`Olive Oil Benefits are in the Genes

Health

Olive Oil Benefits are in the Genes

May. 4, 2010
Olive Oil Times Staff

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Sci­en­tists have explained why a Mediter­ranean-style diet is so healthy.

This research was in 20 vol­un­teers who had increased risk of car­dio­vas­cu­lar dis­ease. They were given meals con­tain­ing vir­gin olive oil with either high or low lev­els of cer­tain com­pounds, known as phe­nols. After the meal, researchers looked at the effects on var­i­ous genes in white blood cells. They found that a meal con­tain­ing vir­gin olive oil high in phe­nols reduced the activ­ity of some of the genes involved in inflam­ma­tion com­pared to a meal con­tain­ing vir­gin olive oil lower in phe­nols. Inflam­ma­tion plays a role in the build-up of fatty deposits in blood ves­sels, which can lead to heart attacks and strokes.

Due to the small size and nature of this study, it is dif­fi­cult to link the changes in gene activ­ity to longer-term health con­di­tions.

This study, partly funded by the Cen­tre of Excel­lence in Research on Olive Oil in Spain and the Span­ish government’s Agency for Olive Oil, con­tributes to our under­stand­ing of the effect of olive oils on our cells. How­ever, it is only a very small piece of the com­plex puz­zle of how diet affects our health. It is not pos­si­ble to say with cer­tainty whether the changes in gene activ­ity seen in this study con­tribute to the reduc­tion in risk of car­dio­vas­cu­lar dis­ease attrib­uted to the Mediter­ranean diet.

Where did the story come from?

The research was car­ried out by Dr Anto­nio Camargo and col­leagues from the Uni­ver­sity of Cor­doba and other research cen­tres in Spain and the US. The study was funded by var­i­ous Span­ish gov­ern­ment agen­cies and research cen­tres, includ­ing the Min­istry of Health, Cen­tre of Excel­lence in Research on Olive Oil and Agency for Olive Oil (part of the Span­ish Min­istry of the Envi­ron­ment and Rural and Marine Affairs). The study was pub­lished in the peer-reviewed open access jour­nal BMC Genomics.

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What kind of research was this?

This ran­domised con­trolled trial looked at the effects of par­tic­u­lar chem­i­cal com­pounds, called phe­nols, on the activ­ity of genes in white blood cells. Phe­nols are found in vir­gin olive oil. The researchers were inter­ested in whether vir­gin olive oils with dif­fer­ent lev­els of phe­nol com­pounds had dif­fer­ent effects on gene activ­ity.

The Mediter­ranean diet, which is rich in olive oil, is asso­ci­ated with a reduced risk of car­dio­vas­cu­lar dis­ease. The researchers thought that this reduced risk might in part be attrib­uted to vir­gin olive oils that are high in phe­nols affect­ing genes in the body.

A ran­domised con­trolled trial is the best way to com­pare the effect of dif­fer­ent inter­ven­tions. One poten­tial design weak­ness is that par­tic­i­pants received both types of meal in a ran­dom order. In the­ory, this can result in some car­ry­over” of the effects of whichever inter­ven­tion was received first. How­ever, the researchers included a period of a week between the meals, which should reduce the chance of this hap­pen­ing.

What did the research involve?

The researchers recruited 20 vol­un­teers (aver­age age 56) and fed them two break­fasts, which con­tained vir­gin olive oils with either high or low lev­els of phe­nols. The researchers mea­sured the activ­ity of genes in the vol­un­teers’ white blood cells to see if the meals had dif­fer­ent effects.

The vol­un­teers all had meta­bolic syn­drome. This is a col­lec­tion of char­ac­ter­is­tics that together pre­dict an increased risk of car­dio­vas­cu­lar dis­ease, such as high blood pres­sure and being over­weight with most of the fat car­ried around the waist. They did not show signs of chronic dis­eases of the heart, liver, kid­neys or thy­roid, or have a fam­ily his­tory of early onset car­dio­vas­cu­lar dis­ease. For six weeks before the study began and through­out it, the vol­un­teers were all asked to eat a sim­i­lar low-fat, car­bo­hy­drate-rich diet. The day before each test break­fast, the vol­un­teers were asked to avoid phe­nol-rich foods, such as juices, wine, grape juice, choco­late, cof­fee, tea, olive oil or soy, and not to do intense phys­i­cal exer­cise. They also fasted for 12 hours before the test break­fasts.

The vol­un­teers received two break­fasts on two sep­a­rate days a week apart. The break­fasts con­sti­tuted 60g of white bread and 40ml of olive oil that was either high or low in phe­nols. The low-phe­nol oil was made from the high-phe­nol oil using chem­i­cal processes to extract some of the phe­nols. The researchers and vol­un­teers did not know who had received which break­fast, and the order in which they were given the high- or low-phe­nol break­fast was cho­sen at ran­dom.

Blood sam­ples were taken before and after the two break­fasts, and a spe­cific group of white blood cells was iso­lated. The researchers then looked for changes in the activ­ity of selected genes in these cells after the dif­fer­ent break­fasts.

What were the basic results?

The two dif­fer­ent break­fasts were asso­ci­ated with dif­fer­ing lev­els of activ­ity in 98 genes in the white blood cells. Many of these genes (39 genes) play roles in inflam­ma­tion, and most of them (35 out of the 39) were less active after the break­fast con­tain­ing high-phe­nol vir­gin olive oil than after the break­fast con­tain­ing low-phe­nol vir­gin olive oil.

Inflam­ma­tion plays a role in the build-up of fatty deposits in the blood ves­sels, which can lead to heart attacks, strokes and other car­dio­vas­cu­lar prob­lems.

How did the researchers interpret the results?

The researchers con­cluded that eat­ing a break­fast con­tain­ing vir­gin olive oil high in phe­nol com­pounds reduces the activ­ity of sev­eral genes that pro­mote inflam­ma­tion. They say that this could partly explain the reduc­tion in car­dio­vas­cu­lar dis­ease in Mediter­ranean coun­tries, where vir­gin olive oil is the main source of fat in the diet. They acknowl­edge that other lifestyle fac­tors are likely to con­tribute to this effect.

Conclusion

This small study looked at whether vir­gin olive oils that are high or low in phe­nols have dif­fer­ent effects on gene activ­ity in white blood cells. There are a num­ber of points to note:

  • The small size of the study and the fact that all par­tic­i­pants had meta­bolic syn­drome mean that results may not be rep­re­sen­ta­tive of all indi­vid­u­als with meta­bolic syn­drome or of peo­ple with­out the con­di­tion.
  • The study only looked at gene expres­sion after one meal. It is unclear whether the same results would be seen over a longer period, or how long after the meal these effects are sus­tained.
  • As the par­tic­i­pants were only fed a sin­gle meal con­tain­ing the oils, and their long-term car­dio­vas­cu­lar out­comes were not fol­lowed up, it is not pos­si­ble to say whether the changes in gene activ­ity seen would affect the risk of these out­comes.

This study con­tributes to our under­stand­ing of the effect of phe­nols on gene expres­sion in white blood cells. How­ever, it is only a very small piece of the com­plex puz­zle of how diet affects our health. It is very dif­fi­cult to say whether the changes seen are respon­si­ble for some of the reduc­tion in car­dio­vas­cu­lar dis­ease from eat­ing a Mediter­ranean diet and, if so, what the extent of their effect is.

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