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

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

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

A western Canadian metropolitan area.

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.

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.

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.

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.