Pregnant women are underrepresented or absent in nutrition reference value studies
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Studies used to determine nutritional recommendations in the U.S. and Canada often lack women, including those who are pregnant, according to findings published in Science Advances.
“Our study points to gaps in knowledge about the exact level of micronutrients we need to eat to protect the health of women, including pregnant women,” Emily R. Smith, ScD, MPH, an assistant professor of exercise and nutrition science at George Washington University, said in a press release. “Our research is the first comprehensive review of the underlying research that informs nutrient reference values. These are used for so many things: from developing federal food programs to deciding what’s in your granola bar to determining the makeup of your prenatal vitamins.”
Smith and colleagues evaluated the evidence behind the nutrient reference values (NRVs) of 23 micronutrients. Specifically, they analyzed the studies’ populations and methods used to develop NRVs. Overall, the researchers reviewed 704 primary research studies employed in Dietary Reference Intakes, of which 60.2% were conducted in the U.S.
Among the 704 studies, 95.3% were conducted with human participants. Of those, 77.5% included women, 17.4% included pregnant or lactating women and 16.5% included men only.
In the studies that reported sex, women accounted for 28.9% of the participants, according to Smith and colleagues. Among the 26.8% of the studies that were randomized controlled trials, 78.3% included women, 17.5% included pregnant or lactating women and 11.1% included men only.
The researchers found that recommendation reports for 16 of the 23 micronutrients drew from studies that included no pregnant or lactating women. Most of the values for pregnancy were set by modifying the values for women who were not pregnant, and some values for women were derived from the values set for men, according to Smith and colleagues. They also observed that less than one-third of the studies reported the race or ethnicity of study participants. In the U.S.-based studies analyzed, 32% reported race or ethnicity, while 91.7% of all human studies’ participants had an unknown or unspecified race and ethnicity.
“Women and pregnant people have historically been underrepresented in biomedical research. We confirmed that this problem extends to the basic and translational research informing NRVs, which are very important in the nutrition field,” study coauthor Siran He, PhD, a postdoctoral scientist in global health and nutrition at George Washington University, told Healio Primary Care. “Therefore, through this work, we would like to showcase the urgent need for funders and researchers to address these fundamental gaps in knowledge, through funding, designing, conducting and evaluating high-quality nutrition research.”
He advised that primary care physicians and other clinical staff should not change the NRVs recommended to patients until additional research is completed.
References:
New study suggests women and pregnant people are underrepresented in research to inform nutrition reference values. https://mediarelations.gwu.edu/new-study-suggests-women-and-pregnant-people-are-underrepresented-research-inform-nutrition. Published Oct. 22, 2021. Accessed Oct. 28, 2021.
Smith ER, et al. Science Advances. 2021;doi:10.1126/sciadv.abj8016.
Perspective
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Andrew A. Bremer, MD, PhD, MAS
Women and pregnant people have historically been underrepresented in research. Pregnant people in particular have been considered a vulnerable population. However, we now appreciate the need to protect pregnant people through research rather than from research. Given the physiological adaptations that occur over the course of pregnancy, research involving pregnant people is paramount to specifically study any drugs, xenobiotics or supplements that are taken during pregnancy. The same is true for the study of nutrition during pregnancy, especially given the emerging science demonstrating the long-term impacts of maternal diet and nutritional status on maternal health, fetal health and the offspring’s health. However, since most of the studies to date that have been used to inform nutrient reference values and dietary reference intakes in the general population excluded pregnant people (and many excluded women), there is currently a fundamental gap in our basic understanding of micronutrient requirements over the course of pregnancy. Now that the gap is recognized, my hope is that investigators in the nutrition science field will fill the gap by considering sex as a biological variable and by including women and pregnant people in new research studies aimed at establishing relevant nutrient reference values. The time is now, and it is in the best interest of public health.
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