Preeclampsia, a multisystem syndrome of pregnancy, affects 3%-5% of pregnant women worldwide and is associated with adverse maternal and fetal outcomes, including maternal and/or fetal death. Other than early delivery of the fetus, there is no cure for pre-eclampsia. Pathways that influence the development of pre-eclampsia include genetic, epigenetic, lifestyle and environmental factors. Since diet or dietary supplements may affect the risk, this article assesses the relationship between nutrition and pre-eclampsia and develops a set of nutritional guidelines to reduce the risk of pre-eclampsia in pregnancy, this being of particular importance for those at high risk.
Understanding Preeclampsia
Preeclampsia is a pregnancy complication characterized by new-onset hypertension, proteinuria, and various end-organ dysfunctions, including the liver, brain, lung, and utero-placenta. It results from placental malperfusion followed by syncytiotrophoblast stress that releases soluble factors into the circulation causing an early imbalance between proangiogenic and antiangiogenic factors. Risk factors associated with PE include advanced maternal age, pre-pregnancy obesity, assisted reproductive technologies, and pre-existing conditions such as chronic hypertension and diabetes mellitus.
Preventing preeclampsia is essential for global health from the perspective of better maternal and neonatal health outcomes, economic benefits, and reduced healthcare burden.
Some examples of preeclampsia symptoms may include a headache that will not go away, changes in vision, nausea or vomiting, and swelling of the face or hands. Some have no symptoms, which is why it is important for pregnant women to visit their health care team regularly.
The Role of Diet and Nutrition
The association between the risk and progression of the pathophysiology of pre-eclampsia may explain the apparent benefit of dietary modifications. The clearest link between diet and pre-eclampsia is the effect of weight and gestational weight gain (GWG) on risk.
Read also: Nutritional Guidelines for Preeclampsia
Weight Management
Pre-pregnancy body mass index (BMI) is positively associated with the risk of pre-eclampsia. Body mass index is proportionally correlated with pre-eclampsia risk, therefore women should aim for a healthy pre-pregnancy body weight and avoid excessive gestational and interpregnancy weight gain. Interpregnancy weight gain has also been shown to increase the risk of pre-eclampsia and of recurrent pre-eclampsia; therefore, excessive weight gain during pregnancy and between pregnancies should be avoided. The aim is to maintain a healthy weight prior to conception. However, in women at risk of pre-eclampsia who are overweight and/or obese, dietary interventions to reduce excessive GWG may be beneficial both for the mother and the baby.
Dietary Patterns
Research suggests that diets characterised by higher intakes of fruits and/or vegetables reduce the risk of pre-eclampsia. Consuming ≥400 g/day of fruits and vegetables, plant-based foods and vegetable oils and a limited intake of foods high in fat, sugar and salt may be beneficial. For example, a Norwegian observational study assessed the diet of 23 000 mothers and found that a diet characterised by higher vegetables, plant foods and vegetable oils was associated with a reduced risk of pre-eclampsia (OR 0.72, 95% CI 0.62 to 0.85). Furthermore, a prospective study of over 30 000 nulliparous women found that intakes of fresh and dried fruits reduced the risk of pre-eclampsia.
Fiber Intake
Consuming a high-fibre diet (25-30 g/day) may attenuate dyslipidaemia and reduce blood pressure and inflammation. A 2005 case-control study assessed fibre intake in 172 women with pre-eclampsia and 339 controls using Food Frequency Questionnaires (FFQs). After adjusting for confounders, women in the highest quartile of fibre intake (>24.3 g/day) had a 51% reduced risk of developing pre-eclampsia (OR 0.49, 95% CI 0.24 to 1.00) than women in the lowest quartile of fibre intake (<13.1 g/day). Moreover, use of logistic regression procedures suggested that as total fibre intake increased to around 27-30 g/day, pre-eclampsia risk decreased. A high-fibre diet is recommended for pregnant women. They should aim for a dietary fibre intake of 25-30 g/day to reduce the risk of pre-eclampsia.
Probiotics
A protective association was seen in the use of milk-based probiotic products on pre-eclampsia risk, including severe pre-eclampsia, especially when consumed during late pregnancy. Pregnant women should therefore aim to incorporate dairy-based probiotics into their diet.
Key Nutrients and Supplements
Other key nutrients that may mitigate the risk include increased calcium intake, a daily multivitamin/mineral supplement and an adequate vitamin D status.
Read also: The Hoxsey Diet
Calcium
Low calcium intake decreases plasma calcium concentration leading to activation of the renin-angiotensin-aldosterone system (RAAS). The evidence suggests that increasing calcium intake in pregnancy may effectively reduce pre-eclampsia incidence, especially among populations at heightened risk. All pregnant women should be supplemented with 1 g calcium per day from 20 weeks’ gestation to delivery. Daily 500 mg calcium supplementation can roughly halve the risk of PE in settings where calcium intake is low, including in Japan.
Vitamin D
There is some controversy about the amount of vitamin D that is necessary for avoidance of deficiency and the required concentration of the serum vitamin D metabolite, 25(OH)D, for adequacy. When considering the evidence outlined, multiple studies suggest that the risk of pre-eclampsia was probably reduced with vitamin D supplementation. Vitamin D supplementation in pregnant women is frequently required to achieve sufficient status as recommended by vitamin D guidelines so pregnant women should take a daily vitamin D supplement of 10-25 µg (400-1000 IU) to ensure they are not deficient. This may reduce their risk of pre-eclampsia.
Selenium
For those with a low selenium intake (such as those living in Europe), fish/seafood intake could be increased to improve selenium intake or selenium could be supplemented in the recommended multivitamin/mineral supplement. A systematic review and meta-analysis was published in 2016 that looked at 13 studies with 1515 participants. It showed an inverse association of blood selenium level with the risk of pre-eclampsia and that supplementation with selenium significantly reduces the incidence of pre-eclampsia. Low selenium status may be a risk for pre-eclampsia in women with low selenium status though the level of status at which the risk increases is unclear.
Other Vitamins and Minerals
A recent meta-analysis of 19 studies looked at the serum vitamin B12 concentrations of women with pre-eclampsia and found that they were significantly lower than those of healthy pregnant women.
Vitamin C was not associated with an increased risk of any type of PE. Vitamin C showed an increased incidence of severe pre-eclampsia, eclampsia and HELLP.
Read also: Walnut Keto Guide
There was no association between magnesium supplementation and the risk of perinatal mortality or small for gestational age.
Dietary Supplements in Japan
Dietary supplements are products intended to supplement a diet and provide nutrients that may not be consumed in sufficient quantities through food. In Japan, dietary supplements are classified as “health foods” and further divided into Foods with Health Claims and other health foods.
Diets of Women of Reproductive Age and Pregnant Women in Japan
The diets of Japanese women of reproductive age, as well as pregnant women, are characterized by common issues such as inadequate energy intake and specific nutrient deficiencies. Key nutrients, such as calcium, iron, and vitamin D, are also consumed at inadequate levels in women aged 20-29 years, with an estimated shortage of 37-46% below recommended values.
The Importance of Preconception Care
The growing global emphasis on preconception care reflects its critical role in optimizing maternal and child health outcomes. Considering the current nutritional status of Japanese women, systematic reviews and meta-analyses to evaluate the efficacy of various dietary supplements, including vitamins (vitamins A, B6, C, D, and E, folic acid, and multivitamins), minerals (calcium, magnesium, zinc, and iron), amino acids (l-arginine and l-carnitine), anti-oxidants (lycopene, resveratrol, and astaxanthin), and other agents (omega-3 fatty acid, coenzyme Q10, melatonin, and s-equol), in preventing PE during pregnancy.
Nutrition and Physical Activity Recommendations
While managing preeclampsia is outside WIC's scope, managing high blood pressure that existed before pregnancy includes lifestyle changes consistent with general recommendations for a healthy pregnancy: eating a heart healthy diet, managing stress, and not smoking.
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