There is now a great deal of scientific evidence on the importance of good eating habits in maintaining health and preventing disease. Thanks to advances in research, it has been possible to understand the different components of food and their role in the body, which has helped to establish a series of recommendations in terms of food and nutrient consumption in order to plan a balanced and healthy per diem expenses .

When we speak of a balanced per diem expenses we cannot refer to a single ideal way of eating for all people, as it has to take into account different aspects. A HEALTHY per diem expenses is one that includes a wide variety of foods in the right amounts, adapted to the characteristics of each person. (age, sex, physiological status and physical activity) and which meets the energy and nutrient requirements of the body to maintain a good nutritional and health status. In recent years, the term "optimal per diem expenses " has emerged, which in addition to the concept of a balanced per diem expenses takes into account a number of other important aspects. For a per diem expenses to be considered optimal, it has to have the following characteristics:

-Balanced: providing all the necessary nutrients in sufficient quantity and in the required proportions.

-Healthy: it is not enough to cover the nutrient requirements, but it is also sought that the per diem expenses has positive health effects through certain compounds that have been shown to have some benefit.

-Pleasant: food plays an important psychological and socio-cultural role. It must also be palatable, so care must be taken with the gastronomic aspects.

-Economic: adapted to the possibilities of each person so that it can be carried out. The best foods are not the most expensive, neither from a nutritional point of view nor from the point of view of their acceptability.

-Safe: at a hygienic level, to avoid food poisoning.

One of the dietary patterns that has been found to be the healthiest worldwide and which is adapted to these characteristics is the Mediterranean per diem expenses , the model dietary pattern that has been followed since ancient times by the countries bordering the Mediterranean Sea. Numerous studies carried out in recent years on the Mediterranean per diem expenses have highlighted the protective role of this dietary pattern against a significant group of diseases, including cardiovascular diseases, diabetes, certain degenerative diseases and cancers of different types.

Food provides us with the nutrients the body needs to carry out its functions properly. Depending on the function they perform, we can classify nutrients as follows:

- Nutrients with energy function: carbohydrates and fats

- Nutrients with structural or plastic function: proteins

- Nutrients with regulatory function: vitamins and minerals

These nutrients are unevenly distributed in foods, so in order for per diem expenses to provide us with all of them in the right amounts, it is advisable to include a wide variety of foods throughout the day. This ensures that we are getting all the nutrients we need.

Foods can be classified according to the predominant nutrient in each food, as depicted in the Food Wheel (SEDCA, 2007):

1. Dairy and dairy products. They are source of proteins and minerals such as calcium.

2. Protein foods. These include meat, fish, eggs and nuts. The latter are also an important source of fat that is very beneficial for cardiovascular health source .

3. Hydrocarbon foods. This includes cereals and their derivatives, tubers and pulses. Pulses, as well as providing carbohydrates, are an important source of vegetable protein source . Whole grains also help to increase the fibre content of per diem expenses.

4. Vegetables. They provide us with water, regulating nutrients (vitamins and minerals) and fibre. They contain antioxidant plant substances of great importance for our health.

5. Fruits. They are source of water, regulating nutrients and fibre. Like vegetables, they contain antioxidants that are important for health.

6. Fats, oils and butters. Within this group , olive oil stands out for its important protective role against cardiovascular diseases.

Food guides teach us in a simple and graphic way how to eat healthily. Below are the per diem expenses Mediterranean pyramid and the Harvard Healthy Eating Plate, which can guide students and workers on healthy eating and healthy lifestyles.