122 CULTIVAR ANALYSIS AND PROSPECTIVE STUDIES No. 35 Olive groves and olive oil It is important, however, to emphasise that this guide does not replace the Portuguese Food Wheel, launched in 2003 as an update to the initial 1977 version, but rather functions as a complement that reinforces and contextualises the existing guidelines (Rodrigues et al., 2006). The Food Wheel is organised into seven food groups represented in different proportions, which indicate each group’s relative contribution to the daily diet, as well as the respective recommended portions. Water is depicted at the centre, highlighting its essential role in the composition of food and in sustaining life. Each group has specific nutritional functions and should form part of the daily diet; it is recommended to vary the foods within each group to ensure dietary diversity and balance. With regard to the fats and oils group, the Food Wheel recommends moderate daily consumption, recognising their nutritional importance but emphasising that the quality of the fat is crucial (FCNAUP, 2003). Indeed, fats differ in their fatty acid composition and their effects on health, which underpins the principle that ‘too much is a mistake and too little is a deficiency’, promoting informed, balanced consumption tailored to the body’s needs (Peres, 1997). This group performs essential functions, notably in supplying essential fatty acids and facilitating the absorption of fat-soluble vitamins; within the context of the Mediterranean diet, this should be achieved primarily through olive oil, as the main source of added fat. Fats perform fundamental nutritional functions in the human body. As well as facilitating the absorption of fat-soluble vitamins, they provide essential fatty acids, which are indispensable for the structure and function of cell membranes and for the regulation of various biological processes, including inflammatory, hormonal and metabolic phenomena. Furthermore, all fats provide approximately 9 kcal per gram, the highest energy density amongst the macronutrients. Thus, although they differ in their nutritional quality, their energy contribution is equivalent, which reinforces the need for moderation in consumption (Peres, 1992; 1997). However, fats do not constitute a homogeneous group; they differ in their fatty acid composition and their physiological effects. They can be classified as saturated, monounsaturated and polyunsaturated, each with distinct nutritional properties. This diversity underscores the importance of prioritising the quality of fat in the diet, guiding informed and balanced choices, since both excess and deficiency can compromise essential biological functions (Peres, 1997). In this regard, it is important to consider not only the composition of fats, but also the way in which they are used in food preparation. In his book Food and Nutrition, Emílio Peres emphasises that olive oil, due to its predominantly monounsaturated structure and the presence of antioxidant compounds, exhibits greater stability when heated compared with oils rich in polyunsaturated fatty acids, such as maize, sunflower or soya oils, as well as with some margarines, which are more susceptible to thermal oxidation. This greater stability does not, however, imply excessive use, but rather appropriate and moderate use, tailored to cooking methods. The author thus highlights the importance of the quality of the fat, the type of culinary preparation and temperature control in preserving the nutritional value of foods and preventing the formation of undesirable compounds (Peres, 1992). Within the context of the Mediterranean diet, olive oil plays a central role as the main source of fat. Among its various categories, virgin olive oils stand out; these are obtained directly from olives using mechanical processes and without recourse to refining processes. Within this group, extra virgin olive oil is of particular importance, distinguished by its higher quality and greater concentration of bioactive compounds.
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