Oxidative products created during cooking and gastro-intestinal digestion are associated with adverse health consequences. Lipid peroxidation is associated with free radical production and age-related disease.

Italian researchers conducted in vitro studies to shed light on the role of extra virgin olive oil and its phenolic composition in limiting the peroxidative phenomena on meat lipids during digestion.

The results showed an interesting paradox: The effects on meat lipids during digestion differed based on the amount of extra virgin olive oil and its phenolic composition.

When grilled turkey breast meat meals were supplemented with a low concentration (2.5 percent) of extra virgin olive oil respective to meat, researchers observed significant reductions of lipid hydroperoxides.

During gastric digestion, generation of lipid hydroperoxides were reduced by 59.9 percent. The levels further dropped to near zero at the end of pancreatic digestion.

Advanced lipoxidation end products (thiobarbituric acid-reactive substances or TBA-RS) averaged 34 percent inhibition at both the end of gastric digestion and pancreatic digestion.

A very different result emerged when extra virgin olive oil extracts were substituted at 5 percent and 10 percent concentrations. The researchers were surprised to find an unexpected increase in the amount of lipid hydroperoxides at all times of digestion. Yet TBA-RS production was inhibited by the addition of phenolic-rich fractions to turkey breast meat.

Two factors most likely contribute to the differences. The olive extract contained a particular class of phenolic compounds, hydroxytyrosol-derivatives. The scientists believe these behaved as pro-oxidants. At the same time, catalyzers from the meat in the digestive system induced the peroxidation of extra virgin olive oil fatty acids, which the authors noted, “was further intensified by the pro-antioxidant activity of extra olive oil phenolic compounds.”

“Our findings suggest that extra virgin olive oil phenolic compounds may act at different levels,” the authors wrote. “Since the phenolic composition of extra virgin olive oil is greatly variable depending on the cultivar and agro-climatic factors (such as growing, harvesting time, seasonal variability), it is plausible that different extra virgin olive oils with different phenolic composition (i.e. high in tyrosol-derivative and low in hydroxytyrosol-derivative) may have a different impact on oxidative phenomena on lipids. Therefore, it is of paramount importance to study the phenolic composition of antioxidant-rich foods used in this type of study to better understand their impact on lipid peroxidation during the digestion of meat.”

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