Increasing Consumption of Vegetables Decreases Acid Excretion and Bone Turnover Among Adults with Overweight and Obesity: An 8-Wk Randomized Controlled Trial

Abstract

Abstract Objectives To investigate the extent to which increased vegetable consumption affects urinary acid excretion and serum bone markers. Epidemiological studies suggest vegetable intake is positively associated with bone health through several mechanisms such as reducing oxidative stress and inflammation or diet-induced metabolic acidosis. We hypothesized that increasing intake of vegetables to the amounts and types recommended by the Dietary Guidelines for Americans (DGA) is beneficial to bone health by suppressing bone turnover. Methods One-hundred and ten adults with overweight or obesity were recruited in a two-arm, parallel-designed, randomized controlled community-based 8-wk feeding intervention trial. The two arms included (1) attention control arm, and (2) active intervention arm during which participants received a variety of pre-packaged, minimally prepared fresh or frozen vegetables. Blood and urine samples were collected. One hundred-two participants completed the study. Results At baseline, there were no differences in urine pH (6.17 ± 0.42 vs 6.18 ± 0.41), urine titratable acid (21.0 ± 7.3 vs 20.7 ± 9.0 mEq/d), urine ammonia (324 ± 197 vs 348 ± 175 mg/d), serum N-terminal propeptide of type I procollagen (PINP, a bone formation marker, 27.8 ± 8.9 vs 26.3 ± 10.5 ng/ml), serum C-terminal telopeptide of type I collagen (CTX, a bone resorption marker, 0.36 ± 0.18 vs 0.34 ± 0.15 ng/ml), between the control and the intervention groups, respectively. There were no differences in the above parameters between the baseline and at the end of 8-wk for the control group. Compared to the baseline, increased intake of vegetables increased urine pH (6.33, P < 0.05) and serum PINP (29.7 ± 13.6 ng/ml, P < 0.05), and decreased urine titratable acid (17.0 ± 9.4 mEq/d, P < 0.05), urine ammonia (279 ± 151 mg/d, P < 0.05), and serum CTX (0.29 ± 0.11 ng/ml, P < 0.01). Conclusions These data demonstrate that increased vegetable consumption of the types and amounts recommended by the DGA decreases urinary acidity and has positive effects on bone turnover markers. Funding Sources This work was supported by the Agricultural Research Service of the United States Department of Agriculture, #3062–51,000-053–00D.