Providing vegetables at the amount recommended by the Dietary Guidelines for Americans decreases urinary acidity and bone turnover: an 8-wk randomized controlled trial

Authors: Cao, Jay; JAHNS, LISA - Former ARS Employee; Roemmich, James

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2021
Publication Date: 8/12/2021
Citation: Cao, J.J., Jahns, L., Roemmich, J.N. 2021. Providing vegetables at the amount recommended by the Dietary Guidelines for Americans decreases urinary acidity and bone turnover: an 8-wk randomized controlled trial. Journal of Nutrition. 151:3413-3420. https://doi.org/10.1093/jn/nxab255.
DOI: https://doi.org/10.1093/jn/nxab255

Interpretive Summary: Osteoporosis is a chronic disease affecting about 54 million Americans. Fruits and vegetables are healthy foods and may be beneficial to bone health because they contain many essential nutrients and bioactive compounds. We conducted a community-based, 8-week feeding intervention study with overweight and obese adults that reported low vegetable intake. The purpose of study was to investigate whether incorporating extra vegetables into people’s usual diets would be beneficial to bone health. We provided a variety of pre-packaged fresh or frozen vegetables at the amount recommended by the Dietary Guidelines for Americans to 51 subjects and compared bone related measurements to another 51 subjects that received no extra vegetables. We found that eating extra vegetables at or above federal dietary guidance decreased markers of bone loss and may be good for bone health.

Technical Abstract: bjective: Limited evidence from epidemiological and interventional studies suggests fruit or vegetable intake is beneficial to bone health. Our objective was to investigate the extent to which providing vegetables at the Dietary Guidelines for Americans (DGA) recommended types and amounts affects excretion of acid and calcium in urine and bone turnover markers in serum in adults with low FV intake. Methods: One-hundred and ten overweight or obese adults consuming = 1.0 serving of vegetables per day were recruited in a two-arm, parallel-designed, randomized controlled, and community-based 8-week feeding intervention trial. The two arms included (1) an attention control arm and (2) an active intervention arm during which participants received a variety of pre-packaged fresh or frozen vegetables at the DGA recommended amount based on energy needs of each participant and were free to incorporate into their usual diets. Dietary intake was assessed based on the Automated Self-Administered 24-h dietary recall system. Blood and urine samples were collected for bone-related measurements. One hundred and two participants completed the study. Results: At the end of the 8-wk of study, total intake of carotenoids, considered as a biomarker of fruit or vegetable intake, and total blood carotenoid concentrations were greater in the intervention group (2.0 ± 0.2 vs 6.4 ± 0.5 mg/d, P < 0.01, and 2.82 ± 0.15 vs 4.17 ± 0.24 µmol/L, P < 0.01, mean ± SEM, for the control and the intervention groups, respectively), compared to the control group. Dietary potential renal acid load, a measure of dietary acid load, was lower in the intervention group (19.7 ± 1.8 vs 3.4 ± 1.9 mEq/d, P < 0.01). Compared to the control, urine titratable acid decreased (P < 0.01) and urine pH increased (P < 0.05) in the intervention group. Serum C-terminal telopeptide of type I collagen, a bone resorption marker, decreased with the vegetable intervention (P < 0.05). Conclusions: These data demonstrate that providing vegetables at the types and amounts recommended by the DGA to adults with low FV intake decreases urinary acidity and has positive effects on markers of bone metabolism.