Nutrition Basics | Clinical Nutrition LAM Initiative

Nutrition Basics

Basic Components of a Healthy Diet

A healthy diet is typically composed of macronutrients, micronutrients, and fluids. When consumed in balance, it normally meets the body’s daily metabolic requirements.

Macronutrients

Macronutrients are substances needed for growth, metabolism, and other normal body functions. These nutrients are normally consumed in large quantities to provide bulk energy and building materials for the body.

Macronutrients are composed of:

  • Carbohydrates, organic compounds classified according to the number of saccharides, including monosaccharides, disaccharides and polysaccharides consist of carbon, hydrogen, oxygen and have numerous roles in living organisms, including energy production, as structural components and the backbone of RNA. Carbohydrates are needed for the central nervous system, heart, kidneys, and muscles to function properly. Approx. 45 to 65 percent of daily calorie intake should be in the form of carbohydrates.
  • Lipids serve a number of functions in the body, including being a dense source of energy storage, acting as structural components of cell membranes, supporting cellular development, helping with nerve cell transmission, protecting internal organs, providing insulation to retain body heat, and aiding in absorption of fat-soluble vitamins: A, D, K, E. Additionally, lipids serve as a mean for energy storage. Other lipids influence cellular signaling, can regulate gene expression, serve as a marker for cellular recognition or modulate lipid mediators. Fatty acids are the key constituent of lipids and are classified according to structural characteristics, including the length of the carbon chain, presence and position of double bonds in the chain, and their configuration (e.g. cis vs. trans). They may be classified as saturated (no double bond), unsaturated (one double bond), or poly-unsaturated (more than one double bond).
  • Proteins, composed of one or more chains of amino acids, are the primary source of nitrogen, provide essential nutrients for the body, and offer structural support including keratin for skin and hair, collagen for connective tissues, elastin, actin and myosin for muscles, and glycoproteins for cell membranes. Proteins also serve a functional role as enzymes; hormones for metabolic regulation; hemoglobin and transferrin for transport of oxygen and iron; albumin to regulate blood volume; and antibodies for the immune system. For example, Glutamine is involved in many metabolic processes. These include protein and glucose metabolism, serving as a carrier for nitrogen and carbon between organs, acting as a precursor for nucleotides, aiding cellular protection, and regulating acid base balance.

    Amino acids are divided into three types, including:
     
    • Essential Amino Acids which cannot be produced by the body and must be obtained through food
       
    • Conditional Amino Acids which cannot be produced by the body during special conditions such as illness.
       
    • Non-Essential Amino Acids which can be synthesized by the body

Micronutrients

Micronutrients are required for the maintenance of normal metabolism and antioxidant status. These nutrients are necessary for the efficient utilization of macronutrients.

Micronutrients include vitamins, minerals and trace elements:

  • Vitamins are categorized as water or lipid soluble. Water soluble vitamins require regular replacement in the body, while lipid soluble vitamins are stored in the liver and fatty tissues, and are eliminated more slowly:
    • Water soluble vitamins include vitamins B and C. B vitamins function in metabolism of carbohydrates, proteins, lipids and nucleic acids, thereby contributing to energy production, neurotransmission and the formation of red blood cells. Vitamin C acts as an antioxidant helping to protect cells from the damage caused by free radicals.
       
    • Lipid soluble vitamins include vitamin A, D, E and K. Vitamin A is an integral component for the rod and cone cells in the eye, and is essential for cell differentiation and reproduction, particularly during embryogenesis. D vitamins exhibit various functions, especially in the maintenance of calcium balance and bone health. Vitamin E is a potent antioxidant and free radical scavenger. Vitamin K is needed for proper functioning of the coagulation cascade.
  • Minerals include sodium, phosphorus, calcium, iron, potassium and magnesium. They are inorganic substances required for body processes. Minerals have many different functions such as fluid regulation, bone structure, muscle movement and nerve functioning.
  • Important trace elements required by the body include:
     
    • Iron assures that hemoglobin and myoglobin work properly to bind oxygen.
       
    • Zinc is a key micronutrient for metabolic pathways, stabilization of cell membranes, and immunofunction.
       
    • Selenium is involved in antioxidant protection and is important in thyroid hormone conversion.
       
    • Iodine is a constituent of the thyroid hormones, thereby influencing energy metabolism, cell growth processes and fetal development.

Water

Water is quantitatively the most important component of the human body, accounting for 50 to 60 percent of body weight, distributed in intra- and extracellular fluid compartments. The proper amount of water to a body allows body processes such as blood flow and the lymph system to function smoothly, making water a critical nutrient for health and survival.

Body processes where water is involved, include:

  • Fluid balance
  • Nerve impulses
  • Muscle contractions
  • Nutrient Transport
  • Removal of wastes
  • Chemical reactions

These are just a few of the roles water plays in the body. Water is a critical nutrient for health and survival.

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