“How two slices of brown bread a day protects pregnant women against life threatening pre-eclampsia” is the headline in the Daily Mail . The newspaper discusses the results from a study of more than 1500 women, which suggests that eating a high-fibre diet protects against pre-eclampsia in pregnancy. The lead researcher, Dr Qiu, is quoted as saying that adding two slices of brown bread per day is the equivalent of adding 5g of fibre to the diet.
The researchers are cautious about the conclusions they draw from this study. However, they say that when considered alongside the results of other published studies, theirs suggests a link between intake of fibre in early pregnancy and reduced risk of pre-eclampsia. The design of this study means that it cannot provide concrete evidence that increasing fibre consumption reduces risk of pre-eclampsia. More research is needed to prove this conclusively. Pregnant women, and the population as a whole, should aim to eat a healthy balanced diet that is high in fibre.
Dr Chunfang Qiu and colleagues from the Swedish Medical Center in Washington, and the University of Washington School of Public Health and Community Medicine carried out this study. The research was funded by the National Institutes of Health. It was published in the peer-reviewed medical journal, the American Journal of Hypertension .
This is a cohort study where researchers were interested in the link between maternal dietary fibre and pre-eclampsia. The participants were women from the Omega Study, where 1,538 women agreed to participate in an investigation of diet and pre-eclampsia between 1996 and 2002. Those with chronic high blood pressure and/or diabetes mellitus were excluded, as were those with missing information on fibre intake. Of these 1,538 women, 64 were diagnosed with pre-eclampsia (sustained high blood pressure during pregnancy with evidence of protein in urine). In a separate analysis, the researchers included another 46 women who met slightly different criteria for pre-eclampsia (according to newer screening criteria).
The women were given food frequency questionnaires at around 13.1 weeks of pregnancy to assess their diet before conception and during the first trimester. From this, researchers were able to determine total dietary fibre intake, and intake of other nutrients including vitamin C, fats and carbohydrates. The level of fats (lipids) in the women’s blood was determined through blood samples collected at 13.1 weeks’ gestation.
The researchers also collected demographic information about the women, including education, ethnicity, number of children, smoking and body mass index (BMI). Intake of fibre was categorised into quartiles (the participants were divided into four groups according to their intake, from low to high, with each group containing 25% of the participants). Risk of pre-eclampsia across these quartiles was then compared.
The researchers found that total fibre intake was associated with risk of pre-eclampsia, with women in the highest quartile of intake (reporting more than 21g of fibre per day) experiencing a 66%-72% reduced risk compared with those in the lowest quartile of intake. This difference remained even after accounting for factors such as energy intake, maternal age, ethnicity, BMI, vitamin C and parity. They also found that women with the highest fibre intake had the lowest levels of blood triglycerides (excess fat) and higher levels of good cholesterol.
The researchers conclude that their results, when taken together with previously published studies, suggest important health benefits associated with increased fibre consumption before and during early pregnancy. They say that if their findings are confirmed by other studies, this “may motivate increased efforts aimed at exploring lifestyle approaches, particularly dietary approaches, to lower the risk of pre-eclampsia”.
The researchers raise important limitations associated with their study:
The researchers call for more studies of pregnant women “to demonstrate these potential causal relationships more conclusively”.