The human body is host to tril­lions of gut bac­te­ria, also known as micro­biome, that col­lec­tively con­trol many of the bod­ies func­tions includ­ing the immune sys­tem and energy bal­ance. It has now become appar­ent that a cer­tain bal­ance of gut bac­te­ria is opti­mal for human health. In fact, an asso­ci­a­tion has been made to dys­lipi­demia, insulin resis­tance and type 2 dia­betes when an indi­vid­ual devel­ops an imbal­ance in the gut bac­te­ria. It is thought that the changes in bac­te­r­ial diver­sity can pro­mote inflam­ma­tion, insulin resis­tance and meta­bolic syn­drome.

It has been well estab­lished that dietary inter­ven­tions can change the bac­te­r­ial diver­sity and pro­vide a ther­a­peu­tic tool for treat­ing con­di­tions that may be influ­enced by gut bac­te­ria. Two recent stud­ies have explored how the Mediterranean diet (MedDiet) with olive oil influ­ences gut bac­te­ria, insulin sen­si­tiv­ity and meta­bolic syn­drome.

Long-​term con­sump­tion of the Med and LFHCC diets exerts a pro­tec­tive effect on the devel­op­ment of type 2 dia­betes by dif­fer­ent spe­cific changes in the gut micro­biota.- Researchers

The first study, pub­lished last month in the Journal of Clinical Endocrinology and Metabolism, was con­ducted over a period of one year in 20 obese par­tic­i­pants within the Coronary Diet Intervention With Olive Oil and Cardiovascular Prevention (CORDIOPREV) study.

The study com­pared a MedDiet (35 per­cent fat, 22 per­cent monoun­sat­u­rated) to a low-​fat, high com­plex car­bo­hy­drate (LFHCC) diet (28 per­cent fat, 12 per­cent monoun­sat­u­rated) to changes in bac­te­r­ial diver­sity related to insulin sen­si­tiv­ity and type 2 dia­betes. The main fat source for the MedDiet group was olive oil, the research team dis­trib­ut­ing olive oil to all par­tic­i­pants to ensure this was the case.

Both diets showed changes in bac­te­r­ial diver­sity, but in dif­fer­ent ways. The authors say­ing: “Our results sug­gest that long-​term con­sump­tion of the Med and LFHCC diets exerts a pro­tec­tive effect on the devel­op­ment of type 2 dia­betes by dif­fer­ent spe­cific changes in the gut micro­biota, increas­ing the abun­dance of the Roseburia genus and F. praus­nitzii, respec­tively.”

The role of gut bac­te­ria, and the large diver­sity of their nature means this is a fairly com­plex area that is not yet fully under­stood. However, a study pub­lished in PLoS ONE, 2013, sug­gests that Roseburia and F. praus­nitzii are both buryrate-​producing bac­te­ria, that also sup­ply other short chain fatty acids that help reduce oxida­tive stress and inflam­ma­tion.

A sec­ond study, also con­ducted within the CORDIOPREV study, pub­lished last month in the Journal of Nutritional Biochemistry, fol­lowed 239 par­tic­i­pants: 138 par­tic­i­pants with meta­bolic syn­drome and 101 par­tic­i­pants with­out.

At base­line there were notice­able dif­fer­ences in the gut bac­te­ria of both groups. The rel­a­tive abun­dance of Bacteroides, Eubacterium and Lactobacillus gen­era was higher in the par­tic­i­pants with meta­bolic syn­drome. The rel­a­tive abun­dance of 18 other bac­te­r­ial species were lower in the par­tic­i­pants with meta­bolic syn­drome at base­line.

To assess whether the dietary inter­ven­tions had impact on the bac­te­r­ial pro­file, the bac­te­ria were exam­ined again after 2 years. In the MedDiet group the abun­dance of P. dis­ta­so­nis, B. thetaio­taomi­cron, F. praus­nitzii, B. ado­les­cen­tis and B. longum were sig­nif­i­cantly increased in those with meta­bolic syn­drome but not in those with­out. On the other hand, the abun­dance of E. rec­tale increased and P. dis­an­so­nis decreased in the non-​metabolic syn­drome group only.

This study revealed that despite the meta­bolic syn­drome still being present in par­tic­i­pants, sig­nif­i­cant changes to gut bac­te­ria do occur. Most notably, the gut bac­te­ria that improved in abun­dance in the meta­bolic syn­drome group show a neg­a­tive cor­re­la­tion with lev­els of glu­cose, triglyc­erides, and HDL cho­les­terol, sup­port­ing the idea that gut bac­te­ria can indeed influ­ence insulin resis­tance and the devel­op­ment of meta­bolic syn­drome, whereas these changes did not occur in the non-​metabolic syn­drome group.

Researchers sug­gest that it is a com­bi­na­tion of fiber and the phenolic-​compound-​rich foods such as olive oil, veg­eta­bles, fruits, wine and so forth, that con­tribute to these pos­i­tive changes in gut bac­te­ria.

Since it is now well estab­lished that meta­bolic syn­drome is asso­ci­ated with chronic low-​grade inflam­ma­tion, another impor­tant obser­va­tion was that “the con­sump­tion of a Mediterranean diet increased the abun­dance of the Bacteroides genus mem­ber B. thetaio­taomi­cron and F. praus­nitzii, which sug­gest that the con­sump­tion of this diet may increase or main­tain a micro­biota with anti-​inflammatory capa­bil­ity.”



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