Introduction:
Previous evidence suggests that soy containing foods may have beneficial effects on lipid and glycemic metabolism due to their biologically active components, including soy protein and isoflavones. Pregnancy is associated with changes in glucose and lipid metabolism, partially attributable to elevated estrogen concentrations. We have previously reported a significant, inverse association between urinary excretion of isoflavones and cardiometabolic risk markers in pregnant women, using data from the National Health and Nutrition Examination Survey (NHANES). Further studies are needed to determine the cardiometabolic health effects of soy intake in pregnant women.
Hypothesis:
We hypothesize that consumption of soy-based whole foods is safe and acceptable for pregnant women and has beneficial cardiometabolic health effects.
Methods:
A pilot randomized controlled trial (RCT) was conducted in 30 pregnant women who received counseling to consume either a high-soy or low-soy foods containing diet. Assessments (physical and anthropometric measurements, food frequency questionnaires, fasting blood samples) were conducted at 14 and 28 weeks of pregnancy, and 6 weeks’ postpartum. Monthly follow-up calls were conducted by research team coordinator to assess safety and encourage adherence.
Results:
Both the high-soy and low-soy groups demonstrated high adherence (80-90%), defined as consuming soy foods ≥ 15 days in the past four weeks for high-soy group and ≤ 5 days for low-soy group. Five subjects in the high-soy group reported adverse events (nausea, vomiting, diarrhea, itchy mouth); all were transient and resolved without sequelae. No adverse events were reported in the low-soy group. Skinfold thickness decreased (-4.8 mm) in the high-soy group and increased (+3.6 mm) in the low-soy group (p=0.04). There was a trend towards lower BMI in the high-soy compared to low-soy group at 28 weeks (+1.4 vs. +3.6 kg/m
2
, respectively, p=0.15) and postpartum (-1.2 vs. +0.6 kg/m
2
, respectively, p=0.14). This decrease in BMI was predominantly a loss of body fat and not lean mass. There were no significant differences between groups in fasting glucose, HDL-C, LDL-C, TG, or VLDL concentrations.
Conclusions:
In conclusion, results from this pilot RCT support the acceptability and safety of consuming soy-based whole foods during pregnancy. A larger-scale RCT is needed to further elucidate the effects of soy-based foods on cardiometabolic risk factors during pregnancy, as well as the transgenerational effects on their offspring.
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