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1. Ageing represents a great concern in developed countries because the number of people involved and the pathologies related with it, like atherosclerosis, morbus Parkinson, Alzheimer's disease, vascular dementia, cognitive decline, diabetes and cancer. 2. Epidemiological studies suggest that a Mediterranean diet (which is rich in virgin olive oil) decreases the risk of cardiovascular disease. 3. The Mediterranean diet, rich in virgin olive oil, improves the major risk factors for cardiovascular disease, such as the lipoprotein profile, blood pressure, glucose metabolism and antithrombotic profile. Endothelial function, inflammation and oxidative stress are also positively modulated. Some of these effects are attributed to minor components of virgin olive oil. Therefore, the definition of the Mediterranean diet should include virgin olive oil. 4. Different observational studies conducted in humans have shown that the intake of monounsaturated fat may be protective against age-related cognitive decline and Alzheimer's disease. 5. Microconstituents from virgin olive oil are bioavailable in humans and have shown antioxidant properties and capacity to improve endothelial function. Furthermore they are also able to modify the haemostasis, showing antithrombotic properties. 6. In countries where the populations fulfilled a typical Mediterranean diet, such as Spain, Greece and Italy, where virgin olive oil is the principal source of fat, cancer incidence rates are lower than in northern European countries. 7. The protective effect of virgin olive oil can be most important in the first decades of life, which suggests that the dietetic benefit of virgin olive oil intake should be initiated before puberty, and maintained through life. 8. The more recent studies consistently support that the Mediterranean diet, based in virgin olive oil, is compatible with a healthier ageing and increased longevity. However, despite the significant advances of the recent years, the final proof about the specific mechanisms and contributing role of the different components of virgin olive oil to its beneficial effects requires further investigations.

Assimilation of lipid nutrients depends on the efficiency of emulsified fat hydrolysis by digestive lipases. As shown in vitro, the activity of preduodenal and pancreatic lipases is governed by the physicochemical properties of emulsions. Thus the aim of this study was to evaluate in the rat how emulsions are digested and assimilated depending on their droplet size or solute composition. Fasted rats were intragastrically tube fed emulsions with different median droplet sizes (0.6 microns, fine; 22 microns, coarse) or solute composition (0.8 microns, complex fine) containing 14C-triolein and 3H-cholesterol. Two and 5 hours after feeding, fat-droplet size was measured in gastric and duodenal contents, and lipids were radioactively quantified in different compartments. In the stomach, the droplet size of the fine emulsions significantly increased to values (13 microns to 24 microns) comparable with those of the coarse emulsion (35 microns to 36 microns). In the duodenum, the droplet sizes of the three emulsions were in the range of 14 microns to 33 microns. After 2 hours, gastric triglyceride hydrolysis was significantly higher with the fine than with the coarse emulsion and was lower with the complex fine emulsion. Gastric emptying of fat was significantly different, with the following decreasing order: coarse, fine, and complex fine emulsion. In the small intestine, the fine and coarse emulsions were processed comparably, whereas the assimilation of the fine complex emulsion was significantly delayed. Calculations indicate that ingested fatty acids were distributed in the peripheral tissues at different rates with the same decreasing order. The fate of a lipophilic nutrient, cholesterol, was also markedly altered by the type of emulsion. These data support the concept that tube-fed emulsions with different droplet sizes and solute composition are digested differently and thus are metabolized differently.