A study in Spain found that early inter­ven­tion with a Mediterranean diet sup­ple­mented with addi­tional extra vir­gin olive oil (EVOO) and pis­ta­chios reduces the inci­dence of ges­ta­tional dia­betes mel­li­tus (GDM) and improves out­comes for mother and baby.

According to the American Diabetes Association, GDM is an impor­tant pub­lic health prob­lem, cre­at­ing com­pli­ca­tions in seven per­cent of all preg­nan­cies. The preva­lence of GDM is increas­ing as obe­sity, seden­tary lifestyle, and older age at preg­nancy become more com­mon.

Previous stud­ies have revealed that adher­ence to the Mediterranean diet decreases the risk of GDM, but this is the first ran­dom­ized, con­trolled study of how a sup­ple­mented Mediterranean diet influ­ences rates of GDM, as well as pre­ma­ture birth, emer­gency cesarean sec­tion, and per­ineal trauma.

For this study, con­ducted by the San Carlos Clinical Hospital in Madrid, 2,418 women were invited to par­tic­i­pate when they came for their first preg­nancy ultra­sound, between eight and twelve weeks. Out of that num­ber, 1,000 met the ini­tial study cri­te­ria of being 18 years of age or older, hav­ing no intol­er­ance to nuts or EVOO, and expe­ri­enc­ing their first preg­nancy. Any med­ical con­di­tions or drug ther­apy that might com­pro­mise the effec­tive­ness of the test diet were also ruled out. Of 1,000, 874 stayed with the study and par­tic­i­pated all the way through the birth of their babies.

Participants were ran­domly assigned to either the inter­ven­tion group (IG) or the con­trol group (CG). Both groups were given the same basic Mediterranean guide­lines, which included two or more daily serv­ings of veg­eta­bles, three or more serv­ings of fruit (except­ing fruit juices), three daily serv­ings of skimmed dairy prod­ucts and whole grain cere­als, two to three weekly serv­ings of legumes, and mod­er­ate to high con­sump­tion of fish.

They were also asked to con­sume low amounts of red and processed meats, and avoid refined grains, processed baked goods, pre-sliced bread, soft drinks, fresh juices, fast foods and pre-cooked meals. In addi­tion, it was rec­om­mended that they walk at least 30 min­utes a day.

In addi­tion to the basic rec­om­men­da­tions, the 434 par­tic­i­pants in the inter­ven­tion group received guid­ance from dieti­tians a week before the study start. They were advised to con­sume at least 40 mL of EVOO and a hand­ful (25 – 30 grams) of pis­ta­chios daily. To ensure that they had access to the min­i­mum amount of rec­om­mended oil and nuts, each IG par­tic­i­pant received 10 liters of EOO and two kilo­grams of roasted pis­ta­chios.

By con­trast, the 440 con­trol group par­tic­i­pants were advised by their mid­wives to restrict con­sump­tions of dietary fat, includ­ing nuts and EVOO.

For the length of their preg­nan­cies, both the IG and CG had the same stan­dard-prac­tice lab­o­ra­tory eval­u­a­tions, at 24 – 28 week’s ges­ta­tion, at 36 – 38 weeks (third trimester), and at deliv­ery. For both groups, nutri­tional guid­ance was rein­forced at each visit. Up until deliv­ery, all were screened for ges­ta­tional dia­betes, ges­ta­tional weight gain, and preg­nancy-induced hyper­ten­sion. Individual dietary rec­om­men­da­tions were given in cases where the patient might be con­sum­ing too many calo­ries.

With the same fre­quency of guid­ance, test­ing and health-provider inter­ven­tion, the ges­ta­tional and birth expe­ri­ences of the inter­ven­tion and con­trol groups were sig­nif­i­cantly dif­fer­ent.

Of the 974 study par­tic­i­pants, 177 were diag­nosed with ges­ta­tional dia­betes. Those with GDM in the con­trol group num­bered 103, while those in the inter­ven­tion group — the group whose diet included addi­tional EVOO and pis­ta­chios — num­bered 74. In addi­tion, those in the IG with ges­ta­tional dia­betes had sig­nif­i­cantly reduced rates of insulin-treated GDM. And fewer of those diag­nosed with GDM in the IG required insulin than those diag­nosed with GDM in the CG.

In addi­tion to expe­ri­enc­ing fewer inci­dences of GDM, the inter­ven­tion group bore fewer babies with low birth weight. According to the Children’s Hospital of Philadelphia, “Low birth­weight is a term used to describe babies who are born weigh­ing less than 2,500 grams (5 pounds, 8 ounces).

In con­trast, the aver­age new­born weighs about 8 pounds.” In the con­trol group, 17 babies were assessed to have low birth weight, com­pared to only five babies with low birth weight in the inter­ven­tion group. In addi­tion, twenty-five of the con­trol group babies were con­sid­ered small for their ges­ta­tional age, com­pared with five in the inter­ven­tion group.

In addi­tion, at the time of birth, fewer moth­ers in the IG group expe­ri­enced preg­nancy-induced hyper­ten­sion, per­ineal trauma, and uri­nary tract infec­tions. And, while nutri­tional coun­sel­ing was pro­vided to both groups, par­tic­i­pant ges­ta­tional weight gain was sig­nif­i­cantly lower at 24 – 28 weeks and at 36 – 38 weeks for par­tic­i­pants in the inter­ven­tion group.

There have been pre­vi­ous stud­ies of nutri­tional inter­ven­tion in ges­ta­tional dia­betes using a vari­ety of dietary guide­lines, includ­ing alter­nate Mediterranean (aMED), Dietary Approaches to Stop Hypertension (DASH), and alter­nate Healthy Eating Index (aHEI) dietary pat­terns.

The inter­ven­tions used in these were dif­fer­ent than the present study. Some stud­ies based their rec­om­men­da­tions on the restric­tion of sat­u­rated fats and con­sump­tion of car­bo­hy­drates with a low-glycemic index. While other stud­ies pro­vided rec­om­men­da­tions like this one, this is the first study to mea­sure the results of specif­i­cally increas­ing EVOO and nuts in the diets of preg­nant women, as well as pro­vid­ing free sup­plies to par­tic­i­pants.

According to the results of this study, increased EVOO and pis­ta­chio con­sump­tion were clearly ben­e­fi­cial. As a rich source of monoun­sat­u­rated fatty acids, EVOO is known to lower glu­cose lev­els after eat­ing and reduce inflam­ma­tion.

Researchers also hypoth­e­size that in this study’s pop­u­la­tion, the lib­eral use of olive oil may have facil­i­tated an increased intake of veg­eta­bles, which are tra­di­tion­ally eaten with olive oil in Spanish cui­sine.


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