Effects of monitoring dietary biomarkers and providing vegetable juice on metabolic syndrome components in adults with an overweight or obese body mass index in Ulaanbaatar: a randomized controlled trial

Abstract

Background: Mongolian people have traditionally had poor vegetable intake habits, which is a cause of increasing prevalence of metabolic syndrome. Monitoring vegetable intake through the dietary biomarkers such as skin carotenoid level, and urinary sodium-to-potassium (Na/K) ratio (represents intake status of salt and vegetable), has been recently suggested to be useful to improve dietary habits. Vegetable juices are an easy way to consume vegetable-derived ingredients. This study aimed to examine the following two points in adults with an overweight or obese body mass index (BMI) in Ulaanbaatar; (1) relationships between these dietary biomarkers and metabolic syndrome components, and (2) effects of an intervention combining regular monitoring of these dietary biomarkers and provision of vegetable juices on values of the dietary biomarkers and metabolic syndrome components.

Methods: Ninety-four Mongolian adults with BMI ≥ 25 living in Ulaanbaatar were analyzed. (1) Relationships between baseline values of dietary biomarkers and metabolic syndrome components were analyzed by simple correlation and multiple regression analyses. (2) Participants were randomly allocated to control, monitoring, and monitoring + vegetable juice groups. During the 8-week intervention, the monitoring and monitoring + vegetable juice groups were monitored their dietary biomarkers and blood pressure every two weeks, and the monitoring + vegetable juice group was additionally provided with vegetable juice every day. Changes in dietary biomarkers and metabolic syndrome components before and after intervention were compared among the three groups.

Results: (1) The skin carotenoid levels were negatively correlated with blood triglyceride levels, whereas the urinary Na/K ratio was positively associated with systolic and diastolic blood pressure. (2) Through the intervention, the monitoring + vegetable juice group showed significant increase in skin carotenoid level (+ 1.72), decrease in urinary Na/K ratio (- 0.80 mol/mol), and decrease in waist circumference (- 2.63 cm) compared to the control group (+ 0.28, + 0.45, and + 0.22, respectively).

Conclusions: The combination of the monitoring dietary biomarkers and providing vegetable juice was suggested to be effective in improving dietary habits and metabolic syndrome components including waist circumference in Mongolian adults with an overweight or obese BMI.

Trial registration: UMIN-CTR Clinical Trial UMIN000051715 on July 26, 2023.

Keywords: Carotenoid; Dietary biomarkers; Dietary guidance; Dietary habit; Metabolic syndrome; Obesity; Urinary sodium-to-potassium ratio; Vegetable intake; Vegetable juice; Waist circumference.

Fig. 1

Flow diagram for the participant selection

Fig. 2

Relationships between dietary biomarkers and metabolic syndrome components. a Correlations between dietary biomarkers and metabolic syndrome components (Pearson’s correlation coefficient with P-value are shown; **P < 0.01, *P < 0.05). b Comparison of the triglyceride levels between the skin carotenoid level low group (skin carotenoid level ≤ 3.5, n = 47) and skin carotenoid level high group (> 3.5 skin carotenoid level, n = 46). c, d Comparison of the systolic and diastolic blood pressure between the urinary Na/K low group (Na/K ≤ 2.0, n = 24) and Na/K high group (> 2.0 Na/K, n = 69). Data are shown as the mean ± SD. The P-value was by Welch’s t-test. BMI: Body mass index. Urinary Na/K ratio: Urinary sodium-to-potassium ratio. SBP: Systolic blood pressure. DBP: Diastolic blood pressure. TC: Total cholesterol. LDL: Low-density lipoprotein cholesterol. HDL: High-density lipoprotein cholesterol. TG: Triglyceride. HbA1c: Hemoglobin A1c