A healthy diet rich in fibre is generally recommended, but new research shows it could be even more important during pregnancy to promote the wellbeing of the mother and child.
Plant-based fibre is broken down in the gut by bacteria into factors that influence the immune system.
Researchers from the University of Sydney’s Charles Perkins Centre, the Barwon Infant Study from Deakin University, Monash University, James Cook University and the Australian National University collaborated to investigate the role of these metabolic products of gut bacteria during pregnancy.
Senior author of the study Professor Ralph Nanan said the simple recommendation to ‘eat real food, mostly plants, and not too much’ might be the most effective primary prevention strategy for some of the most serious conditions of our time.
“The mother’s gut bacteria and diet appear to be crucial to promoting a healthy pregnancy,” Professor Nanan, from the University of Sydney School of Medicine and Charles Perkins Centre, said.
Published today in Nature Communications, the study found that in humans, reduced levels of acetate, which is mainly produced by fibre fermentation in the gut, is associated with the common and serious pregnancy-related condition preeclampsia.
Preeclampsia occurs in up to 10 percent of pregnancies and is characterised by high blood pressure, protein in the urine and severe swelling in the mother.
It also interferes with the child’s immune development whilst in the womb, with some evidence suggesting a link to higher rates of allergies and autoimmune disease later in life.
The current study found that preeclampsia affected the development of an important fetal immune organ, the thymus, which sits just behind the breastbone.
Fetuses in preeclamptic pregnancies were found to have a much smaller thymus than children from healthy pregnancies.
The cells the thymus normally generates, called T cells (thymus-derived cells) – specifically those associated with the prevention of allergies and autoimmune conditions such as diabetes – also remained lower in infants after preeclampsia, even four years after delivery.
The mechanisms of acetate on the developing fetal immune system were further examined in separate experiments involving mice that showed acetate was central in driving fetal thymus and T cell development.
Together, these results showed that promoting specific metabolic products of gut bacteria during pregnancy might be an effective way to maintain a healthy pregnancy and to prevent allergies and autoimmune conditions later in life.
They may also, in part, explain the rapid increase of allergies and autoimmune conditions as Western diets are increasingly dominated by highly processed foods, which are very low in fibre.
“More studies are urgently needed to understand how we can best target this system to reduce the growing burden of immune related diseases in the modern world,” said co-author Peter Vuillermin, co-lead of the Barwon Infant Study, a major birth cohort study being conducted by the Child Health Research Unit at Barwon Health in collaboration with the Murdoch Children’s Research Institute (MCRI) and Deakin University.
A healthy, balanced diet during pregnancy is essential to support optimal growth and development of the fetus and the physiological changes that occur in the mother. Fundamental aspects of healthy dietary behaviors during pregnancy include consuming foods that contain optimal amounts of energy as well as macro and micronutrients, achieving appropriate weight gain, adhering to general and pregnancy-specific food safety recommendations, and avoiding ingestion of harmful substances [1,2]. Previous studies have shown that if such behaviors are not adopted, there is an increased risk of adverse pregnancy outcomes including low birth weight , preeclampsia , pre-term birth , and neurodevelopmental problems such as fetal alcohol spectrum disorder .
Health Canada and The Public Health Agency of Canada provide several dietary recommendations to help women meet their increased caloric and nutrient needs (Table 1). Additional recommendations include increasing water intake and avoiding foods associated with food-borne illnesses such as undercooked fish and meat, raw eggs, unpasteurized products, and raw sprouts [2,7,8]. Although these guidelines exist to help women select a healthy diet, the extent to which women change their diets to meet pregnancy-related guidelines is unknown.
Dietary recommendations for pregnancy.
|EWCFG 1||Add 2–3 servings from any food group during the second and third trimester in addition to the daily recommendation 1,2,3|
|Vegetables and Fruit||7–8 servings|
|Grain Products||6–7 servings|
|Milk and Alternatives||2 servings|
|Meat and Alternatives||2 servings|
|Cooked fish||150 g/week 1|
|Calcium||1000 mg before and during pregnancy 3|
|Iron||18 mg before pregnancy; 27 mg during pregnancy 3|
|Folic acid||400 μg before pregnancy; 600 μg during pregnancy 3|
|Caffeine||Maximum 300 mg/day 3|
|Alcohol||No alcohol 3|
During pregnancy, motivation for eating a healthy diet may change relative to the non-pregnant state as women prepare for motherhood and consider the impact of their dietary intake on the baby’s health .
Personal values and beliefs about nutrition in pregnancy, advice from health professionals, and physical and physiological changes may interact with determinants of eating behaviors present in the non-pregnant state (e.g., personal preferences, time, money) to change diet-related behaviors [11,12,13].
Although most women are aware that healthy eating is important during pregnancy, women may lack knowledge of specific dietary recommendations or may not have the skills required to improve their diet .
Healthy eating may also be challenging during pregnancy as women face barriers such as food aversions, cravings, nausea, vomiting, tiredness, constipation, hemorrhoids, and heartburn .
Women may receive and follow advice from a variety of sources, including health professionals, peers, and educational resources, which influences their choices during pregnancy .
Understanding factors that motivate or deter pregnant women from making dietary changes is important for devising appropriate means to promote healthy eating behaviors in this population.
Therefore, the objectives of this study were to: (1) describe the dietary changes women report making during pregnancy; (2) describe why women made these dietary changes; and (3) determine what changes women make that align with prenatal nutrition recommendations and what motivates them to make these changes.
More information:Nature Communications (2019). DOI: 10.1038/s41467-019-10703-1
Journal information: Nature Communications
Provided by University of Sydney