Tree nuts, predominately walnuts, and extra virgin olive oil featured as key foods in a new clinical trial that assessed the impact of a Mediterranean diet on maternal and fetal outcomes
Credit: California Walnut Commisson
FOLSOM, Calif., July 24, 2019 – A new clinical trial found women who followed a Mediterranean-style diet during pregnancy, including a daily portion of tree nuts (half being walnuts) and extra virgin olive oil, had a 35 percent lower risk of gestational diabetes and on average, gained 2.75 pounds less, compared to women who received standard prenatal care.(1)
A Mediterranean-style diet rich in good, unsaturated fats, found in foods like walnuts and extra virgin olive oil, has been shown to reduce the risk of heart attack, stroke, and cardiovascular death in adults, according to the landmark PREDIMED study.(2) Walnuts, in particular, are a traditional food in the Mediterranean diet because of their omega-3 ALA content (2.5g/oz – the only nut significantly high in this essential fatty acid) and bioactive compounds. While there has been extensive research on the Mediterranean diet to date, the diet’s potential to improve maternal and offspring outcomes has not been widely evaluated, making this study particularly valuable.
Conducted by researchers at Queen Mary University of London and the University of Warwick, this new study included 1,252 multi-ethnic inner-city pregnant women with metabolic risk factors, including obesity and chronic hypertension. In addition to receiving folic acid and vitamin D supplementation, the women were randomly assigned to either a Mediterranean-style diet or a control group that received dietary advice per UK national recommendations for prenatal care and weight management during pregnancy.
Those who followed the Mediterranean diet consumed a daily portion of nuts (30g/day; 15g walnuts, 7.5g almonds, 7.5g hazelnuts) and used extra virgin olive oil (0.5L/week) as their main source of cooking fat. In addition, the diet emphasized fruit, vegetables, non-refined grains and legumes; moderate to high consumption of fish; small to moderate intake of poultry and dairy products; low intake of red meat and processed meat; and avoidance of sugary drinks, fast food, and food rich in animal-based fat.
Participants received dietary advice at 18, 20, and 28 weeks’ gestation to help improve compliance and make sure the diet was made culturally sensitive. Investigators measured dietary compliance using self-reported feedback from the participants, so it’s important to note that there could have been human error in the reporting.
The investigators also assessed the effect of a Mediterranean diet on other pregnancy complications such as high blood pressure, preeclampsia, stillbirth, small for gestational age fetus, or admission to a neonatal care unit, but did not find any significant associations.
One in four mothers enter pregnancy with pre-existing obesity, chronic hypertension or raised lipid levels, which can lead to pregnancy complications, long-term risk of diabetes and cardiovascular complications for mothers and their children.(3,4,5) These findings provide additional support for following a Mediterranean-style diet which has been linked to additional health benefits such as improved cognitive function.
The California Walnut Commission (CWC) provided walnuts for this research. The CWC has supported health-related research on walnuts for more than 25 years with the intent to provide knowledge and understanding of the unique health benefits associated with consuming walnuts. While the CWC does provide funds and/or walnuts for various projects, all studies are conducted independently by researchers who design the experiments, interpret the results and present evidence-based conclusions. The CWC is committed to scientific integrity of industry-funded research.
The California walnut industry is made up of over 4,800 growers and over 90 handlers (processors). The growers and handlers are represented by two entities, the California Walnut Board (CWB) and the California Walnut Commission (CWC).
California Walnut Commission
The California Walnut Commission, established in 1987, is funded by mandatory assessments of the growers. The CWC represents over 4,800 growers and over 90 handlers (processors) of California walnuts in export market development activities and conducts health research. The CWC is an agency of the State of California that works in concurrence with the Secretary of the California Department of Food and Agriculture (CDFA).
The California Walnut Board (CWB) and California Walnut Commission (CWC) prohibit discrimination in all programs and activities on the basis of race, color, national origin, age, disability, sex, marital/familial/parental status, religion, sexual orientation, political beliefs, reprisal or retaliation for prior civil rights activity, or because all or part of an individual’s income is derived from any public assistance programs.
Persons with limited English proficiency or disabilities who require alternative means for communication of program information (translated materials, braille, large print, audiotape, etc.) should contact the CWB / CWC offices at (916) 932-7070.
To file a complaint of discrimination, complete the USDA Program Discrimination Complaint Form, AD-3027, found online at http://www.
1. H. Al Wattar B, Dodds J, Placzek A, Beresford L, Spyreli E, Moore A, et al. (2019) Mediterranean-style diet in pregnant women with metabolic risk factors (ESTEEM): A pragmatic multicentre randomised trial. PLoS Med 16(7): e1002857. https:/
2. Estruch R, Ros E, Salas-Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N Engl J Med. 2018;378(25):e34. doi: 10.1056/NEJMoa1800389.
3. Galtier-Dereure F, Boegner C, Bringer J. Obesity and pregnancy: complications and cost. Am J Clin Nutr. 2000;71(5):1242s-1248s.
4. The Public Health England Obesity website [Internet]. Available from: https:/
5. Osterman MJK, Martin JA, Curtin SC, et al. Newly released data from the revised U.S. birth certificate, 2011. National Vital Statistics Report 62(4), 2013. Hyattsville, MD: National Center for Health Statistics.
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