cellulose is a type of complex carbohydrate (polysaccharide) found in the cell walls of plants. Unlike other carbohydrates, humans lack the enzymes to digest cellulose.
• Importance (Dietary Fiber/Roughage):
  • Promotes Digestive Health: Although indigestible, cellulose acts as dietary fiber or roughage. It adds bulk to stool, which helps in regular bowel movements and prevents constipation.
  • Aids in Waste Elimination: It helps move food through the digestive tract, facilitating the elimination of waste products.
  • May Reduce Risk of Certain Diseases: A diet rich in fiber is associated with a reduced risk of diverticulosis, hemorrhoids, and some types of cancer.
  • Blood Sugar Control: Fiber can help slow down the absorption of sugar, contributing to better blood sugar control.
  • Satiety: Fiber-rich foods can promote a feeling of fullness, which can be beneficial for weight management.
• Sources: Whole grains, fruits (with skin), vegetables, legumes.

3. Balanced Diet

• Meaning: A balanced diet is a diet that provides all the essential nutrients (carbohydrates, fats, proteins, vitamins, minerals, and water) in the right proportions and adequate amounts to meet the body's needs for growth, maintenance, and optimal health. It ensures that the body receives sufficient energy and all necessary micronutrients without excess or deficiency.
• Importance:
  • Optimal Growth and Development: Especially crucial for children and adolescents.
  • Maintains Good Health: Supports all bodily functions, from immune response to cognitive function.
  • Prevents Deficiency Diseases: Ensures adequate intake of all vitamins and minerals, preventing conditions like scurvy, rickets, anemia, and goitre.
  • Boosts Immunity: A well-nourished body has a stronger immune system, making it more resistant to infections and diseases.
  • Provides Energy: Supplies the necessary energy for daily activities, physical work, and mental alertness.
  • Manages Weight: Helps maintain a healthy weight by providing satiety and preventing overeating of nutrient-poor foods.
  • Reduces Risk of Chronic Diseases: A balanced diet is a key factor in preventing chronic diseases such as heart disease, diabetes, obesity, and certain cancers.
  • Enhances Mental Well-being: Proper nutrition can positively impact mood, concentration, and overall mental health.

4. Malnutrition and Deficiency Diseases

Malnutrition refers to deficiencies, excesses, or imbalances in a person’s intake of energy and/or nutrients. It includes undernutrition (wasting, stunting, underweight), micronutrient deficiencies (lack of vitamins and minerals), overweight, and obesity.

4.1 Kwashiorkor

• Causes: Primarily caused by severe protein deficiency, often occurring in children who are weaned from breast milk onto a diet that is high in carbohydrates but very low in protein. It can also be triggered by infections that increase protein needs or reduce appetite.
• Symptoms:
  • Edema (swelling): Especially in the ankles, feet, and abdomen, due to fluid retention caused by a lack of proteins to maintain osmotic pressure.
  • Stunted Growth: Failure to grow and gain weight normally.
  • Muscle Wasting: Loss of muscle mass, though often masked by edema.
  • Changes in Skin and Hair: Skin lesions, flaky skin, depigmentation of hair (reddish or sparse hair), and easy hair pluckability.
  • Enlarged Liver: Due to fatty infiltration.
  • Apathy and Irritability: Behavioral changes.
  • Weakened Immune System: Increased susceptibility to infections.
• Prevention:
  • Adequate Protein Intake: Ensuring children receive sufficient protein in their diet, especially during and after weaning.
  • Breastfeeding: Promoting and supporting prolonged breastfeeding.
  • Diversified Diet: Introducing a variety of protein-rich foods (legumes, eggs, dairy, meat) into the diet.
  • Nutritional Education: Educating communities on proper feeding practices and the importance of protein.

4.2 Marasmus

• Causes: Caused by severe deficiency of all nutrients, including carbohydrates, fats, and proteins, leading to an overall energy and protein deficit. It typically results from prolonged starvation or insufficient intake of calories and protein.
• Symptoms:
  • Severe Wasting: Extreme loss of muscle and fat, giving the child a "skin and bones" appearance.
  • Stunted Growth: Significant impairment of growth and development.
  • Weight Loss: Drastic reduction in body weight.
  • Wrinkled Skin: Due to the loss of subcutaneous fat.
  • Old Man's Face: Sunken eyes and an aged appearance.
  • Weakness and Apathy: Extreme fatigue and lack of energy.
  • Chronic Diarrhea: Common due to impaired digestive function.
  • Weakened Immune System: Highly susceptible to infections.
• Prevention:
  • Adequate Calorie and Nutrient Intake: Ensuring a diet that provides sufficient energy and all essential nutrients.
  • Food Security: Addressing underlying causes of food scarcity and poverty.
  • Early Intervention: Identifying and treating children at risk of malnutrition.
  • Nutritional Support Programs: Implementing programs that provide supplementary feeding and nutritional education.

This expanded note provides a detailed and intuitive understanding of the topics covered in your syllabus, aiming to serve as a comprehensive study guide.