The bare essentials for a human diet consist of six fundamental classes of nutrients: water, carbohydrates, fats (lipids), proteins, vitamins, and minerals.
Water is critical, with a minimum requirement estimated at about 1 liter per day under ideal conditions.
Carbohydrates are not strictly essential, as the body can synthesize them from protein and fat through gluconeogenesis, meaning a human can survive without dietary carbohydrates.
The essential macronutrients are proteins and fats, which provide structural materials and energy. Proteins are required for tissue building and repair, and the body needs nine essential amino acids that cannot be synthesized internally.
Fats are essential for energy, cell structure, and the absorption of fat-soluble vitamins, requiring two essential fatty acids: alpha-linolenic acid (omega-3) and linoleic acid (omega-6).
Micronutrients, including thirteen essential vitamins (such as A, C, D, E, K, and the B-complex) and various minerals (like calcium, iron, zinc, and potassium), are vital for regulating metabolic processes and preventing deficiency diseases.
While the exact minimum daily intake for survival for most nutrients is not precisely known due to ethical limitations in research, meeting the requirements for these essential nutrients is fundamental for sustaining life.