A person feeds on rice and vegetable made up of potato only. He is likely to suffer from deficiency of:

1. Introduction to Macronutrients: Carbohydrates, Proteins, and Fats (basic)

To understand human health, we must first look at macronutrients—the essential compounds our bodies require in large quantities to function, grow, and maintain themselves. Think of macronutrients as the primary fuel and raw materials for your body's engine. These are generally classified into three main groups: Carbohydrates, Proteins, and Fats. While all food provides some form of energy, different nutrients serve distinct biological purposes. For instance, some nutrients are broken down to release energy via respiration, while others are used to build and repair the body Science-Class VII, Life Processes in Animals, p.128.

Carbohydrates are the body’s preferred energy source. In the Indian context, these are often found in staple grains like rice, wheat, barley, and millets (such as bajra, jowar, and ragi), as well as tubers like potatoes Exploring Society: India and Beyond. Social Science-Class VI, Unity in Diversity, or 'Many in the One', p.127. These foods are rich in starch, a complex carbohydrate. While they are excellent for providing the fuel needed for daily activities, a diet consisting strictly of starchy staples lacks the diversity required for holistic health. Reliance on a single type of food, like just rice or potatoes, can lead to specific nutritional gaps because these items are relatively low in the "building blocks" of life.

Proteins and Fats round out the macronutrient trio. Proteins are vital for the growth of new tissues and the repair of damaged ones. Common Indian sources include various pulses (dals), milk, and meat products Exploring Society: India and Beyond. Social Science-Class VI, Unity in Diversity, or 'Many in the One', p.127. Fats, on the other hand, act as concentrated energy reserves and are essential for absorbing certain vitamins and protecting organs. Achieving a healthy body requires a balance of these three; as we see in nature, organisms must consume a variety of sources to maintain harmony within their biological systems Science, Class VIII, How Nature Works in Harmony, p.207.

Sources: Science-Class VII, Life Processes in Animals, p.128; Exploring Society: India and Beyond. Social Science-Class VI, Unity in Diversity, or 'Many in the One', p.127; Science, Class VIII, How Nature Works in Harmony, p.207

2. Role of Carbohydrates and Starchy Staples (basic)

Carbohydrates are the body's primary source of energy, often referred to as the "biological fuel" that powers our daily activities. In the context of human nutrition, we frequently encounter starchy staples—foods that are eaten regularly and in such quantities that they constitute a dominant portion of a standard diet. Common examples include rice, potatoes, tapioca, and sweet potatoes Environment, Shankar IAS Academy, Agriculture, p.353. Among these, the potato is particularly significant in global food security because it yields far more starch than many cereal crops and can thrive in a variety of climatic conditions Physical Geography, PMF IAS, Chapter 30, p.459.

From a scientific perspective, starch is a complex carbohydrate that we can easily identify using a simple chemical indicator. When a dilute iodine solution is added to a food item containing starch, it reacts to produce a characteristic blue-black color Science-Class VII, NCERT, Chapter 9, p.124. This reaction is a fundamental tool in nutritional science to confirm the presence of energy-dense carbohydrates. Interestingly, our bodies begin processing these starches the moment we eat; saliva contains enzymes that start breaking down complex starch into simpler sugars. This is why chewed rice shows a much weaker reaction to iodine than plain boiled rice—the starch is already being transformed Science-Class X, NCERT, Life Processes, p.85.

However, an important concept in UPSC preparation is understanding the limitations of a single-source diet. While starchy staples are excellent for providing energy and some vitamins (like Vitamin B and C), they are critically low in protein. A 100g serving of rice or potato typically provides only about 2.5g to 2.7g of protein. Because proteins are essential for the growth and repair of body tissues, a diet that lacks diversity—relying solely on starches without including pulses, milk, or meat—can lead to Protein-Energy Malnutrition (PEM).

Sources: Environment, Shankar IAS Academy, Agriculture, p.353; Physical Geography, PMF IAS, Chapter 30, p.459; Science-Class VII, NCERT, Chapter 9, p.124; Science-Class X, NCERT, Life Processes, p.85

3. Proteins: The Building Blocks of Life (intermediate)

Proteins are often described as the building blocks of life, but their role is far more dynamic than just providing structure. Chemically, proteins are complex organic molecules made up of smaller units called amino acids. While carbohydrates and fats are primarily composed of Carbon, Hydrogen, and Oxygen, proteins are distinguished by the presence of Nitrogen, which constitutes nearly 16% of their weight Environment, Shankar IAS Academy, Functions of an Ecosystem, p.19. Certain essential amino acids also incorporate Sulfur, making Nitrogen and Sulfur vital for protein synthesis in both plants and animals Environment, Shankar IAS Academy, Agriculture, p.363.

In the biological hierarchy, proteins serve as the bridge between our genetic code and our physical traits. Cellular DNA acts as the information source, where a specific segment known as a gene provides the instructions to build a particular protein Science, class X (NCERT 2025 ed.), Heredity, p.131. These proteins then go on to perform critical functions:

• Enzymes: They act as biological catalysts, enabling chemical reactions like digestion and metabolism to occur at life-sustaining speeds.
• Hormones: They regulate physiological processes; for example, growth hormones determine the height of a plant or the development of a human Science, class X (NCERT 2025 ed.), Heredity, p.131.
• Tissue Repair: They are essential for the growth and maintenance of muscles, skin, and organs.

From a nutritional perspective, pulses (legumes) are the primary source of protein in the Indian vegetarian diet Environment, Shankar IAS Academy, Agriculture, p.353. Unlike many other crops, legumes have a symbiotic relationship with bacteria that allows them to perform nitrogen fixation, converting atmospheric nitrogen into the building blocks necessary to produce protein-rich seeds INDIA PEOPLE AND ECONOMY, Geography Class XII, Land Resources and Agriculture, p.28. This is why a diet dominated by starchy foods like rice and potatoes, while high in energy, often lacks the necessary nitrogenous compounds to support long-term tissue repair and growth.

Nutrient Type	Primary Elements	Main Function
Carbohydrates	C, H, O	Immediate Energy (Fuel)
Proteins	C, H, O, N, (S)	Growth, Repair, Enzymes, and Hormones

Sources: Environment, Shankar IAS Academy, Functions of an Ecosystem, p.19; Environment, Shankar IAS Academy, Agriculture, p.363; Science, class X (NCERT 2025 ed.), Heredity, p.131; Environment, Shankar IAS Academy, Agriculture, p.353; INDIA PEOPLE AND ECONOMY, Geography Class XII, Land Resources and Agriculture, p.28

4. Protein-Energy Malnutrition (PEM) and Health Impacts (intermediate)

Protein-Energy Malnutrition (PEM) is a critical health condition that occurs when the body does not receive enough proteins, calories (energy), or both. While carbohydrates like rice and potatoes are excellent sources of starch and provide the energy required for daily activities, they are insufficient for the body's structural needs. Proteins are the 'building blocks' of life; they are indispensable for tissue repair, muscle growth, and the formation of blood Science-Class VII, NCERT(Revised ed 2025), Adolescence: A Stage of Growth and Change, p.79. A diet heavily dominated by starchy foods without diverse inclusions like pulses, milk, or meat often leads to a specific protein deficiency, even if the person's caloric intake seems adequate.

The impact of PEM is most visible during periods of rapid development, such as adolescence. Without adequate protein, the body cannot achieve optimal bone strength or proper physical growth Science-Class VII, NCERT(Revised ed 2025), Adolescence: A Stage of Growth and Change, p.79. In the Indian context, pulses (like Red gram, Black gram, and Soyabean) serve as the most economical and primary source of essential amino acids to combat this deficiency Environment, Shankar IAS Academy (ed 10th), Agriculture, p.353. When a diet lacks these protein-rich components, the individual may fall into the 'malnourished' category, often identified as being underweight for their age Understanding Economic Development, Class X, NCERT(Revised ed 2025), CONSUMER RIGHTS, p.89.

To better understand the nutritional landscape, we can compare the roles of the two primary macronutrients involved in PEM:

Nutrient	Primary Role	Common Sources	Deficiency Impact
Carbohydrates	Immediate Energy (Fuel)	Rice, Potatoes, Wheat	Lethargy, Weight loss
Proteins	Growth & Tissue Repair	Pulses, Milk, Eggs, Meat	Stunted growth, Weak immunity

Sources: Science-Class VII . NCERT(Revised ed 2025), Adolescence: A Stage of Growth and Change, p.79; Environment, Shankar IAS Academy (ed 10th), Agriculture, p.353; Understanding Economic Development. Class X . NCERT(Revised ed 2025), CONSUMER RIGHTS, p.89

5. Micronutrients: Vitamins and Minerals (intermediate)

In our journey through human nutrition, we move from the 'macro' building blocks to the micronutrients—vitamins and minerals. While needed in minute quantities compared to carbohydrates or proteins, they act as the essential 'spark plugs' for our metabolic engine. Vitamins are organic compounds that primarily assist in biochemical reactions. A critical way to understand them is through their solubility. Vitamins like A, D, E, and K are fat-soluble, meaning they can be stored in the body's adipose tissue and liver. In contrast, water-soluble vitamins (like Vitamin C and the B-complex group) are not stored extensively; if consumed in excess, they are typically excreted by the body via urine Environment, Shankar IAS Academy (ed 10th), Functions of an Ecosystem, p.16. This distinction is vital: while we need a daily supply of water-soluble vitamins, fat-soluble ones can accumulate, sometimes reaching toxic levels if taken in extreme excess.

Minerals, on the other hand, are inorganic elements that the body needs for structural purposes and regulatory functions. For instance, Iodine is a trace mineral absolutely essential for the thyroid gland to synthesize the hormone thyroxin. Thyroxin regulates the metabolism of carbohydrates, proteins, and fats to provide the best balance for growth. When iodine is deficient in our diet, the thyroid gland struggles to produce enough hormone, often leading to goitre, characterized by a noticeably swollen neck Science, class X (NCERT 2025 ed.), Control and Coordination, p.110. Similarly, minerals like Iron are central to hemoglobin, while Calcium and Phosphorus build our skeletal framework.

When our diet lacks these specific micronutrients over a long period, we develop deficiency diseases. Unlike infections caused by germs, these are non-communicable and often chronic, meaning they persist for a long time if the nutritional gap isn't bridged Science, Class VIII, NCERT (Revised ed 2025), Health: The Ultimate Treasure, p.36. For a student of the UPSC, it is important to realize that health isn't just the absence of disease, but a delicate hormonal and chemical balance maintained by these tiny but mighty nutrients.

Type	Storage in Body	Examples	Key Function/Risk
Fat-Soluble	Stored in liver/fat tissues	A, D, E, K	Can accumulate; potential for toxicity.
Water-Soluble	Generally not stored (excreted)	B-complex, C	Require regular daily intake; low toxicity risk.

Sources: Environment, Shankar IAS Academy (ed 10th), Functions of an Ecosystem, p.16; Science, class X (NCERT 2025 ed.), Control and Coordination, p.110; Science, Class VIII, NCERT (Revised ed 2025), Health: The Ultimate Treasure, p.36

6. Dietary Diversification and Balanced Nutrition (exam-level)

In our journey toward mastering human health, we must understand that dietary diversification is the cornerstone of sustainable nutrition. It is the practice of consuming a wide variety of foods across different food groups to ensure the body receives all necessary macro and micronutrients. While a diet centered on staples like rice and potatoes provides ample carbohydrates for energy—identifiable by the classic blue-black reaction in iodine tests—relying on them exclusively creates a dangerous nutritional gap. These starchy foods are remarkably low in proteins, providing only about 2.5g to 2.7g per 100g serving. Without diverse sources like pulses, milk, or meat, the body cannot perform essential tissue repair and growth, leading to Protein-Energy Malnutrition (PEM).

Historically, the Indian diet has shown a preference for variety, often incorporating milk, ghee, and grains, though regional and cultural practices dictated specific inclusions or exclusions History , class XI (Tamilnadu state board 2024 ed.), Harsha and Rise of Regional Kingdoms, p.110. In the modern context, we distinguish between chronic hunger and seasonal hunger. Chronic hunger isn't just about an empty stomach; it is often a consequence of diets that are persistently inadequate in terms of quality Economics, Class IX . NCERT(Revised ed 2025), Food Security in India, p.45. A person might consume enough calories to survive but remain malnourished because their diet lacks the micronutrients and proteins found in a diversified meal plan.

From a governance perspective, the importance of nutrition is so vital that it is embedded in our Directive Principles of State Policy (DPSP). Under Article 47, the State is tasked with the duty to raise the level of nutrition and the standard of living of its people. Although these principles are non-justiciable—meaning they cannot be enforced by a court—they carry a moral and political force that guides the government in implementing food security programs aimed at eliminating both quantity-based and quality-based hunger Indian Constitution at Work, Political Science Class XI (NCERT 2025 ed.), RIGHTS IN THE INDIAN CONSTITUTION, p.43.

Nutritional Aspect	Staple-Only Diet (e.g., Rice/Potato)	Diversified Diet
Primary Component	High Starch/Carbohydrates	Balanced Macros (Protein, Fats, Carbs)
Health Outcome	Risk of Protein-Energy Malnutrition	Optimal Growth and Tissue Repair
Hunger Type	May satisfy hunger but remains "Hidden Hunger"	Addresses both Quantity and Quality

Sources: History , class XI (Tamilnadu state board 2024 ed.), Harsha and Rise of Regional Kingdoms, p.110; Economics, Class IX . NCERT(Revised ed 2025), Food Security in India, p.45; Indian Constitution at Work, Political Science Class XI (NCERT 2025 ed.), RIGHTS IN THE INDIAN CONSTITUTION, p.43

7. Solving the Original PYQ (exam-level)

Now that you have mastered the fundamental categories of macronutrients, this question tests your ability to apply that knowledge to real-world dietary scenarios. You've learned that carbohydrates are the primary energy source, while proteins are the essential building blocks for tissue repair and growth. When you look at a diet consisting purely of rice and potatoes, you must identify their primary nutrient profile. According to Science-Class VII . NCERT(Revised ed 2025), both items are rich in starch (a complex carbohydrate). While they provide quick energy, they are critically low in the nitrogen-based compounds required for body-building.

To arrive at the correct answer, evaluate what is missing from the plate. A balanced diet requires a mix of energy-giving foods and body-building foods. Since the person is consuming ample rice and potatoes, they are getting plenty of carbohydrates, meaning options (A) and (C) are logically impossible—you cannot suffer a deficiency of something you are consuming in abundance. Between (B) and (D), while the diet may be low in fats, the absence of pulses, milk, or meat—the primary sources of proteins—is the most significant clinical concern. As noted in Physical Geography by PMF IAS, potatoes yield high starch but very little protein, making (B) Proteins the most accurate choice for a likely deficiency.

The UPSC often uses common traps by including "Carbohydrate" in the distractors. Students often see "rice" and immediately think "Carbohydrates," leading them to pick (A) or (C) without reading the word "deficiency" carefully. Always remember: a deficiency occurs in what you lack, not what you eat. By eliminating any option containing carbohydrates, you are left with the realization that this person is missing the essential components for structural growth, resulting in protein-energy malnutrition if the diet persists.