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“Mediterranean diet” benefits partly due to oil: study

April 19, 2010
Courtesy of BioMed Central
and World Science staff

In­gre­di­ents of ol­ive oil that sup­press in­flam­ma­tion in the body are partly re­spon­si­ble for the healthy ef­fects of “Mediter­ranean di­ets,” sci­en­tists say in a new re­port.

A Med­i­ter­ra­nean di­et is gen­er­ally con­sid­ered to be one with plen­ty of fruits, veg­eta­bles, legumes, ce­reals, some fish and al­co­hol, and lit­tle dairy and meat. Ol­ives and ol­ive oil are al­so typ­i­cal fea­tures of Med­i­ter­ra­nean di­ets. Such reg­i­mens have been linked to a death ra­te re­duced by half in 70- to 90-year-olds, and ben­e­fits such as low­er risk of car­di­o­vas­cu­lar dis­ease and Alzheimer’s dis­ease.

Part of the ex­plana­t­ion for such effects lies in a family of weakly acid­ic, or­gan­ic chem­i­cal com­pounds called phe­nols, found in ol­ive oil, ac­cord­ing to Fran­cis­co Perez-Jimenez from the Uni­vers­ity of Cor­do­ba, Spain, lead re­search­er in the new stu­dy. 

Phe­nols have ef­fects on genes in­volved in in­flamma­t­ion, he added, a pro­cess in which blood flow to spe­cif­ic parts of the body in­creases as part of an im­mune res­ponse. In­flamma­t­ion can be­come an ab­nor­mal, chron­ic con­di­tion in a num­ber of dis­eases, in­clud­ing heart dis­ease and ar­thri­tis.

The phe­nols in vir­gin ol­ive oil sup­press sev­er­al genes that pro­mote in­flamma­t­ion, said Perez-Jimenez. Vir­gin ol­ive oil is oil squeezed out of ol­ives at rel­a­tively low tem­per­a­tures in a pro­cess known as cold press­ing. Vir­gin and par­tic­u­larly “extra-vir­gin” ol­ive oil, which comes from the first press­ing of the ol­ives, have the high­est phe­nol con­tent, said Perez-Jimenez.

Perez-Jimenez and col­leagues stud­ied the ef­fects of eat­ing a break­fast rich in phe­nol com­pounds on gene ac­ti­vity in 20 pa­tients with met­a­bol­ic syn­drome, a com­mon con­di­tion as­so­ci­at­ed with in­creased risk of car­di­o­vas­cu­lar dis­ease and type 2 di­a­be­tes.

The study par­ti­ci­pants ate con­trolled break­fasts, and for six weeks be­fore the study they had to avoid all drugs, vit­a­min tablets and oth­er sup­ple­ments. “We iden­ti­fied 98 dif­fer­en­tially ex­pressed [ac­tiva­ted] genes when com­par­ing the in­take of phe­nol-rich ol­ive oil with low-phe­nol ol­ive oil,” said Perez-Jimenez.

“Sev­eral of the re­pressed genes are known to be in­volved in pro-in­flam­ma­to­ry pro­cesses,” he added. That sug­gests the di­et can switch the ac­ti­vity of im­mune sys­tem cells to a less harm­ful “in­flam­ma­to­ry pro­file,” he added.

“These find­ings strength­en the rela­t­ion­ship be­tween in­flamma­t­ion, obes­ity and di­et and pro­vide ev­i­dence at the most bas­ic lev­el of healthy ef­fects de­rived from vir­gin ol­ive oil con­sump­tion in hu­mans. It will be in­ter­est­ing to evalua­te wheth­er par­tic­u­lar phe­nolic com­pounds car­ry these ef­fects, or if they are the con­se­quence of a syn­er­gic ef­fect” of the en­tire group of phe­nol com­pounds, he said.

The study is pub­lished in the re­search jour­nal BMC Ge­nomics.

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Ingredients in olive oil that suppress inflammatory processes in the body are partly responsible for the good health effects of “Mediterranean diets,” scientists say in a new report. A Mediterranean diet is generally considered to be one with plenty of fruits, vegetables, legumes, cereals, some fish and alcohol, and little dairy and meat. Olives and olive oil are also typical features of Mediterranean diets. Such regimens have been linked to a death rate reduced by half in 70- to 90-year-olds, and benefits such as lower risk of cardiovascular disease and Alzheimer’s disease. Part of the explanation lies in a family of weakly acidic, organic chemical compounds called phenols, found in olive oil, according to Francisco Perez-Jimenez from the University of Cordoba, Spain, lead researcher in the new study. Phenols have specific effects on genes involved in inflammation, he added, a process in which blood to specific parts of the body increases in order to carry immune system chemicals to that place. Inflammation can become an abnormal, chronic condition in a number of diseases, including heart disease and arthritis. The phenols in virgin olive oil suppress several genes that promote inflammation, said Perez-Jimenez. Virgin olive oil is oil that is squeezed out of olive fruits at relatively low temperatures, a process known as cold pressing. Virgin and particularly “extra-virgin” olive oil, which comes from the first pressing of the olives, have the highest phenol content, said Perez-Jimenez. Perez-Jimenez and colleagues studied the effects of eating a breakfast rich in phenol compounds on gene activity in 20 patients with metabolic syndrome, a common condition associated with increased risk of cardiovascular disease and type 2 diabetes. The study participants ate controlled breakfasts, and for six weeks before the study they had to avoid all drugs, vitamin tablets and other supplements. “We identified 98 differentially expressed [activated] genes when comparing the intake of phenol-rich olive oil with low-phenol olive oil,” said Perez-Jimenez. “Several of the repressed genes are known to be involved in pro-inflammatory processes,” he added. That suggests the diet can switch the activity of immune system cells to a less harmful “inflammatory profile,” he added. “These findings strengthen the relationship between inflammation, obesity and diet and provide evidence at the most basic level of healthy effects derived from virgin olive oil consumption in humans. It will be interesting to evaluate whether particular phenolic compounds carry these effects, or if they are the consequence of a synergic effect” of the entire group of phenol compounds, he said. The study is published in the research journal BMC Genomics.