Can a healthy diet prevent preeclampsia in a woman who would otherwise develop it?

Evidence for Dietary Interventions in Preeclampsia Prevention

Calcium supplementation is the only dietary intervention with strong evidence for preeclampsia prevention in women with low calcium intake, while general healthy dietary patterns may provide additional benefits but lack definitive evidence for preventing preeclampsia.

Calcium Supplementation: The Most Evidence-Based Dietary Intervention

The WHO and multiple obstetric organizations strongly recommend calcium supplementation for preeclampsia prevention, particularly in women with low calcium intake:

• Women at increased risk for preeclampsia should receive supplemental calcium (1.2–2.5 g/day) if their intake is likely to be low (<600 mg/day) 1
• When calcium intake cannot be assessed or predicted, it is reasonable to give calcium supplementation 1
• The WHO recommends daily administration of 1.5–2.0 g of supplemental calcium from 20 weeks of gestation onwards 1
• Calcium carbonate is the most cost-effective formulation 1, 2

Other Dietary Approaches with Limited Evidence

While calcium supplementation has strong evidence, other dietary interventions show less conclusive results:

• Diets focusing on fruits, vegetables, whole grains, and limiting foods high in fat, sugar, and salt are associated with reduced preeclampsia risk 2, 3
• A high-fiber diet (25-30 g/day) may help reduce blood pressure and inflammation 3
• Consuming ≥400 g/day of fruits and vegetables may be beneficial 3
• Dark chocolate, flavonoid-rich foods, and long-chain polyunsaturated fatty acids have been studied but lack strong evidence 4

Weight Management and Preeclampsia Risk

Body weight plays an important role in preeclampsia risk:

• Body mass index is proportionally correlated with preeclampsia risk 3
• Women should aim for a healthy pre-pregnancy body weight 2, 3
• Avoiding excessive gestational and interpregnancy weight gain is recommended 2, 3
• Weight reduction during pregnancy is not recommended despite potential benefits in reducing blood pressure 2

Supplements That Lack Evidence for Preeclampsia Prevention

Several supplements previously thought to help prevent preeclampsia have been shown to be ineffective:

• Vitamins C and E supplementation is not recommended 3, 4
• Vitamin D supplementation lacks supporting evidence 4
• Magnesium supplementation has not shown benefit 3
• Salt restriction does not prevent preeclampsia 3
• Zinc or folic acid supplementation lacks strong evidence 4
• Omega-3 fatty acids (fish oils) have not demonstrated preventive effects 3

Recommended Approach for Preeclampsia Prevention

For women at risk of preeclampsia, the following approach is recommended:

1. Calcium supplementation: 1.2-2.0 g/day for women with low calcium intake or when intake cannot be assessed 1, 2
2. Low-dose aspirin: 75-162 mg/day before 16 weeks of gestation for women with established clinical risk factors 1, 2
3. Healthy diet: Emphasize fruits, vegetables, whole grains, and plant-based foods while limiting foods high in fat, sugar, and salt 2, 3
4. Weight management: Aim for healthy pre-pregnancy weight and avoid excessive weight gain 2, 3
5. Regular exercise: Maintain physical activity during pregnancy 1

Risk Factors for Preeclampsia

Women with these risk factors should be particularly vigilant about preventive measures:

• Prior preeclampsia
• Chronic hypertension
• Pregestational diabetes mellitus
• BMI >30 kg/m²
• Antiphospholipid syndrome
• Receipt of assisted reproduction 1
• Nulliparity
• Multiple pregnancies 5

Limitations and Caveats

• The exact pathophysiology of preeclampsia remains incompletely understood 6, 5
• The threshold of calcium intake below which supplementation becomes efficacious is unknown 1
• Timing of nutritional interventions is important - ideally beginning before or early in pregnancy 2
• Separating calcium and iron supplements by several hours may be beneficial to prevent reduced iron absorption, though clinical impact appears minimal 1, 2

While calcium supplementation has strong evidence for preeclampsia prevention in women with low calcium intake, the evidence for other dietary interventions remains limited. Healthcare providers should focus on implementing evidence-based recommendations, particularly calcium supplementation for at-risk women, while promoting overall healthy dietary patterns and weight management.