Mediterranean Diet and EVOO Reduce Incidence of Gestational Diabetes

Researchers in Madrid discover that pregnant women who add more EVOO and pistachios to their diets have healthier pregnancies and healthier babies.

By Elyse Schear
Oct. 30, 2017 12:00 UTC

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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