Effects of plant sterols and olive oil phenols on serum lipoproteins in humans

The studies described in this thesis investigated whether minor components from vegetable oils can improve health by decreasing cholesterol concentrations or oxidative modification of low-density-lipoprotein (LDL) particles.The plant sterolsβ-sitosterol and sitostanol are known to decrease cholesterol concentrations, but it is not clear whether other chemically related structures have similar effects. We examined the cholesterol-lowering effects of concentrates ofβ-sitosterol and 4,4'-dimethylsterols from rice bran oil and triterpene alcohols from sheanut oil. Plant sterols from rice bran oil lowered serum LDL cholesterol by 9%. This was probably due toβ-sitosterol rather than the 4,4'-dimethylsterols. Triterpene alcohols did not affect serum cholesterol concentration.Oxidative modification of LDL is hypothesised to play a role in the development of atherosclerosis. Extra virgin olive oil contains phenols with antioxidant activity that could prevent oxidative modification of LDL. Three weeks of consumption of phenol-rich olive oil or a single dose of olive oil phenols did not decrease LDL oxidisability, neither in fasting plasma nor postprandial plasma samples. We showed that olive oil phenols reduce LDL oxidisability in vitro , but only in amounts that are much higher than can be reached by olive oil consumption in vivo .The first requirement for an in vivo action of a dietary antioxidant in humans is that it enters the blood circulation. We therefore studied the absorption and urinary excretion of olive oil phenols in humans. We found that apparent absorption of the ingested olive oil phenols was more than 55-66 mol%. Absorption was confirmed by the urinary excretion of at least 5 mol% tyrosol and hydroxytyrosol. A further requirement for a dietary antioxidant to prevent oxidative modification of LDL is that it becomes present in the circulation or in LDL in a form with antioxidant activity. In the body olive oil phenols are extensively metabolised. The antioxidant activity of these phenol metabolites is unknown. To determine the antioxidant activity of olive oil phenols in vivo future studies should focus on the antioxidant activity of the metabolites actually present in plasma rather than on the in vitro antioxidant activity of the phenols as present in the olive oil.In conclusion, although the olive oil phenols are well absorbed, the amount of phenols in olive oil and their consequent attainable plasma concentration in humans is probably too low to reduce LDL oxidisability. Furthermore, our studies provide no evidence that 4,4'-dimethylsterols from rice bran oil or triterpene alcohols from sheanut oil are able to decrease cholesterol concentrations. Thus, there are no indications that the minor components from vegetable oils described in this thesis have important effects on serum lipoproteins

Bioavailability and antioxidant effects of olive oil phenols in humans: a review

Objective: We reviewed the bioavailability and antioxidant effects of phenols from extra virgin olive oil. Search strategy: We searched the MEDLINE database for the years 1966 - 2002. To review the bioavailability of olive oil phenols, we selected animal and human studies that studied the absorption, metabolism, and urinary excretion of olive oil phenols. We also estimated the intake of the various phenols in the Mediterranean area. To review the antioxidant effects of olive oil phenols, we included human and animal studies on the effect of olive oil phenols on markers of oxidative processes in the body. We excluded studies without a proper control treatment and studies in which the antioxidant effects of phenols could not be disentangled from those of the fatty acid composition of olive oil. Results: Bioavailability studies in humans show that the absorption of olive oil phenols is probably larger than 55 - 66 mol%, and that at least 5% is excreted in urine as tyrosol and hydroxytyrosol. Animal studies suggest that phenol-rich olive oil lowers oxidisability of ex vivo low-density lipoprotein (LDL) particles or lowers markers in urine of oxidative processes in the body. In five out of seven human studies, however, these effects of phenols were not found. There are no data on the phenol concentrations in plasma that are attainable by intake of olive oil. We estimated that 50 g of olive oil per day provides about 2 mg or similar to13 mumol of hydroxytyrosol-equivalents per day, and that the plasma concentration of olive oil phenols with antioxidant potential resulting from such an intake can be at most 0.06 mumol/l. This is much lower than the minimum concentrations of these phenols ( 50 - 100 mmol) required to show antioxidant activity in vitro. Conclusion: Although phenols from olive oil seem to be well absorbed, the content of olive oil phenols with antioxidant potential in the Mediterranean diet is probably too low to produce a measurable effect on LDL oxidisability or other oxidation markers in humans. The available evidence does not suggest that consumption of phenols in the amounts provided by dietary olive oil will protect LDL against oxidative modification to any important extent

A patient group based business planning model for a surgical specialty

In this contribution we present an approach for a business planning model for a surgical specialty, based on modelling of all patient processes as well as of the dynamics involved in planning and managing resources. An important basis of the model is the description of the processes of all patient groups served by the specialty. The data for this description are based on the expert knowledge of medical specialists and administrative data from the hospital information system. Furthermore, the planning of scheduled patients and the handling of emergency patients in the model takes into account the workload generated by leading resources, such as operating theatres, for following resources, such as beds. The model allows, therefore, decision support for resource management issues as well as process design issues

A patient group based business planning model for a surgical specialty

In this contribution we present an approach for a business planning model for a surgical specialty, based on modelling of all patient processes as well as of the dynamics involved in planning and managing resources. An important basis of the model is the description of the processes of all patient groups served by the specialty. The data for this description are based on the expert knowledge of medical specialists and administrative data from the hospital information system. Furthermore, the planning of scheduled patients and the handling of emergency patients in the model takes into account the workload generated by leading resources, such as operating theatres, for following resources, such as beds. The model allows, therefore, decision support for resource management issues as well as process design issues