`Study: EVOO-Rich Diet Improved Weight and Insulin Sensitivity in Mice with Liver Disease - Olive Oil Times

Study: EVOO-Rich Diet Improved Weight and Insulin Sensitivity in Mice with Liver Disease

By Paolo DeAndreis
May. 21, 2021 13:19 UTC

Extra vir­gin olive oil con­sump­tion had a pos­i­tive impact on two comor­bidi­ties of non-alco­holic fatty liver dis­ease – obe­sity and dia­betes – in mice, accord­ing to the results of a recent study.

However, researchers also found that exces­sive intake of extra vir­gin olive oil in a high-fat diet caused the same liver dam­age as a diet high in sat­u­rated fats.

To our sur­prise, the extra vir­gin olive oil intake did not improve the liver dam­age caused by high-fat diets. However, extra vir­gin olive oil intake was able to improve body weight and insulin resis­tance.- Franz Martín and Robert Kleemann, study authors

The study, which was pub­lished in Nature, inves­ti­gated the impact of dif­fer­ent types of high-fat diets and one low-fat diet on non-alco­holic fatty liver dis­ease, a con­di­tion often derived from obe­sity and asso­ci­ated with insulin resis­tance.

The pres­ence of non-alco­holic fatty liver dis­ease is cor­re­lated with a higher risk of stroke, dia­betes and heart dis­ease.

See Also:Grant Recipient to Study Impacts of Polyphenols on DNA Function

Our study was designed to explore the mech­a­nisms of the pos­i­tive effects of extra vir­gin olive oil intake,” Franz Martín and Robert Kleemann, two authors of the study, told Olive Oil Times.

What we did was ana­lyze extra vir­gin olive oil com­po­si­tion, mainly sterols and phe­nols, and then explore the effects of extra vir­gin olive oil high-fat diets on the traits related to non-alco­holic fatty liver dis­ease and type 2 dia­betes,” the researchers added, refer­ring to traits such as body weight, plasma lipid pro­file, glu­cose home­osta­sis, insulin sen­si­tiv­ity and his­tol­ogy mark­ers of liver dam­age.

The research exam­ined the effects of high-fat diets based on lard, extra vir­gin olive oil and extra vir­gin olive oil enriched with polyphe­nols against the effects of a low-fat diet.

To our sur­prise, the extra vir­gin olive oil intake did not improve the liver dam­age caused by high-fat diets,” the two researchers said. Thus, in the case of high-fat diets based on extra vir­gin olive oils, there were no rel­e­vant dif­fer­ences in liver dam­age when com­pared with sat­u­rated fats in high-fat diets.”

However, extra vir­gin olive oil intake was able to improve body weight and insulin resis­tance,” they added.

According to the researchers, the study shows that exces­sive con­sump­tion of healthy oils over long peri­ods may dam­age the liver because those oils accu­mu­late in the cells.

In the begin­ning, healthy oils can reduce inflam­ma­tion, but if you accu­mu­late high amounts of good’ fatty acids in a cell, this cell will become dys­func­tional because all cel­lu­lar processes are ham­pered due to the sheer phys­i­cal over­load with lipids,” Martín and Kleemann said.

In other words, explained the researchers, if one eats too much, even from healthy prod­ucts, they may undergo adverse long-term effects.”

It is extremely impor­tant to acti­vate metab­o­lism with exer­cise so that the ben­e­fi­cial lipids con­sumed are processed and uti­lized by the body,” Martín and Kleemann added. Then, the real health effects of unsat­u­rated lipids may have a much greater role because, if they are stored in vesi­cles as triglyc­erides, they can­not exert bioac­tive health effects.”

The study also demon­strated how the level of polyphe­nols present in the two types of extra vir­gin olive oil high-fat diets did not have much impact on the out­come.

See Also:Tips for Selecting High-Polyphenol Olive Oils

We saw that the intake of an extra vir­gin olive oil that was much richer in polyphe­nols did not add any dif­fer­ence,” Martín and Kleemann said. The effect was sim­i­lar to the other extra vir­gin olive oil.”

The rea­son could be that extra vir­gin olive oil already con­tains suf­fi­cient lev­els of polyphe­nols and more polyphe­nols do not add any­thing,” they added. Thus, some­times more is not bet­ter.”


The researchers con­cluded that nei­ther a low-fat diet nor an extra vir­gin olive oil-based high-fat diet was bet­ter at pre­vent­ing non-alco­holic fatty liver dis­ease.

However, all the evi­dence sug­gests that the best way to pre­vent non-alco­holic fatty liver dis­ease is a nor­mal-caloric healthy and var­ied diet, together with phys­i­cal activ­ity,” Martín and Kleemann said. To date, there is no other way.”

Concerning the issue of insulin resis­tance, our data from this and other stud­ies point to the fact that extra vir­gin olive oil intake improves insulin sen­si­tiv­ity,” they added.

By com­par­ing the effects of dif­fer­ent diets, the researchers also could bet­ter explore how extra vir­gin olive oil con­sump­tion affects the poten­tial muta­tion of liver gene expres­sion.

The con­stant intake of extra vir­gin olive oils, for long peri­ods, affected the expres­sion of genes involved in oxida­tive stress, inflam­ma­tion, lipids metab­o­lism and fibro­sis in the liver,” Martín and Kleemann said. This is the rea­son why mouse liv­ers were unable to improve the dam­age caused by high-fat hyper-caloric diets, despite the intake of healthy fats.”

However, the two sci­en­tists stressed that these find­ings were made in mice and could not be auto­mat­i­cally cor­re­lated with humans. The rea­son for this, the researchers said, was the mice were eat­ing far larger quan­ti­ties of extra vir­gin olive oil and polyphe­nols, rel­a­tive to their over­all caloric intake, than humans nat­u­rally would.

We believe that olive oils, even those with high polyphe­nols, are one of the most ben­e­fi­cial con­sumer oils we have avail­able,” Martín and Kleemann said. A big dif­fer­ence between all kinds of mouse stud­ies and reg­u­lar human olive oil con­sump­tion is that the mice get the same food every day.”

In the future, the researchers said that they hope to test olive oil in alter­nate dietary reg­i­mens and com­pare these with other con­sumer oils or dietary fats.

The real ben­e­fit of con­sum­ing olive oil may be the abil­ity to restore and quench dys­meta­bolic or inflam­ma­tory processes evoked by other com­po­nents of the diets, such as car­bo­hy­drates, pro­teins, other oils and so on,” Martín and Kleemann said. Because of the prop­er­ties of olive oil, it can be expected that olive oil may be more pow­er­ful in restor­ing dys­me­tab­o­lism and asso­ci­ated inflam­ma­tion rel­a­tive to other con­sumer oils.”

Regarding the effect of polyphe­nols, alter­nat­ing a diet should also be con­sid­ered by future stud­ies.

The effects observed in our study sug­gest that if high amounts of polyphe­nols are con­sumed with every bite eaten, this may be neg­a­tive for the body’s own endoge­nous antiox­i­dant sys­tems,” Martín and Kleemann said. It is pos­si­ble that the endoge­nous antiox­i­dant sys­tems are down-reg­u­lated in response to the con­stant intake of polyphe­nols at rel­a­tively high lev­els.”

In future stud­ies, we should try to mimic a more alter­nated con­sump­tion of these dietary good­ies so that the body’s antiox­i­dant sys­tems do not become lazy and remain active as well,” they con­cluded. Thus nutri­tional antiox­i­dants plus the body’s mech­a­nisms should act in con­cert and syn­er­gis­ti­cally instead of replac­ing each other.”


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