N° 45 | May 2010

Vegetable and fruit consumption and reduced risk of preeclampsia

Background

Preeclampsia is a major cause of maternal and fetal morbidity and mortality, but the origin is unknown. Several dietary substances have been hypothesized to influence the risk of preeclampsia. The present study aimed to investigate the relationship between dietary patterns and the risk of developing preeclampsia in a large population of women who have never given birth.

Dietary patterns among pregnant women

The study was conducted in pregnant women in the Norwegian Mother and Child Cohort Study (MoBa). Participating women answered questionnaires at gestational weeks 15 (a general health questionnaire) and at weeks 17 to 22 (a food frequency questionnaire). The pregnancy outcomes were obtained from the Medical Birth Registry of Norway. Exploratory factor analysis was used to identify underlying patterns in the dietary data. We identified four dietary patterns. Each participant was assigned a score for each of the four patterns.

The first pattern, which was denoted the “vegetable pattern”, was characterized by high consumption of both fresh and cooked vegetables, cooking oil, olive oil, fruits and berries, rice, poultry and drinking water. The second pattern, which was denoted the “processed pattern” was characterized by high consumption of processed meat products, white bread, French fries, salty snacks and sugar-sweetened drinks. The “vegetable” factor scores increased with maternal age, length of education and height. The “vegetable” factor scores decreased with BMI and were higher in non-smokers than smokers. In comparison the “processed foods” factor scores decreased with increasing age, length of education and height, and increased with BMI and smoking. The other two patterns were not associated with maternal characteristics or with preeclampsia.

Associations between dietary patterns and preeclampsia

Among 23,423 women (who have never given birth), 1,267 (5.4%) developed preeclampsia. Women with preeclampsia had lower “vegetable” pattern scores and higher “processed food” pattern scores than those who did not develop preeclampsia (p<0.001). When adjusting for confounders the results showed that women with high scores on the vegetable pattern had significantly reduced risk of preeclampsia [relative risk (OR) for tertile (T) 3 versus T1: 0.72; 95% CI: 0.62, 0.85], and women with high scores on the processed food pattern had increased risk [OR for T3 versus T1: 1.21; 95% CI: 1.03, 1.42]. The effects of the patterns were also examined according to different combinations of factor scores (tertiles). The effect of having high scores on the vegetable pattern were strongest within the lowest tertile of the processed food pattern (35-40% risk reduction), while having high scores on the processed food pattern did not significantly increase the risk in any of the vegetable pattern tertiles.

Implications

Several mechanisms for a biological effect of dietary factors on the risk of preeclampsia may exist. The risk factors for preeclampsia include obesity, dyslipidemia, insulin resistance and other risk factors for atherosclerosis. Vegetables and plant foods are rich in micronutrients such as phytochemicals, antioxidants, vitamins and minerals and dietary fibre, whereas many processed foods are made with the addition of sugar, salt and saturated fats. In non-pregnant populations, dietary patterns characterized by high consumption of Fruit and Vegetables (F&V), and low consumption of processed meats and foods rich in sugar and fats have been shown to reduce markers of the metabolic syndrome, inflammation and cardiovascular disease.

The results of our study suggest that adherence to dietary advice to consume a diet abundant in F&V may also be beneficial with regard to preeclampsia. Pregnancy is a period when most women are highly motivated for dietary advice as changes towards a healthier diet may also benefit their children. Dietary changes are low cost and low risk compared to medical interventions and even a moderate increase in the intake of vegetables and plant foods may be of public health importance.

Brantsæter AL Haugen M, Samuelsen SO, Torjusen H, Trogstad L, Alexander J, Magnus P, Meltzer HM. A dietary pattern characterized by high intake of
vegetables, fruits, and vegetable oils is associated with reduced risk of preeclampsia in nulliparous pregnant Norwegian women. J Nutr. 2009
Jun;139:1162-8.

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