Understanding Nutrients: Carbs, Fats, Proteins

Posted on Feb 26, 2025 in Human Nutrition and Dietetics

Complex Carbohydrates (Polysaccharides)

Large macromolecules made up of many monosaccharides. They are not sweet.

  • Glycogen: Found in animals, stored in the liver.
  • Starch: Found in plants, stored in leaves, roots, and tubers.
  • Cellulose: “Dietary Fiber” in plants, providing structural function.
  • Chitin: Forms the exoskeleton of invertebrates.

When broken down during digestion, glycogen and starch provide a steady and long-term supply of energy to the cell as simple sugars.

Simple Sugars

  • Are quickly metabolized to release energy.
  • Excess simple sugars are converted into fat!

Lipids

A diverse group of substances with a few common characteristics: water insolubility and an oily appearance.

Three Types of Lipids:

  • Fats: Rich in energy, can be saturated or unsaturated (triglycerides).
  • Membrane Lipids: Make up cell membranes (phospholipids, cholesterol).
  • Regulatory Lipids: Control metabolic processes (vitamins A, D, K, E, and hormones).

Saturated Fats

Primarily of animal origin, solid at room temperature. Contribute to increased levels of “bad cholesterol” (LDL). Excess is a risk factor for cardiac disease and stroke.

Unsaturated Fats

Primarily of plant origin (but sometimes animal), liquid at room temperature (oils), and easily digestible. Help prevent LDL levels from rising.

“Trans” Fats (Hydrogenated)

Artificially saturated plant fats with hydrogen to create solid, durable, and tastier foods. Pose a serious risk of increasing LDL cholesterol levels.

Proteins

Proteins make up half of our dry body weight. They are the most important structure-building molecules in our body (bones, cartilage, connective tissue, muscles, etc.). Proteins are macromolecules made by joining numerous smaller molecules called amino acids.

Proteins and Amino Acids

Proteins are composed of a chain of amino acids (called a peptide) with a specific 3D structure that determines the protein’s function.

Protein Functions and Types

  • Forming body structures (bones, teeth, cartilages, ligaments): Collagen, Keratin.
  • Oxygen transport in blood: Hemoglobin.
  • Lipid transport in blood: Lipoproteins (LDL, HDL).
  • Defense and immunity: Antibodies.
  • Muscle/Cardiac contraction: Actin & Myosin.

Mineral Salts

They are essentially regulators of our vital functions, but some form bones and teeth. Fruits, vegetables, and dried fruits are rich in salts. The lack of certain salts like Iron (Fe), Calcium (Ca), or Iodine (I) can cause serious illnesses and deficiencies (anemia, hypothyroidism).

A Healthy Diet

A healthy and balanced diet prevents many disorders and deficiencies associated with nutrition: overweight, obesity, malnutrition, deficiencies, etc. It must contain all nutrients in adequate amounts. It should provide the adequate daily energy needs, according to our age, sex, weight, and physical activity.

  • Carbohydrates: 55%
  • Fats: 30%
  • Proteins: 15%

The Food Wheel

Divides foods into five major groups based on nutrient content and their function in our body:

  1. Fruits and vegetables (regulatory, fiber, vitamins).
  2. Starchy foods (energetic, carbohydrates).
  3. Oils, spreads (energetic, fats).
  4. Dairy products (energetic, structural; proteins, fats).
  5. Meat, pulses, eggs, poultry (structural, proteins).

Approximately 3/4 of our daily diet should be based on groups 1 and 2. Consider incorporating more plant-based meals into your diet.