Entry #: 21
Date: 23 November 2017
Section: Mediterranean diet
Topic: Mediterranean diet and gestational diabetes
Type: Human volunteer trial

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Expert review of literature related to olives and olive oil

D. Elizabeth McCord, Nancy B. Ray and Tom C. Karagiannis

Title

A Mediterranean diet with additional extra virgin olive oil and pistachios reduces the incidence of gestational diabetes mellitus (GDM): A randomized controlled trial: The St. Carlos GDM prevention study

Author(s)

Assaf-Balut et al

Citation / Year

(1) / 2017

Keywords

Mediterranean diet, extra-virgin olive oil, pistachios, dietary intervention, gestational diabetes mellitus

Summary

This human volunteer trial builds upon previous studies which have shown that a Mediterranean diet with extra-virgin olive oil and nuts reduces type 2 diabetes and cardiovascular disease (2, 3). Further, previous meta-analysis has indicated that the Mediterranean diet is associated with a decreased risk in gestational diabetes mellitus (4). The current work represents a prospective randomised human volunteer trial, extending previous work from the authors (5), aimed at examining the effects of a Mediterranean diet with extra-virgin olive oil and nuts (pistachios) on the incidence of gestational diabetes mellitus and several maternal (for example, pregnancy-induced hypertension, preeclampsia, urinary tract infection) and neonatal (for example, gestational age at birth and prematurity defined as <37 gestational weeks), parameters. The trial, conducted by the Obstetrics Department at the Clinico San Carlos Hospital in Madrid (Spain), involved the evaluation of a total 2418 women at their first gestational visit (between 8-12 gestational weeks), for potential inclusion in the study. A total of 1000 women who met the inclusion criteria were invited to participate, and were randomised into two groups (n=550 each): the intervention group (a total of 440 completed the study), and the control group (a total of 434 completed the study). Women were recruited at visit 1 (12-14 gestational weeks), and follow-ups were conducted at visit 2 (24-28 gestational weeks), visit 3 (36-38 gestational weeks), and at delivery. The primary outcome was the onset of gestational diabetes mellitus at visit 2 (24-28 gestational weeks).

Key points and implications

Both the intervention and control groups were given the same fundamental dietary advice namely, to consume a Mediterranean-type diet typified by the consumption of vegetables, fruit, skimmed dairy products and relatively high consumption of fish. The key feature of the intervention group was the consumption of at least 40 mL extra-virgin olive oil and 25-30 g of pistachios, whereas, the control group was asked to minimise intake of the consumption of dietary fat particularly from extra-virgin olive oil and nuts. To encourage compliance the women in the intervention group were supplied with 2 x 10L extra-virgin olive oil (amounting to 1L per week for the duration of the study) and 2kg roasted pistachios (amounting to 150g per week for the duration of the study). Overall, the findings indicated that a total of 177 women were diagnosed with gestational diabetes mellitus at 24-28 gestational weeks with 103/440 (23.4%) in the control group and 74/434 (17.1%) in the intervention group. Similarly, beneficial effects of the Mediterranean diet supplemented with extra-virgin olive oil and pistachios were observed for a range of maternal (anthropometric and biochemical), and neonatal parameters (including size and prematurity). Overall, this study highlights the beneficial effects of a Mediterranean diet supplemented with extra-virgin olive oil and pistachios in pregnancy and, indicates potential of relatively simple dietary intervention for the reduction in the incidence of gestational diabetes mellitus.

Related publications

  1. C. Assaf-Balut et al., A Mediterranean diet with additional extra virgin olive oil and pistachios reduces the incidence of gestational diabetes mellitus (GDM): A randomized controlled trial: The St. Carlos GDM prevention study. PloS one 12, e0185873 (2017).
  2. J. Salas-Salvado et al., Reduction in the incidence of type 2 diabetes with the Mediterranean diet: results of the PREDIMED-Reus nutrition intervention randomized trial. Diabetes care 34, 14-19 (2011).
  3. R. Estruch et al., Primary prevention of cardiovascular disease with a Mediterranean diet. The New England journal of medicine 368, 1279-1290 (2013).
  4. V. Izadi et al., Adherence to the DASH and Mediterranean diets is associated with decreased risk for gestational diabetes mellitus. Nutrition 32, 1092-1096 (2016).
  5. C. Assaf-Balut et al., Gestational diabetes mellitus treatment reduces obesity-induced adverse pregnancy and neonatal outcomes: the St. Carlos gestational study. BMJ open diabetes research & care 4, e000314 (2016).