A new NHANES analysis suggests that the quality of plant foods may matter more than avoiding animal foods when it comes to cardiometabolic health during pregnancy.
Study: Plant-based diet quality and cardiometabolic biomarkers in pregnant U.S. women. Image Credit: Natalia Deriabina / Shutterstock
In a recent study published in the journal Nutrition and Health, researchers evaluated associations between plant-based diets and biomarkers of cardiometabolic health in pregnant women in the United States.
Plant-Based Pregnancy Diet Background
Plant-based diets are linked to cardiometabolic benefits, including a lower risk of hypertension, cardiovascular disease, and type 2 diabetes (T2D). The 2025 Dietary Guidelines Advisory Committee report recommends increasing consumption of plant-based whole foods and reducing intake of processed and red meat. Despite the evidence that healthful plant-based diets promote cardiometabolic health, research on these associations in pregnant women remains limited.
NHANES Pregnancy Diet Study Design
In the present study, researchers assessed associations between various indices of plant-based diet quality and biomarkers of cardiometabolic health among pregnant women in the United States (U.S.). Data were used from seven cycles of the National Health and Nutrition Examination Survey (NHANES) conducted from 2005 to 2020, prior to the pandemic. Pregnant women were identified through self-reports and urine pregnancy testing. Individuals who self-reported hypercholesterolemia, hypertension, or T2D, or were taking medications for these conditions, were excluded.
Demographic information was self-reported by survey respondents. Data on the types and amounts of food consumed were obtained through a first-day 24-hour dietary recall. The researchers calculated four known indices: total plant-based foods (All PBF), Healthy PBF, the overall (PDI) plant-based diet index, and the healthful (hPDI) plant-based diet index. In PDI, plant foods were assigned positive scores, while animal foods were assigned negative scores.
The hPDI additionally differentiated between unhealthy and healthy plant-based foods, assigning them positive and negative scores, respectively. All PBF included only fruits, legumes, seeds and nuts, grains, oils, vegetables, and added sugars, while the similar Healthy PBF index excluded added sugars, refined grains, oils, and fruit juice. In addition, the team modified two indices and developed Modified Healthy PBF and Modified All PBF.
Modified All PBF, which was similar to All PBF, excluded added sugars. Likewise, Modified Healthy PBF was comparable to Healthy PBF but included plant oils and excluded white potatoes. Biomarkers of cardiometabolic health included the homeostatic model assessment for insulin resistance (HOMA-IR), total cholesterol, insulin, fasting glucose, triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), TG/HDL-C ratio, and low-density lipoprotein cholesterol (LDL-C).
Normality of biomarkers was assessed using the Shapiro-Wilk test. Multivariable log-linear regression was used to explore associations between the six plant-based diet quality indices and biomarkers of cardiometabolic health. The plant-based diet quality indices were analyzed as tertiles and continuous variables. Analyses were adjusted for age, education, ethnicity/race, and the family income-to-poverty threshold ratio.
Cardiometabolic Biomarker Findings
Of the 761 pregnant women screened, 580 with both dietary and biomarker data available were included. When examined as continuous variables, all six indices showed positive association with HDL-C levels and negative association with the TG/HDL-C ratio. Further, higher scores on Healthy PBF, Modified Healthy PBF, and hPDI were all associated with lower HOMA-IR and insulin levels.
Modified Healthy PBF and hPDI were also negatively associated with TG levels. When analyzed as tertiles, the highest tertile of hPDI was associated with lower HOMA-IR and insulin levels than the lowest tertile. The highest tertile of Modified Healthy PBF was associated with higher HDL-C levels and lower HOMA-IR and insulin levels. The highest tertile of Healthy PBF was associated with higher HDL-C and lower fasting glucose, TG, and TG/HDL-C ratio.
Pregnancy Nutrition and Metabolic Health Implications
Together, the study explored the associations of six plant-based diet quality indices with biomarkers of cardiometabolic health in pregnant U.S. women. Higher scores across all indices were associated with some more favorable cardiometabolic biomarkers, particularly higher HDL-C and lower TG/HDL-C ratio. The associations were strongest and broadest for indices that emphasized the quality of plant-based foods and did not penalize animal foods, suggesting that the quality of plant foods may be more crucial than limiting animal foods during pregnancy. However, the cross-sectional analysis cannot establish causality, and the authors noted limitations, including reliance on a single 24-hour dietary recall, possible residual confounding, and the inability to adjust for pregnancy stage.
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