Human Nutrition: Needs, Diets, and Health

Posted on Sep 23, 2025 in Biology

Food and Nutrition Fundamentals

Nutrients are biomolecules that make up our body and are often called proximate principles. Vitamins are essential organic nutrients that need to be part of our diet.

  • Carbohydrates: Found in bread, cereals, pasta, etc.
  • Proteins: Found in animal products and pulses.
  • Mineral Salts: All foods contain mineral salts in varying amounts.
  • Lipids: Found in oil, butter, bacon, etc.
  • Water: We take in water when we drink and also when we consume food.
  • Vitamins: Abundant in vegetables and fresh fruits.

Carbohydrates: Simple and Complex

Carbohydrates are categorized into simple and complex forms:

  • Simple Carbohydrates: These include monosaccharides, like glucose and fructose, and disaccharides, like sucrose and lactose.
  • Complex Carbohydrates: An example is cellulose, contained in vegetable fiber.

Lipids: Energy, Structure, and Regulation

Lipids serve various crucial functions in the body:

  • Fats: Can be saturated or unsaturated. Their primary function is to store energy.
  • Membrane Lipids: These form cell membranes, such as phospholipids and cholesterol.
  • Lipids with Regulatory Functions: Examples include some vitamins (like vitamins A or D) and sexual hormones.

Proteins: Building Blocks of Life

Proteins are formed by amino acid bonds.

Proteins perform a wide range of vital functions:

  • They form structures such as hair, nails, and membranes.
  • They transport oxygen in the blood from the lungs to the tissues.
  • They are involved in the defense against infections.
  • They are responsible for muscle contraction.
  • They regulate biological responses.

Organisms use amino acids found in foods. These foods, when eaten, break down into amino acids. Then they bond again, but in a different order, to create the proteins needed for our cells and tissues.

Mineral Salts: Essential Inorganic Substances

Mineral salts are inorganic substances that have different functions in the body. Some are structural, making up an important part of our bones and teeth, while others allow organs to function correctly or help in the regulation of cellular metabolic reactions.

Water: The Body’s Most Abundant Molecule

Water is the most common molecule in our bodies. Water acts as a solvent for most other nutrients, is essential because it allows our own metabolic reactions to occur, serves as a medium for transporting other substances, and regulates body temperature.

Vitamins: Fat-Soluble and Water-Soluble

Vitamins are categorized based on their solubility:

  • Fat-Soluble Vitamins: The most well-known fat-soluble vitamins are vitamins A and D.
  • Water-Soluble Vitamins: Examples include B1, B2, B12, and vitamin C.

Understanding Nutritional Needs

We need food to obtain nutrients and to satisfy a range of needs:

  • Structural: We need proteins to help us grow and to maintain our bodies.
  • Providing Energy: We need carbohydrates and lipids in order to do sports or to move about.
  • Regulatory: We need a range of minerals for our bodies to function properly.

Structural Needs: Building and Maintaining the Body

The most important structural nutrients are proteins, although certain lipids are also important, such as those that form cell membranes, as are certain salts, such as those that form our skeleton.

Energy Needs: Fueling Body Functions

We get energy from energy nutrients (carbohydrates and fats). When there is a lack of energy nutrients, we can obtain energy from proteins, due to cell respiration that takes place in cells.

Calorific Values:

  • One gram of fat provides 9 kcal.
  • One gram of carbohydrates provides 3.75 kcal.
  • One gram of protein provides 4 kcal.

Basal Metabolic Rate and Energy Use

Basal metabolic rate (BMR) is the minimum amount of energy our body needs when we are resting and completely still.

Formulas for calculating BMR:

  • Men: 66.5 + [13.7 x mass (kg)] + [5 x height (cm)] – [6.7 x age (years)]
  • Women: 55 + [9.5 x mass (kg)] + [4.8 x height (cm)] – [4.7 x age (years)]

Functional and Regulatory Needs: Vitamins and Minerals

Our body needs vitamins and minerals so that all vital processes take place properly. Although our body needs smaller amounts of these nutrients, they are still essential for it to function.

Healthy Diets and Eating Patterns

The quantity of food that someone consumes daily is called a diet.

Balanced Diet: Essential for Health

For a diet to be healthy, it needs to be balanced. This means that it should provide the necessary energy-providing and structural nutrients, and also in the right proportions.

The guidelines for a balanced diet are:

  • Eat a variety of different foods.
  • Have several meals each day.
  • Eat fresh vegetables.
  • Avoid convenience foods.
  • Include unsaturated fats.
  • Eat fiber-rich foods daily.

The Food Wheel: A Visual Guide to Nutrition

  • Milk and Milk Products, Meat, Fish, and Eggs: Rich in protein; their function is mainly structural.
  • Pulses, Potatoes, and Nuts: Contain all nutrients, meeting structural, regulatory, and energy needs.
  • Vegetables and Fruits: Rich in vitamins and minerals; they meet regulatory needs.
  • Cereals, Bread, Pasta: Rich in carbohydrates.
  • Bacon, Butter, and Oil: Rich in fats; meet energy needs.

Mediterranean Diet: A Healthy Lifestyle

The Mediterranean diet incorporates the traditional healthy eating habits found in Southern Europe. Key components include:

  • Olive oil
  • Cereals
  • Pulses
  • Fish
  • Vegetables
  • Fruits

Food Consumption and Supply Chain

It is essential that we understand how the food we eat is acquired and what types of nutrients are present in our diets.

Consumption Habits: Global Nutritional Trends

Nutritional imbalances and illnesses linked to poor diets are prevalent in developed countries. Characteristics often include:

  • A high calorie intake causes obesity.
  • Foods that are rich in cholesterol and saturated fats increase the chances of suffering from circulatory diseases.
  • Refined foods with little fiber can lead to constipation problems.
  • Protein-rich foods that supply amino acids need to be processed. The liver and kidneys have to remove them, placing extra strain on these organs.
  • Consumption of ready-made meals often leads to nutritional deficiencies.

In developing countries, diets often have different characteristics:

  • Diets tend to have a low calorie content.
  • The variety of food is limited.
  • Protein consumption is low.
  • Sanitary conditions are often poor.

The Food Supply Chain: From Production to Consumer

A food supply chain refers to the process that starts when any type of food is produced and ends when it reaches the consumer. Stages include: production, storage, transport, industrial processing, and commercialization. Hygienic conditions are essential throughout this chain.

Methods of Preserving Foods

Common methods of food preservation include sterilization, pasteurization, and vacuum packaging.

Food Additives: Purpose and Use

Additives are natural substances or artificial chemical products that are added to foods for various purposes.

Food-Related Illnesses and Disorders

An inadequate diet can cause changes in our health and lead to illnesses that, in some cases, can be life-threatening.

Malnutrition: A Global Health Challenge

Malnutrition occurs when someone does not have enough to eat. There are many different types of malnutrition, such as marasmus, which is caused by a complete lack of food, and kwashiorkor, which occurs when there is a lack of protein.

Inadequate Nutrition: Health Consequences

  • Deficiency-Related Diseases: Some people cut out certain foods from their diet because they choose to or because they do not have access to those foods, leading to deficiencies.
  • Obesity: When an individual eats disproportionate amounts of energy-providing foods, all the unnecessary nutrients are stored as body fat.
  • Type 2 Diabetes: This is also called adult diabetes. It involves an inability to control the body’s blood sugar levels.

Eating Disorders: Psychological Impact on Diet

These are psychological disorders related to eating habits:

  • Anorexia: People who suffer from this disorder reject food because they have an intense fear of gaining weight.
  • Bulimia: People who suffer from this disorder eat extreme amounts of food in a compulsive way, often followed by compensatory behaviors.

Allergies and Intolerances: Dietary Sensitivities

  • Intolerances: People with this disorder, such as celiac disease, have to eat products that have been made using gluten-free flour.
  • Food Allergies: These are different from intolerances because they provoke an allergic reaction that can cause an anaphylactic shock.

Food Poisoning: Bacterial Contamination

Salmonellosis, which is caused by bacteria, is associated primarily with the consumption of food containing raw eggs.