Nutrients are essential substances required by the human body for growth, maintenance, repair, reproduction, immunity, and overall well-being. While energy is a primary nutritional requirement, many other nutrients are equally important because they perform vital physiological, structural, metabolic, and protective functions. These nutrients are broadly classified into proteins, fats, vitamins, minerals, water, and dietary fibre. Adequate intake of these nutrients is essential for achieving optimal nutritional status, preventing deficiency diseases, promoting healthy growth and development, and reducing the risk of chronic illnesses. Community nutrition programmes focus not only on providing sufficient calories but also on ensuring the adequate intake of all essential nutrients throughout the life cycle. Proteins are among the most important nutrients after energy. They are composed of amino acids, which serve as the building blocks of the body. Proteins are required for the growth and repair of tissues, synthesis of enzymes and hormones, formation of antibodies, maintenance of fluid balance, and transport of various substances in the blood. During infancy, childhood, adolescence, pregnancy, and lactation, the demand for protein increases because of rapid tissue growth and development. Protein deficiency may lead to growth retardation, muscle wasting, lowered immunity, delayed wound healing, and severe forms of protein-energy malnutrition such as kwashiorkor and marasmus. Proteins are classified as complete and incomplete proteins depending on their amino acid composition. Animal foods such as milk, eggs, fish, poultry, and meat provide complete proteins containing all essential amino acids. Plant proteins found in cereals, pulses, legumes, nuts, and seeds are generally incomplete but can provide high-quality protein when consumed in appropriate combinations. The traditional Indian practice of combining cereals with pulses, such as rice with dal or chapati with lentils, improves the biological value of dietary protein. Fats are another essential nutrient that performs several important functions beyond supplying energy. Fats provide essential fatty acids, support the absorption of fat-soluble vitamins, protect vital organs, maintain body temperature, and contribute to cell membrane structure. They are involved in hormone production, brain development, and nervous system functioning. Adequate dietary fat is particularly important during infancy and early childhood when rapid brain growth occurs. Essential fatty acids such as linoleic acid and alpha-linolenic acid cannot be synthesized by the human body and must be obtained from food. Vegetable oils, nuts, seeds, soybeans, fish, and certain animal products are good sources of essential fatty acids. Omega-3 fatty acids found in fatty fish, flaxseed, walnuts, and chia seeds support cardiovascular health, cognitive development, and reduce inflammation. Omega-6 fatty acids also play important roles in growth and immune function. Excessive intake of saturated fats and trans fats, however, increases the risk of obesity, cardiovascular disease, diabetes, and other non-communicable diseases. Community nutrition programmes encourage the use of unsaturated vegetable oils and limit the consumption of unhealthy fats. Vitamins are organic compounds required in small quantities for regulating numerous metabolic processes. Although needed in minute amounts, vitamin deficiencies can result in serious health problems. Vitamins are classified into fat-soluble vitamins and water-soluble vitamins. Vitamin A is essential for normal vision, healthy skin, immune function, and cell growth. It helps maintain the integrity of epithelial tissues and reduces susceptibility to infections. Vitamin A deficiency is a major public health problem in many developing countries, particularly among preschool children and pregnant women. It may cause night blindness, xerophthalmia, corneal ulceration, and irreversible blindness. Children with vitamin A deficiency are also more vulnerable to respiratory infections, diarrhoea, and measles. Rich dietary sources include liver, egg yolk, milk, butter, green leafy vegetables, carrots, pumpkin, papaya, and mango. Community nutrition programmes often include vitamin A supplementation for children to prevent deficiency. Vitamin D plays an essential role in calcium and phosphorus metabolism, promoting healthy bones and teeth. It facilitates calcium absorption from the intestine and supports normal bone mineralization. Deficiency leads to rickets in children and osteomalacia in adults. Elderly individuals may develop osteoporosis due to prolonged deficiency. The body synthesizes vitamin D when the skin is exposed to sunlight. Food sources include fortified milk, eggs, fish liver oil, fatty fish, and fortified cereals. Adequate sunlight exposure remains one of the simplest and most effective preventive measures. Vitamin E functions primarily as an antioxidant, protecting body cells from damage caused by free radicals. It contributes to immune function, reproductive health, and maintenance of healthy skin and muscles. Vegetable oils, nuts, seeds, wheat germ, and green leafy vegetables are important dietary sources. Although deficiency is uncommon, inadequate intake may contribute to neuromuscular disorders and impaired immune response. Vitamin K is essential for normal blood clotting and bone metabolism. It helps synthesize clotting factors that prevent excessive bleeding following injury. Green leafy vegetables, cabbage, broccoli, soybean oil, and intestinal bacteria contribute to vitamin K supply. Deficiency may result in bleeding disorders, particularly in newborn infants who are routinely administered vitamin K shortly after birth. The B-complex vitamins consist of several water-soluble vitamins that participate in energy metabolism, nervous system function, red blood cell formation, and DNA synthesis. Thiamine (Vitamin B1) is necessary for carbohydrate metabolism and normal nerve function. Deficiency causes beriberi, characterized by muscle weakness, nerve damage, and cardiac abnormalities. Whole grains, pulses, nuts, pork, and fortified cereals are good sources. Riboflavin (Vitamin B2) is involved in energy production and maintenance of healthy skin, eyes, and mucous membranes. Deficiency causes cheilosis, angular stomatitis, glossitis, and eye irritation. Milk, eggs, green vegetables, and whole grains