Mediterranean-style diet could reduce preeclampsia risk by at least 20%

A new Johns Hopkins Medicine study that surveyed a racially diverse group of more than 8,000 women has added to evidence that following a Mediterranean-style diet could lower the risk of preeclampsia by at least 20%. Preeclampsia is a potentially lethal complication of pregnancy marked by high blood pressure and organ damage that emerges in late pregnancy or shortly after giving birth. Worldwide, it is a significant cause of maternal and fetal death and premature birth. In the United States, preeclampsia occurs in about 2%-6% of women, and twice as often in Black women compared with other racial groups.

A report on the new study, published April 20 in the Journal of the American Heart Association, found that women who self-reported eating a Mediterranean-style diet had a 20% or greater reduced risk of developing preeclampsia overall, even after accounting for a variety of other risk factors.

A Mediterranean diet largely consists of vegetables, fruits, fish, nuts, olive oil, whole grains and significantly limited amounts of red meats and processed foods. It has been linked for decades to reduced risk of cardiovascular disease.

The United States is the only developed country with a rise in maternal mortality and morbidity, so we are excited about this new finding that strengthens recommendations that following a healthy diet is a safe way to help reduce the risk of pregnancy complications."

Anum Minhas, M.D., M.H.S., chief cardiology fellow and lead author of the study

For the study, researchers surveyed 8,507 women enrolled in the Boston Birth Cohort study between 1999 and 2014, a project originally designed to investigate the genetic and environmental factors associated with premature births. Overall, 47% of study participants were Black, 28% were Hispanic and the remaining 25% were white or other races. The average age was 28 years old.

Participants were asked to complete a dietary survey within 24-72 hours after giving birth, with questions focused on how often Mediterranean-style foods were consumed throughout pregnancy. Based on the responses, participants were assigned a diet score and sorted into three groups for analysis and comparison. Higher scores reflected higher frequencies of Mediterranean food consumption.

A total of 10% of surveyed women (848) developed preeclampsia. After adjusting the groupings for age, race, education, marital status, smoking, previous pregnancies and obesity, investigators report that:

• Compared with women who scored in the lowest group, women who scored in the middle and highest groups had 28% and 22% lower risks of preeclampsia.
• Black women who followed the Mediterranean-style diet and scored in the highest group had a 26% reduced risk of preeclampsia compared with those who scored in the lowest group.
• Women entering pregnancy with chronic high blood pressure had nine times the risk of preeclampsia compared with women entering pregnancy without a previous history of hypertension.
• Women with preexisting diabetes and obesity had twice the risk of preeclampsia compared with women without these conditions.

In addition to a healthy diet's link to overall better pregnancy outcomes, the study, Minhas says, suggests that racial differences in rates of preeclampsia in the U.S. might be more related to socioeconomic factors than genetic or biological ones since all racial groups benefited from the diet.

"While our findings strengthen the case that adherence to a healthy diet reduces pregnancy complications, clinical trials are still needed to precisely evaluate the benefits of the Mediterranean diet in diverse groups of pregnant women," cautions Noel Mueller, Ph.D., associate professor at the Johns Hopkins Bloomberg School of Public Health and senior author of the study.

"These new findings are exciting in context of other data showing that beyond pregnancy, a greater adherence to a Mediterranean-style diet is associated with reductions in blood pressure, improvement in blood lipids and lower risk of future cardiovascular events like heart attacks and strokes," adds Erin Michos, M.D., associate director of preventive cardiology at Johns Hopkins Medicine and co-author of this study. "Lifestyle is impactful -; one can change the trajectory of their health through following a healthy diet, combined with regular physical activity and not smoking."

Sharon Smith, Ph.D., an epidemiologist and program officer in the Division of Cardiovascular Sciences at the National Heart, Lung, and Blood Institute, part of the National Institutes of Health, agreed. "Results of this observational study suggest that a heart-healthy diet is associated with reduced blood pressure in pregnant women at high risk for preeclampsia," Smith said. "The findings in Black women are particularly encouraging because of their higher rates of preeclampsia and adverse outcomes compared with other groups. We look forward to future dietary studies that confirm these findings in an effort to reduce maternal mortality and health disparities associated with it."