Nutrition

A Primary Need

Life never pauses: in every living being, bodily functions continue incessantly, with only rare exceptions when they slow down, such as during sleep. Life is a constant expenditure of energy and bodily material, and to sustain it, it is continuously necessary to replenish nutrients. This highlights the importance of nutrition, but for it to be effective, it must meet a series of criteria in terms of both quantity and quality.

Nutrition and Nourishment

For humans, the term ‘nutrition’ refers to the selection, preparation, and consumption of food. Nutrition represents the process through which nutrients are taken in, which in turn are responsible for nourishment. Nourishment is a complex set of chemical reactions and physical processes that maintain the body’s chemical composition in a balanced and constant state. These processes primarily act to supply the body with energy and materials lost during daily activities. For example, during youth, proper nutrition supports growth, while in pregnant women it allows the necessary transformations in the maternal body and the healthy development of the fetus. Nutrition also maintains biological defenses and ensures physical and mental efficiency.

Digestion and Absorption

Nutrition and nourishment are two closely linked processes, yet it is not always easy to draw a clear line between them. However, there is an intermediate phase of fundamental importance in which the transition occurs between food intake and its actual use by the body. This phase includes digestion and intestinal absorption.

Digestion is a process that begins in the mouth, continues in the stomach, and is completed in the first part of the intestine, called the duodenum. It involves a series of chemical reactions that break down the large molecules present in food, such as starches, fats, and proteins, into elementary components known as nutrients. During this process, complex carbohydrates, especially starches, are converted into glucose molecules, fats are broken down into fatty acids and glycerol, while proteins are fragmented into amino acids, which contain nitrogen. Other food components with a simpler chemical structure, such as vitamins, minerals, dietary fiber, and antioxidant molecules, undergo minor transformations or remain unchanged. Absorption, also known as assimilation, represents the passage of the final products of digestion through the intestinal walls into the bloodstream and lymphatic system. These food molecules are then transported to cells throughout the body, where they are absorbed and used to support metabolism—the set of chemical reactions and physical-chemical exchanges occurring within the cells themselves.

How Much and What to Eat Every Day

It is complex to define precisely the ideal dietary requirements for each nutrient. They are established for a reference individual, typically an average person in good health, moderately active, and living in normal environmental conditions. Different expert commissions in various countries have sought to determine these requirements to ensure the health of the local population. In Italy, the Italian Society of Human Nutrition (SINU) periodically publishes the Reference Intake Levels for Nutrients and Energy (LARN) for the Italian population. These guidelines indicate the recommended quantities of nutrients for daily consumption, considering eating habits, economic conditions, and the latest scientific discoveries in the field of nutrition.

Recent recommendations do not provide a specific suggestion for an “ideal” daily caloric intake, because energy needs vary from person to person, even at the same age, sex, body type, and level of physical activity. It is recommended that each person evaluate their personal energy needs based on body weight and follow the fundamental principle of dietary balance, which involves a balanced distribution of the three main nutrients in the diet: proteins, carbohydrates, and fats. In a medium-energy diet of 2000–2500 calories per day, carbohydrates should make up the majority of total daily calories, around 55–65%, fats should represent about 25–30%, and proteins should contribute 10–15% of total calories.

Food and Diseases

Nutrition is closely linked to health, and an unbalanced diet can increase the risk of many diseases, such as diabetes, heart disease, obesity, and some forms of cancer. Conversely, a balanced diet rich in nutrients can help prevent these conditions. It is important to monitor the intake of sugars, saturated fats, and salt in the diet to reduce the risk of chronic diseases.

In a healthy individual with adequate physical activity, an appropriate diet is essential to maintain well-being. However, in certain pathological situations, even a theoretically balanced diet may result in malnutrition. This condition can occur when the body is unable to tolerate certain food components, such as gluten or lactose, causing diseases such as celiac disease or gluten and lactose intolerance, respectively. Additionally, there are numerous nutrition-related diseases linked to environmental pollution, poor animal farming practices, and improper food handling. Beyond the better-known foodborne illnesses—such as salmonella, typhoid, cholera, and botulism—new diseases have emerged, such as bovine spongiform encephalopathy, commonly known as “mad cow disease,” or toxin infections caused by aggressive strains of the Escherichia coli bacterium.

The Words of Nutrition

A ‘diet’ is a carefully calibrated nutrition plan in which the number of calories and the amount of various nutrients needed daily are precisely defined. This type of nutrition is personalized according to individual needs, just like a tailored suit. There are different types of diets designed for specific purposes, such as weight loss or gain, pregnancy management, or treatment of certain conditions. On the other hand, a ‘dietary regimen’ is a set of food choices that limits the intake of certain types of foods. For example, a vegetarian regimen is followed when the daily diet is based primarily on plant-based foods, excluding or minimizing the consumption of meat and fish.

What Healthy Nutrition Is

Healthy nutrition is one that provides the body with all the nutrients necessary for its proper functioning without excess or deficiency. This diet should be varied and balanced, include a wide range of foods, and supply adequate calories to support daily activities. Healthy nutrition should also limit the intake of foods high in added sugars, saturated fats, and salt. Furthermore, it should be environmentally sustainable, promoting responsible food production and consumption. A balanced diet contributes to physical and mental well-being, promotes long-term health, and improves quality of life.