Spinal bone mineral density in premenopausal vegetarian and nonvegetarian women: cross-sectional and prospective comparisons.

OBJECTIVE: To compare spinal bone mineral density (BMD) and 1-year BMD change between premenopausal vegetarian and nonvegetarian women.

DESIGN: Cross-sectional comparison of spinal BMD at baseline and prospective comparison of a subsample.

SETTING: A western Canadian metropolitan area.

SUBJECTS/SAMPLES: Healthy vegetarian (n = 15 lacto-ovo-vegetarian, n = 8 vegan) and nonvegetarian (n = 22) women aged 20 to 40 years, with regular menstrual cycles and stable body weight completed baseline measurements. Twenty of these women (6 lacto-ovo-vegetarian, 5 vegan, 9 nonvegetarian) participated in repeat measurements at approximately 13 months.

STATISTICAL ANALYSES PERFORMED: Descriptive statistics, independent sample and paired t tests, 1-way analysis of variance, correlation analysis, and stepwise multiple regression were used to compare groups and to assess associations with BMD.

RESULTS: At baseline, subjects were 27.2 +/- 5.1 years old. Vegetarians had lower body mass index (21.1 +/- 2.3 vs 22.7 +/- 1.9, P < .05) and percent body fat (24.0 +/- 5.5% vs 27.4 +/- 5.1%, P < .05); they also tended to have lower BMD (1.148 +/- 0.111 g/cm2 vs 1.216 +/- 0.132 g/cm2, P = .06), although this was not apparent with weight as a covariate (P = .14). Baseline BMD was predicted by vitamin B-12 intake and total body fat (R2 = .24, P = .001). Participants in the follow-up differed only in their being older than nonparticipants. Over 1 year, mean BMD increased significantly (1.1%): by diet group, nonvegetarians' BMD increased but vegetarians' BMD was unchanged. No other monitored variables were associated with BMD change.

APPLICATIONS/CONCLUSIONS: Vegetarian women should be aware of links between low BMD and low body weight/body fat, and should maintain adequate intakes of nutrients believed to affect BMD.