Pre-eclampsia (PE), along with gestational diabetes mellitus (GDM), may increase the risk of maternal and foetal adverse outcomes but researchers suggest polyphenol intake during pregnancy could safeguard against disease progression through antioxidant activity.
Polyphenols found in chocolate, tea, fruit, berries, and other food products are naturally occurring compounds with recognised health benefits, such as improving glucose tolerance and redox status, and reducing chronic low-grade inflammation and fatty liver, which inhibit disease pathogenesis.
“At a molecular level, both GDM and PE conditions share an imbalance in the prooxidant/antioxidant mechanisms. Many studies have suggested that the ingestion of extracts enriched in polyphenols or polyphenol-rich foods may exert positive effects in maternal and foetus health during pregnancy,” the authors of the recent meta-analysis write.
GDM and PE are common during pregnancy and associated with heightened risk of pregnancy-induced hypertension and PE. Meanwhile, GDM affects 6-25% of pregnant women, researchers explain.
“Hyperglycaemia during pregnancy is associated with an increased risk of suffering pregnancy complications but also impacts the development of the offspring.”
Moreover, women with GDM often have lower levels of circulating antioxidants, like selenium, zinc, vitamin E and total antioxidant capacity, than women with normal pregnancies.
In the case of PE, “pathological alterations are associated with oxidative and nitrosative free radical production by the placenta, which is considered to be one of the main molecular determinants of the disease during pregnancy”, they say.
Treating GDM is fundamental to prevent pregnancy complications and infant death, as well as to protect mother and child from the long-term consequences. Furthermore, there is no cure for PE, other than delivery, so managing is essential to reduce condition severity.
Researchers conducted a systematic review and meta-analysis of 12 studies on polyphenol consumption and pregnancy complications, of which eight focused on GDM risks and four on PE. Subjects had been recruited from hospitals, care practices or national cohort.
Two GDM studies concentrated on the effects of polyphenol intake from coffee, chocolate, and soy isoflavones food sources on a total cohort of 162,443 individuals. Results from all eight GDM studies were based on questionnaires or with in-person or telephone interviews.
Other polyphenol-rich foods covered in study data included tea, fruit, and berries. Total polyphenol, soy isoflavones, total flavonoids, and total anthocyanin intake were evaluated.
Studies that quantified total polyphenol intake or their sub-classes and those that assessed the association between polyphenol consumption and PE without gestational hypertension, were analysed separately.
Of the four studies that evaluated the relationship between polyphenol-rich food consumption during pregnancy and PE risk, one compared low versus higher consumption and three compared no consumption with high consumption.
No association was found between overall polyphenol consumption and the risk of GDM or PE in this meta-analysis. However, in subtypes analyses, a protective effect (RR = 0.78) was noted against GDM.
Paradoxically, sub-type analyses of 88,073 women in two studies revealed coffee or chocolate consumption did contribute to lower PE risk.
"This might imply a possible protective effect of these nutrients that warrants further study," the report states.
Despite strong evidence on the benefits of polyphenols on blood pressure that induces vasodilation (like resveratrol), their role in preventing pre-eclampsia is unknown, the authors comment.
Recent studies also demonstrate the positive effects of polyphenols in fruit and vegetables on glucose homeostasis through broad mechanistic activity (inhibition of digestive enzymes, reducing activation of glucose transporter in small intestinal epithelial cells, for example) that improve glucose tolerance.
The absence of positive effects in the meta-analysis may relate to the limited studies and the “in-between studies’ heterogenicity”, the authors assert. Pre-pregnancy polyphenol intake was another unknown variable that may have had an impact on findings.
Nevertheless, they stress the need to improve prevention strategies through lifestyle dietary changes and increased physical activity but add “whether polyphenols in particular have more benefit associated with lower risk is unknown/unclear.”
“Even if the clinical effects of polyphenols could be short term, it is expected that the benefits occur under a chronic consumption,” they add.
Published online, November 19, 2022: http://doi.org/10.3390/antixo11112294
"Association of Polyphenols Consumption with Risk for Gestational Diabetes Mellitus and Preeclampsia: A Systematic Review and Meta-Analysis"
Authors: Jorquera, G., Fornes, R., Cruz, G., and Thomas-Valdés, S.