The Fundamentals of Nutrition: A Comprehensive Guide

Posted on May 14, 2024 in Biology

Nutrition: A Comprehensive Guide

Introduction

Alimentation: The process of selecting and consuming food from the environment, forming voluntary dietary habits. It is influenced by many factors.

Nutrition: The set of processes by which our body incorporates nutrients from food and transforms them. Food and nutrition satisfy our needs for energy and essential nutrients.

Nutrients: Simple molecules obtained from food that the body uses for metabolic reactions.

Food: Any natural product or substance that can be consumed or transformed to provide the body with the nutrients needed to meet its needs and sustain life.

Food Groups

The food groups are a way of classifying foods based on their nutrient content. They are:

  1. Milk and its derivatives: Rich in protein, which is essential for growth and repair. Contributes 15% of daily calories and provides 4kcal/g.
  2. Meat, fish, eggs: Also rich in protein, contributing 15% of daily calories and providing 4kcal/g.
  3. Cereals, pulses, and tubers: Primary source of carbohydrates, providing 55-60% of daily energy. They provide 4kcal/g.
  4. Vegetables, fruits, and vegetables: Excellent sources of carbohydrates, vitamins, and minerals. Essential for overall health and well-being.
  5. Fatty foods: Provide lipids, which are a concentrated source of energy, contributing 30% of daily calories and providing 9kcal/g.

Dairy Products

Dairy products like yogurt, cheese, and kefir are rich in protein, carbohydrates, fats, and vitamins A and D.

  • Yogurt and Kefir: Obtained by fermenting milk with saprophytic germs (starter cultures).
  • Dairy Desserts: Obtained from the fermentation of milk that has been sterilized by heating.
  • Cheese: Derived from milk and aged for months. Contains little lactose (except cottage cheese) and water. Rich in calcium, with 300 to 800 mg per 100g, depending on the variety and curing process.
  • Butter: Contains 20% water and the rest is milk fat. Provides 720kcal per 100g and is rich in vitamins A, D, and E. High in fat and cholesterol (250mg per 100g), with almost no calcium, protein, or B vitamins.
  • Cream or Cream Milk: Contains less water and more fat than whole milk, resulting in lower protein and lactose content.

Methods of Milk Presentation, Handling, and Conservation

  • Raw Milk: Milk directly from the cow. Should not be consumed directly and must be boiled for 5 minutes to kill germs. Store in the refrigerator and consume within a short time.
  • Pasteurized Milk: Commercially available milk that has been heated to 70°C for a few seconds. Consume within 3 days and store in the refrigerator.
  • Sterilized Milk: The most common type, heated to 133°C or 170°C (UHT system). Eliminates germs and spores, allowing for preservation for up to 4 months.
  • Whole Milk: Has not undergone any treatment to alter the amount of fat.
  • Skim Milk: Has had three-quarters of its fats and cholesterol removed, along with almost all fat-soluble vitamins A and D. Lower in calories and cholesterol but also less flavorful.
  • Semi-skimmed Milk: A compromise between whole and skim milk, offering a balance of advantages and disadvantages.
  • Fortified Milk and Vitamins: Milk that has been enriched with certain substances to improve its nutritional properties.

Redundant Foods

Redundant foods are not necessary from a nutritional point of view and include jam, table sugar, chocolates, cakes, soft drinks, and alcoholic beverages.

Protein Foods

Protein foods include milk, eggs, meat, and fish. Legumes and cereals also contain protein.

Cereals

Cereals like rice, wheat, corn, and barley provide significant amounts of carbohydrates and starch. Whole grains are also good sources of fiber and vitamins.

Legumes

Legumes such as chickpeas, beans, lentils, and peas are good sources of carbohydrates, starch, protein, and fiber. Their protein content is comparable to that of meat, making them an economical protein source.

Tubers

Tubers like potatoes, sweet potatoes, turnips, parsnips, and carrots are rich in vitamins, potassium, and carbohydrates.

Nuts

Nuts such as almonds, peanuts, hazelnuts, walnuts, and pistachios are high in fat and protein, with a moderate amount of carbohydrates.

Vegetables and Fruits

Vegetables and fruits are rich in fiber, vitamins, and minerals.

  • Vegetables: Chard, spinach, cabbage, tomatoes, cucumbers, peppers.
  • Fruit: Apples, oranges, bananas, berries. Rich in vitamins, minerals, carbohydrates, sugars, and fiber.

Fats, Oils, and Butter

Fats, oils, and butter are solid at room temperature and are derived from animals.

Classification of Nutrients

Macronutrients

Macronutrients are nutrients that the body needs in large amounts. They include:

  • Carbohydrates: Provide energy.
  • Lipids: Provide energy and are essential for various bodily functions.
  • Proteins: Essential for growth, repair, and regulation of bodily processes.

Micronutrients

Micronutrients are nutrients that the body needs in small amounts. They include:

  • Vitamins: Regulate metabolic reactions and support various bodily functions.
  • Minerals: Essential for various bodily functions, including bone health, nerve function, and fluid balance.

Other Classifications

  • Organic nutrients: Carbohydrates, lipids, proteins, vitamins.
  • Inorganic nutrients: Minerals and salts.

Nutrients and Metabolism

Nutrients are organic and inorganic substances used by the body in its metabolism.

Metabolism is the set of chemical reactions taking place in different cells of living beings, from which they obtain energy and synthesize substances needed to ensure the proper functioning of the body.

Water

Water is an essential nutrient, although it does not provide any calories. It is the single most important molecule for living organisms, as we are composed of about 60% water. Water serves several functions:

  • Shock absorption, pressure regulation, and lubrication of joints.
  • Solvent for various substances.
  • Facilitates diffusion of molecules and chemical reactions.
  • Involved in many metabolic reactions.

We lose about two gallons of water each day under normal conditions. Water loss is replenished by drinking water or other fluids. Therefore, we only need to drink about 1.5 liters of fluid each day.

Carbohydrates

Carbohydrates (sugars) are molecules primarily made up of carbon, hydrogen, and oxygen. They are the body’s primary source of energy.

Monosaccharides

Monosaccharides are simple sugars that provide quick energy. They include:

  • Glucose: The most abundant monosaccharide in our body. It is not essential, as the body can produce it from other carbohydrates.
  • Fructose: The sweetest monosaccharide, found in fruits and honey. The body converts it into glucose.
  • Galactose: A monosaccharide found in milk. It is usually combined with glucose to form lactose.

Disaccharides

Disaccharides are formed by the joining of two monosaccharides. The most common in the diet are:

  • Lactose: The natural sugar in milk, formed by the combination of glucose and galactose.
  • Sucrose: The natural sugar in fruits, formed by the combination of glucose and fructose.
  • Maltose: Found in cereals, formed by the combination of two glucose molecules.

Polysaccharides

Polysaccharides are complex carbohydrates composed of long chains of monosaccharides. They do not have a sweet taste. The most common are:

  • Glycogen: A molecule used as a store of glucose in the liver and muscles. It is the animal equivalent of starch.
  • Starch: The storage form of glucose in plants, found in cereals, legumes, and tubers. It is the energy reserve of plants.
  • Cellulose: Forms the plant cell wall (skeleton). Intestinal enzymes cannot break down cellulose, which is why it is considered fiber. We need 25-40g of fiber per day, obtained from fruits and vegetables.

Proteins

Proteins make up 15% of daily calories and are macromolecules consisting of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sometimes other elements such as sulfur (S) and phosphorus (P). Proteins are formed by amino acids (20 different types).

Amino Acids

Amino acids are the building blocks of proteins. Essential amino acids are those that the body cannot manufacture and must be obtained from food. The essential amino acids are:

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

In children, histidine is also considered an essential amino acid.

Non-essential amino acids are those that the body can synthesize.

Complete proteins or proteins of high biological value contain all the essential amino acids. Proteins can complement each other, such as the combination of legumes and cereals.

The recommended daily intake of protein for adults is 0.8g per kilogram of body weight.

Protein Differences in Structure

Proteins can be classified as soluble or insoluble in water, and they can have a globular or fibrous structure.

  • Globular proteins: Found in body fluids and involved in metabolism, such as hormones and enzymes. Casein in milk is a globular protein. Some proteins bind to non-protein substances, forming glycoproteins, lipoproteins, and phosphoproteins.
  • Fibrous proteins: Insoluble in water and have high mechanical strength. They are part of the body’s structure, such as keratin, collagen, and connective tissue. Each species of animal or plant has its own unique set of proteins.

Lipids

Lipids are molecules with many different structures and functions. The common characteristic of all lipids is that they are insoluble in water.

Simple Lipids

Simple lipids are composed of fatty acids, which are chains of carbon, hydrogen, and oxygen. Fatty acids can be saturated or unsaturated.

  • Saturated fatty acids: Solid at room temperature and commonly called”fats” They promote the development of atherosclerosis, a condition in which fats harden in the arteries, increasing the risk of heart attack. Examples include palm oil and coconut oil.
  • Unsaturated fatty acids: Liquid at room temperature and found in plant foods such as oils and fatty fish. They help prevent atherosclerosis. Examples include olive oil (monounsaturated) and nuts and avocado (polyunsaturated).

Essential Fatty Acids

Essential fatty acids are those that the body cannot produce and must be obtained from food. They include:

  • Omega-6 linoleic acid: Found in olive oil and oily fish.
  • Omega-3 alpha-linolenic acid: May offer protection against some tumors, such as breast, colon, and prostate cancer. Found in nuts and soybean oil.

Unsaturated fatty acids should make up 25% of the lipid intake. They help prevent water loss through the skin, contribute to the smooth functioning of the cardiovascular system, and decrease blood triglyceride levels.

Vitamins

Vitamins are a group of essential molecules that we consume in the diet. They collaborate in metabolic reactions, facilitating the action of enzymes. Lack of vitamins can cause disease.

Lipid-Soluble Vitamins

Lipid-soluble vitamins dissolve in fat but not in water. They are present in many fatty foods, but excessive consumption can be harmful. They include:

  • Vitamin A (retinol)
  • Vitamin D
  • Vitamin E
  • Vitamin K

Water-Soluble Vitamins

Water-soluble vitamins dissolve in water. They are found in fruits, vegetables, fresh vegetables, legumes, etc. They are not stored in the body, so excess consumption is excreted in the urine. They include:

  • Vitamin B1 (thiamine)
  • Vitamin B2 (riboflavin)
  • Vitamin B3 (niacin)
  • Vitamin B5 (pantothenic acid)
  • Vitamin B6 (pyridoxine)
  • Vitamin B9 (folate)
  • Vitamin B12 (cobalamin)
  • Vitamin C (ascorbic acid)
  • Vitamin H (biotin)

Minerals

Minerals are inorganic substances that are indispensable for our body’s functions. We need 26 essential minerals in our diet:

  • Major minerals: Calcium, phosphorus, sodium, chlorine, magnesium, iron, sulfur.
  • Trace minerals: Zinc, copper, iodine, chromium, selenium, cobalt.

Calcium

Calcium is abundant in bones and teeth. The daily requirement is:

  • 800-1000mg for children
  • 1200-1400mg for teenagers
  • 800-1000mg for adults
  • More than 2000-2400mg for pregnant and breastfeeding women

Iron

Iron is essential for transporting oxygen in red blood cells. The daily requirement is:

  • 15mg for men
  • 18mg for women
  • 30mg for pregnant women

Phosphorus

Phosphorus is also abundant in bones and teeth. It is found in all foods.

Magnesium

Magnesium is found in all foods, particularly in seeds (nuts, legumes, cereal grains).

Sodium

Sodium (salt) is involved in muscle contractions and neural transmission.

Fluoride

Fluoride is deposited in bones and teeth, strengthening them.

Iodine

Iodine is indispensable for synthesizing thyroid hormones, which regulate metabolism.