Question
What is a balanced diet? List all the components of a balanced diet and explain why each is needed by the body. What happens when a component is deficient?
Solution — Step by Step
A balanced diet is one that contains all the essential nutrients — carbohydrates, proteins, fats, vitamins, minerals, water, and dietary fibre — in the right proportions for the body’s needs. The proportions vary based on age, gender, body weight, and activity level.
The concept of a balanced diet is important because no single food provides all nutrients. A variety of foods must be eaten regularly.
What they are: Compounds made of carbon, hydrogen, and oxygen. Include simple sugars (glucose, fructose, sucrose) and complex carbohydrates (starch, glycogen, dietary fibre).
Why needed: Primary fuel for all body cells. Brain cells depend almost exclusively on glucose. During exercise, muscles use glucose (and glycogen reserves) for ATP production.
Caloric value: 4 kcal/g.
Sources: Rice, wheat, maize, potatoes, bread, sugar.
Deficiency: Fatigue, weakness, weight loss (body breaks down protein and fat for energy).
Excess: Stored as glycogen (short term) and converted to fat (long term) → obesity.
What they are: Polymers of amino acids. There are 20 amino acids; 9 are essential (cannot be synthesised in the body — must come from diet).
Why needed: Building and repairing tissues, making enzymes, hormones, antibodies, and transport proteins (haemoglobin). Every chemical reaction in the body needs an enzyme — enzymes are proteins.
Caloric value: 4 kcal/g.
Sources: Eggs, meat, fish, milk, legumes (dal), soya beans.
Deficiency: Kwashiorkor (protein deficiency in young children — bloated belly, poor growth, skin lesions), marasmus (protein + calorie deficiency — muscle wasting, extreme thinness).
What they are: Triglycerides (glycerol + 3 fatty acid chains). Saturated (animal fats) and unsaturated (vegetable oils, fish).
Why needed:
- Concentrated energy store (9 kcal/g — more than double carbohydrates/proteins)
- Insulation (subcutaneous fat)
- Cell membrane structure (phospholipids)
- Absorb fat-soluble vitamins (A, D, E, K)
- Precursor for hormones (steroid hormones from cholesterol)
- Protect organs (visceral fat cushions kidneys, heart)
Sources: Butter, ghee, oil, nuts, seeds, fish.
Deficiency: Deficiency of essential fatty acids (omega-3, omega-6) causes skin problems, poor brain development, hormonal imbalance.
Vitamins: Organic compounds needed in tiny amounts for specific metabolic reactions. Fat-soluble (A, D, E, K — stored in body) and water-soluble (B-complex, C — not stored, need regular intake).
Key deficiencies: Vitamin C → scurvy (bleeding gums); Vitamin D → rickets (soft bones); Vitamin A → night blindness; Iron → anaemia.
Minerals: Inorganic elements needed for structural and metabolic functions. Calcium and phosphorus for bones/teeth. Iron for haemoglobin. Iodine for thyroid hormones. Sodium/potassium for nerve and muscle function.
Deficiencies: Calcium → osteoporosis; Iron → anaemia; Iodine → goitre (enlarged thyroid), cretinism in children.
Water: Makes up ~60% of body weight. Needed as solvent for all biochemical reactions, temperature regulation (sweating), transport (blood plasma, lymph), excretion. Dehydration causes headache, confusion, and in severe cases, death.
Dietary fibre (roughage): Indigestible plant cell wall material (cellulose, pectin). Does not provide nutrition directly but: stimulates intestinal motility, prevents constipation, reduces risk of colon cancer, slows glucose absorption.
Why This Works
No single macronutrient or micronutrient can substitute for another. The body has different biochemical needs that only specific nutrients fulfil. For example, nerve cell membranes require specific fatty acids; haemoglobin requires iron specifically (no other metal can substitute); certain enzyme cofactors require specific vitamins.
The “balanced” aspect refers to proportions: too much of any component is also harmful (excess carbohydrates cause obesity; excess fat-soluble vitamins cause toxicity; excess protein stresses kidneys). The right balance is what the body can use efficiently without waste or harm.
Alternative Method
A simplified classification for CBSE exams: nutrients are either:
- Energy-giving foods (carbohydrates, fats): provide calories for activity
- Body-building foods (proteins, minerals like calcium): growth and repair
- Protective foods (vitamins, minerals): prevent deficiency diseases and support immune function
- Roughage and water: regulate body functions
This three/four-way classification is the standard CBSE answer format.
Common Mistake
Students often say “fats are bad and should be avoided.” This is incorrect. Fats are essential — cell membranes are made of phospholipids (a type of fat), steroid hormones are derived from cholesterol, and fat-soluble vitamins cannot be absorbed without dietary fat. The problem is excess saturated fat and trans fat, not fat in general. A balanced diet includes a moderate amount of healthy fats (unsaturated fats from nuts, oils, fish).
In CBSE Class 6–7, deficiency diseases are a major exam topic. Build a quick table: Vitamin A → night blindness; Vitamin B₁ (thiamine) → beriberi; Vitamin C → scurvy; Vitamin D → rickets; Iron → anaemia; Iodine → goitre. These 6 deficiency diseases cover the vast majority of marks in this area.