A diet based mainly on foods of plant origin was associated with a lower risk of developing hypertensive disorders of pregnancy, according to the results of research published in American Journal of Obstetrics and Gynecology.[1]
The prospective cohort study followed 11,459 women over 18 years (1991-2009) and assessed diet from baseline using a validated plant-based food frequency and quality questionnaire. This tool allowed us to calculate the plant-based diet index (plant-based diet index-PDI) even among omnivorous participants. A higher score indicates greater adherence to the PDI.
Dr. Jorge E. Chavarro
“We wanted to know how previous diet influences pregnancy, so we followed the women practically for their entire reproductive life, almost 20 years, knowing their usual diet before pregnancy,” he told Medscape in Spanish the leading doctor of the work, Dr. Jorge E. Chavarro, professor of nutrition, epidemiology and medicine at the Schools of Public Health and Medicine of Harvard University, in Harvard, United States, and his research area is studying how nutrition and lifestyle influences reproductive health and the general health of women throughout life.
The analysis of the data from the Nurses’ Health Study II made it possible to detect that as the proportion of products changed, the proportion of animals decreased and that of vegetables increased, and the risk of women having hypertensive disorders of pregnancy also decreased. Women in the highest quintile of PDI were significantly associated with a lower risk of hypertensive disorders of pregnancy compared to those in the lowest quintile (relative risk [RR]: 0.76; 95% confidence interval [IC 95%]: 0.62 to 0.93]). This association was slightly stronger for pregnancy-induced hypertensive disease (RR: 0.77; 95% CI: 0.60 to 0.99) than for preeclampsia (RR: 0.80; 95% CI: 0. 61 to 1.04).
Women in the highest quintile of PDI had a 24% lower risk of hypertensive disorders of pregnancy than those in the lowest quintile; the risk of pregnancy-induced hypertensive disease decreased in a linear pattern with increasing PDI, while the relationship of PDI with preeclampsia was restricted to women in the highest quintile of adherence.
“It was clearer for pregnancy hypertension than for preeclampsia, but the diet based mainly on plant foods seemed to be protective for both,” Dr. Chavarro said, adding that in addition to the problems they generate in pregnancy, both increase the risk of suffering from other chronic diseases later. “Could it be that modifiable lifestyle factors both before and during pregnancy can not only help reduce problems during pregnancy, but also prevent women’s health problems years later? That was the general motivation of the study.”
Mercedes Sotos-Prieto, Ph.D.
Mercedes Sotos-Prieto, Ph. D., who was not involved in the study, told Medscape in Spanish that the methodology is very robust, with appropriate statistical techniques for what it analyzes and highlights that it uses a validated food consumption frequency questionnaire. He considers the study important, also for focusing on that population group. “There has always been greater reluctance with the diet of pregnant women, as with that of older adults. But it has been seen that this type of diet, if it is of quality, could be associated with health benefits.”
Sotos-Prieto, doctor in nutritional epidemiology and public health, researcher at the Autonomous University of Madrid and associate professor at the Harvard University School of Public Health, works with large epidemiological cohorts, such as that of American nurses on which it is based this article and ENRICA, representative of the Spanish population and elderly adults. She is the author of other studies that, like this one, associated a diet based on healthy plant-based foods with a lower risk of frailty both in the Nurses’ Health Study in the United States and in a study of ≥60 years of age in Spain (ENRICA -1).[2,3]
Likewise, she is the principal investigator of a project to assess the risk of cardiovascular disease based on modifiable lifestyles that created a tool: Healthy Heart Test, to evaluate the quality of the diet “in five minutes, because we know that doctors do not they have time”. She considers it a type of test that could be implemented in clinical practice to identify lifestyle behaviors that can be improved, for example, substituting whole grains for refined grains or increasing legume consumption.
Nobody disputes that tomatoes are healthy, but what about French fries?
Most of the benefit is derived from the plant-based diet pattern as a whole and not from the individual association of any food. But these studies use a score of what is and isn’t healthy.
Diet was assessed every four years (beginning in 1991) using a semiquantitative food frequency questionnaire (FFQ) that recorded consumption of 131 foods and beverages during the previous year, in terms of how often, on average, the participants consumed each food. 18 food groups were assigned into three categories: healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, vegetable oils, tea and coffee), unhealthy plant foods (fruit juices, refined grains, potatoes, sugary drinks, sweets and desserts) and foods of animal origin (dairy, eggs, fish or shellfish, meat and various foods of animal origin.)
Healthy plant foods were converted to positive scores, while less healthy vegetables and animal food groups were converted to reverse scores. Intake of each food group was classified into PDI using quintiles.
Women in the highest quintile of PDI were significantly associated with a lower risk of hypertensive disorders of pregnancy compared to women in the lowest quintile. There was an inverse dose-response relationship between PDI and disease risk. “A vegetarian diet does not have to be healthier than a non-vegetarian one if it is based on superfluous foods such as chips and soft drinks, highlighted Dr. Sotos-Prieto. The difference lies in the quality of plant-based foods, there There is the difference between healthy and unhealthy.
Is it necessary to abandon meat?
Dr. Chavarro noted that giving up meat for dinner was one of the most difficult things 22 years ago. “Now I do it without a problem,” he said. But he understands that there are people for whom making a diet change by replacing animal products with non-animal products is difficult. However, it is not about abandoning meat permanently.
“In the highest quintile, women are not vegetarian or vegan either, but they eat much less food of animal origin than the others,” she pointed out, adding that vegetarian or vegan diets are not incompatible with a healthy pregnancy. “All vegans know how to find vitamin B12 in supplements”.
Is it diet or weight loss?
Much of the benefit seen in the study appears to be related to better weight control.
Body mass index between dietary assessment and pregnancy explained 39% of the relationship between PDI and hypertensive disorders of pregnancy, and 48% of the relationship between PDI and pregnancy-induced hypertensive disease.
“Part of the association appears to be explained by better weight control over long periods,” Dr. Chavarro explained. Women who adopted the diet with more foods of plant origin gained weight more slowly than those who consumed more foods of animal origin. “They are differences due to weight trajectories over many years, so part of the association we see has to do with better long-term weight control, but the other half of the association is attributable to diet per se and not necessarily to weight.” In the discussion of the article, the authors suggest to explain mechanisms of action in endothelial dysfunction, inflammation or blood pressure before pregnancy.
Sotos-Prieto considers this point “really relevant.” In her opinion, it shows that for the population of pregnant women it is very important to control weight at the beginning of pregnancy, which can also improve other factors, such as gestational diabetes. “I think preventive measures should focus on that and based on these results it is evident that there must be interventions to increase the chances of starting a pregnancy with an adequate weight. And this includes dietary modification.”
Can it be extrapolated to other populations?
More than 90% of the Nurses’ Health Study participants were white, non-Hispanic. Can it be extrapolated to other populations? “The answer requires repeating the study in other populations,” admitted Dr. Chavarro, “and that will take time. But even without that information, I believe we can use it to inform other populations, regardless of ethnicity.”
The specialist admitted that this hypothesis has not yet been tested in the Spanish population, but she is the author of a similar study that followed almost 12,000 Spanish adults for a decade and used the same PDI. In their work, each ten-point increase in the PDI was associated with a 14% lower risk of mortality from all causes (HR: 0.86; 95% CI: 0.74 to 0.99) and a 37% lower risk of death due to cardiovascular disease (HR: 0.63; 95% CI: 0.46 to 0.85).[4] Likewise, he considers that the recommendations derived from the study could be generalized to other populations “as long as the culture of each country is taken into account, to see how it can be culturally adapted. If it is a population that has a high consumption of refined cereals , for example, making small changes to whole grains.
What is the weight of the evidence?
The study has strengths and limitations derived from the methodology and Dr. Chavarro himself recognizes that “in terms of hypertensive disorders of pregnancy specifically, this is not going to be the last word.” But the need to find answers is important.
As he American College of Obstetricians and Gynecologists (ACOG) and the World Health Organization (WHO) suggest that women follow healthy diets before and during pregnancy. But they provide little guidance on what constitutes a healthy diet when it comes to minimizing the risks of adverse pregnancy outcomes. “They are quite ambiguous and nonspecific,” Dr. Chavarro added.
The new findings indicate that plant-based diets may be one such strategy, particularly because some evidence was found that they may be beneficial in women over 35 years of age who are considered a high-risk group.
“There are undoubtedly many ways to eat healthily, but if we think about these pregnancy complications that can have serious consequences for both the mother and the fetus, we could think of this as one of the possible healthy diets,” highlighted the doctor. .
But how robust is the evidence to recommend patients make a change? “Ideally, more studies are needed,” stated Dr. Chavarro. “There are two ways to understand the problem. One is not to make recommendations until we have three controlled clinical trials, which even with will and financing will take 15 to 20 years. But we do have to give the best information there is to the people who need it today, I think these results are solid in guiding behavior.
“It is always better if we can make decisions based on solid and incontrovertible information, but it is not always available and you must learn to live in both worlds and make decisions with uncertainties,” he concluded.
Sotos-Prieto, Ph. D., and Dr. Chavarro have disclosed no relevant financial relationships.
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