Olive oil and the gastrointestinal trait.

Authors: Euro sciences Communication in collaboration with the Atherosclerosis Research Institute in Minster, Germany

Introduction

More and more publications show how much the quality of fatty acids affects the physiology and physiopathology of the gastrointestinal trait. These studies aim to analyse the effect that the different food fatty acids have on the secretion of gastric juice or on the formation of gallstones. Stomach diseases and in particular gallstones are so wide –spread in the western industrialized countries, that they reach a percentage of 38% in Europe and North America.

The secretion of gastric juice

1886 was published the first study by Ewald and Boas on the influence of fatty acids on the gastric function; they noticed that the olive oil used in the meals could inhibit the secretion of gastric acid (6). Since then several studies have shown how fats can block the secretion of gastric acids in different gastrointestinal traits. Almost all the experimentations have used olive oil as food acid. The olive oil in the duodenal trait, reduces the secretion of gastric juice in rats, dogs and men. Some time ago we did not know if this quality was specifically belonging to the olive oil and the monounsaturated fatty acids or if even other food fats could have this role. In 1997 Serrano and his staff compared the effects of monounsaturated fatty acids- enriched diets ( olive oil) versus polyunsaturated fatty acids( sun flower oil) on the gastric secretions. The researchers showed that an olive oil enriched diet, followed for thirty days at least, lowered the gastric acid more than a diet using sunflower oil. Rhee and colleagues studied the mechanic aspects of this inhibiting action of the oleic acid, showing that in the rats this blocking action is helped by a peptic hormone, released in the circulatory stream when the duodenal mucosa encounters the oleic acid. These researches state that the use of olive oil reduces the gastric acid secretion. This action can have positive effects on duodenal and gastric ulcers over all if the therapy target is to block the gastric acid secretion.
Several studies have researched the connection between diet and gallstones. Unfortunately this connection is still not clear because in some of these works the composition of food fatty acids was not determined. Furthermore the comparison between the two studies is very difficult because of the different lay-out and methodologies used to evaluate a diet and diagnose gallstones. One of the first experimentations on the link between food fats and gallstones is the so-called case-control study, realized in 1989 by Linos and his staff. The researchers discovered that the only associable factor was the consumption of animal fats.
It is interesting to stress how the consumption of olive oil protects from this disease. In a recent case-control study, Misciagna and his collaborators observed that the saturated fats are to be listed as risk factors for the formation of gallstones, while the monounsaturated fatty acids tend to protect from this disease. In a perspective study Gillat and his staff observed that Arabians usually assuming more carbohydrates, fibres and unsaturated fatty acid developed this disease less frequently than Jews among whom gallstones are wide-spread. However the researchers concluded that it was impossible to establish which food element could be the cause of this formation,” if there is a direct cause”. A discovery by the Nurses Health Study further confirms the association between food fats and gallstones. The authors noticed an inverse relation between the consumption of vegetal fats and the formation of gallstones. On the other side they observed a meaningful association between the disease and the monounsaturated/polyunsaturated fatty acids.
Bravo and his collaborators showed how the cholesterol secretion in the rats is stimulated both by polyunsaturated and monounsaturated fatty acids. This derives from a higher presence of cholesterol in animals fed with polyunsaturated fatty acids, but not in those animals fed with monounsaturated fatty acids. The researchers concluded that “this could have a key-role in the formation of gallstones”. These discoveries agree with the results of two studies led on hamsters where it was noticed how the saturated fats stimulated the formation of gallstones. Even if all these studies do not give evidence of the relation between diet and calculosis , it has surely been proved so far that a high consumption of saturated fatty acids is a risk factor for the calculosis. On the contrary the use of olive oil and perhaps of polyunsaturated fatty acids is a protective factor against this disease. But some questions are given no solution. In particular it is not clear why some researchers noticed certain effects, unknown for others. Further studies are necessary to clear up these aspects.

Conclusion

The studies realized on the existing link between food fatty acids and the gastrointestinal physiopathology show that a high consumption of monounsaturated fatty acids has beneficial effects on these organs, reducing the gastric acid secretion and preventing from calculosis. It was never deeply researched how these food fatty acids influence other gastrointestinal diseases like esophagitis and stipsis. However some studies suggest a monounsaturated fatty acid-enriched diet could have further positive effects. Barltrop and Oppe observed that the olive oil is absorbed by children better than butter. Ballesta and collaborators demonstrated the olive oil improved digestibility and the metabolic use of food proteins. Moreover the first studies on the effect of the olive oil or the oleic acid on the gastrointestinal motility and the gastric draining show that the oleic- acid- enriched meals slow down draining, favouring the role of deposit played by the stomach. Spiller and his staff observed that the colon worked faster if some oleic acids were added to the meals prepared for the study. Anyway the researchers did not compare it with other fatty acids, so it is still not clear if the observed action is an effect of fats or it is a peculiar characteristic of the monounsaturated fatty acids. Finally, although several questions remain unsolved, it is proved that the consumption of olive oil has beneficial effects on the different metabolic functions of the gastrointestinal trait.