Dietary Intake of Vitamin D in Premenopausal, Healthy Vegans was Insufficient to Maintain Concentrations of Serum 25-hydroxyvitamin D and Intact Parathyroid Hormone Within Normal Ranges During the Winter in Finland

Abstract

Objective To study vitamin D status and bone metabolism of premenopausal vegetarians and omnivores during a 1-year period. Design Longitudinal, observational study. Bone mineral density was measured, blood samples from fasting subjects were obtained, and 24-hour urinary samples were collected in February 1994, August 1994, and January 1995. Serum 25-hydroxyvitamin D [S-25(OH)D] and intact parathyroid hormone (Si-PTH) concentrations were measured and intestinal calcium absorption was estimated. Dietary intakes of vitamin D and calcium were calculated. Subjects/setting Six vegans, 6 lactovegetarians, and 16 omnivores living in Helsinki, Finland. Statistical analyses performed Student-Newman-Keuls test; unbalanced, repeated-measures multiple analysis of variance; analysis of covariance; Pearson correlation test; and linear regression analysis. Results Dietary intake of vitamin D was significantly lower in vegans ( P<.05, yearly mean±standard deviation=0.09± 0.06 μg/day) and in lactovegetarians ( P<.05, 0.7±0.4 μg/ day) compared with omnivores (4.0±2.1 (μg/day). Throughout the year S-25(OH)D ( P=.01) concentrations were lower and S-iPTH ( P=.01) concentrations were higher in vegans than in omnivores and lactovegetarians. Bone mineral density in the lumbar region of the spine was lower in vegans (yearly mean±standard deviation=1.034±0.174 g/ cm 2) than in omnivores ( P=.05, 1.177±0.099 g/cm 2) and tended to be lower than that in lactovegetarians ( P=.17, 1.138±0.06 g/cm 2). Bone mineral density in the neck of the femur tended to be lower in vegans (0.843±0.116 g/cm 2) than in omnivores ( P=.07, 0.999±0.138 g/cm 2) and lactovegetarians ( P=.15, 0.961±0.059 g/cm 2). No seasonal variation was found in bone mineral density in the study groups. Conclusions At northern latitudes, dietary intake of vitamin D in vegans was insufficient to maintain S-25(OH)D and S-iPTH concentrations within normal ranges in the winter, which seems to have negative effects on bone mineral density in the long run. Applications An increase in vitamin D intake should generally be recommended for vegans at least during winter, or selections of foodstuffs fortified with vitamin D should be broadened in northern latitudes. J Am Diet Assoc. 2000; 100:434-441.