Nutrition and Food Science: A Comprehensive Guide to Nutrients

Posted on Aug 29, 2024 in Biology

Nutrition and Food Science

What is Nutrition?

Nutrition science is the study of foods and nutrients, and their actions, interactions, and balance in relation to health and disease. It also encompasses the social, economic, cultural, and psychological impacts of food. Nutrition can be viewed as an involuntary process that begins after food intake, providing energy, building and repairing body structures, and regulating metabolic processes.

What is Food?

Food comprises any substances that provide the body with the necessary raw materials to sustain life. It’s a voluntary, conscious, and educable process, influenced by cultural habits and economic factors.

Factors Influencing Food and Nutrition

  1. Improved living standards and food availability.
  2. Advancements in transportation, facilitating distribution.
  3. Development of food preservation techniques.
  4. Proliferation of synthetic and refined foods, potentially detrimental to health due to reduced natural food consumption (leading to issues like constipation).
  5. Advertising’s influence on consumer confusion and indiscriminate spending.
  6. Decline of traditional eating habits, often considered outdated and nutritionally inadequate.
  7. Sedentary lifestyles altering nutritional needs, requiring adjustments in food intake.

Food as a Source of Nutrients

Food is any substance taken from the external environment to be used in the synthesis of new living matter, as an energy source, and to regulate life processes.

Food provides two types of nutrients:

  • Nutrients the body cannot synthesize.
  • Nutrients the body can synthesize.

Common nutrients for most living organisms include:

  • Water
  • Carbohydrates
  • Lipids
  • Proteins
  • Vitamins
  • Minerals

Types of Nutrients

Organic/Biological: Found only in living organisms.

Inorganic: Water, minerals, and other elements necessary for metabolic reactions, also found in the surrounding physical environment.

Carbohydrates

Organic compounds formed by carbon, oxygen, and hydrogen. They play a vital role in nutrition, providing a sweet taste and serving as a primary energy source. In Western countries, they constitute 50% of total energy requirements.

Classification of Carbohydrates

Digestible Carbohydrates

1. Monosaccharides: Simple sugars, crystalline, sweet, colorless, and water-soluble. Examples include:

  • Glucose: The carbohydrate converted into energy for bodily functions.
  • Fructose: Found in fruits, vegetables, and honey.
  • Galactose: Rarely occurs freely in food.

2. Disaccharides: Composed of two monosaccharide units. Common examples:

  • Sucrose: Glucose + Fructose, found in fruits, vegetables, table sugar, and sweets.
  • Maltose: Glucose + Glucose, appears naturally and through starch hydrolysis.
  • Lactose: Glucose + Galactose, the milk disaccharide.

3. Polysaccharides: Contain multiple monosaccharide molecules. The most important is starch, found in cereals, legumes, and tubers.

Non-Digestible Carbohydrates

These polysaccharides are part of the plant cell wall and are not usable by the human body. Examples include:

  • Cellulose: Not digested, eliminated as stool, aids in stool formation and peristaltic movements.

Role of Carbohydrates

  • Energy: Primary fuel for cellular respiration.
  • Structure: Components of nucleic acids (DNA, RNA) and cell membranes.
  • Storage: Glycogen stores glucose for later use.

Daily Carbohydrate Needs

50-60% of daily calories should come from carbohydrates, with a minimum intake of 80-100 grams per day.

Lipids

Water-insoluble substances that dissolve in organic solvents (alcohol, ether). Composed of carbon, oxygen, and hydrogen, forming fatty acids. Lipids serve as an energy reserve, insulation, and protection for organs.

Classification of Lipids

  • Complex Lipids: Contain fatty acids, phosphoglycerides, sphingolipids, and waxes.
  • Simple Lipids: Steroids and prostaglandins.
  • Fatty Acids: Can be saturated (found in beef, lamb, milk) or unsaturated.
  • Essential Fatty Acids: Crucial for bodily functions, including linoleic acid (skin growth) and linolenic acid.

Based on their state at room temperature, lipids are classified as:

  • Fats: Solid at room temperature.
  • Oils: Liquid at room temperature.

Functions of Lipids

  • Energy: Concentrated energy source, releasing twice the energy of carbohydrates or proteins.
  • Storage: Primary energy reserve in the body.
  • Protection: Provide protective padding for organs.
  • Thermal Insulation: Prevent heat loss due to low thermal conductivity.
  • Structure: Components of cell membranes and nerve fiber sheaths.
  • Regulatory: Precursors to vitamins, hormones, and bile acids.
  • Carriers: Transport fat-soluble vitamins.

Daily Lipid Needs

30-35% of daily calories should come from fats, with a recommended intake of 60-80 grams per day.

Proteins

Macromolecules formed by carbon, hydrogen, oxygen, and nitrogen. They are composed of amino acids, linked together to form peptides and polypeptides. Proteins are essential for building and repairing body tissues.

Essential Amino Acids

These amino acids are crucial for life and cannot be synthesized by the body. There are 10 essential amino acids:

  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
  • Arginine
  • Histidine

Sources of Proteins

  • Animal Proteins: Meat, dairy products, fish, eggs, milk.
  • Plant Proteins: Vegetables, potatoes, fruits, legumes.

Properties of Proteins

  • Specificity: Each protein has a unique structure and function.
  • Denaturation: Loss of protein structure due to factors like heat.

Functions of Proteins

  • Structural: Building blocks of cells and tissues.
  • Energy: Used as fuel when carbohydrate and lipid reserves are depleted.
  • Enzymes: Facilitate chemical reactions in the body.
  • Transportation: Carry substances in the blood.
  • Storage: Some proteins, like casein in milk, provide amino acids for newborns.
  • Hormones: Examples include insulin and glucagon.
  • Cell Recognition: Glycoproteins on cell membranes allow cell identification.
  • Defensive: Immunoglobulins protect against foreign cells.

Daily Protein Needs

10-20% of daily calories should come from protein.

  • Men: 56 grams/day
  • Women: 44 grams/day

Protein needs may increase during pregnancy, adolescence, and childhood.