Do We Need to Be Concerned about Bone Mineral Density in Vegetarians and Vegans?

Spine, hip, and femoral neck bone mineral density in relation to vegetarian type and status among Taiwanese adults

We determined the association of vegetarian type and status with bone mineral density (BMD) Z-scores at the spine, hip, and femoral neck. Compared to non-vegetarians, current vegetarians, especially vegans, lacto-vegetarians, and lacto-ovo-vegetarians had lower Z-scores at multiple sites. Sole reliance on a vegetarian diet might be detrimental to the bone.

PURPOSE

The impact of vegetarian diets on BMD is contentious. We determined the association of vegetarian type and status with the spine, hip, and femoral neck BMD Z-scores.

METHODS

We analyzed data from 20,110 Taiwan Biobank volunteers. BMD was measured using dual-energy X-ray absorptiometry (DXA). The vegetarian status (non-, former, and current vegetarians) and type (non-vegetarians, ovo-vegetarians, lacto-vegetarians, lacto-ovo-vegetarians, and vegans) were determined using questionnaires.

RESULTS

The participants consisted of 12,910 women and 7200 men, with a mean age of 55.5 years. Based on vegetarian status (reference: non-vegetarians), current vegetarians had significantly lower BMD Z-scores at the spine (unstandardized regression coefficient, B =  - 0.195, p = 0.006), left hip (B =  - 0.125, p = 0.008), and right hip (B =  - 0.100, p = 0.027), respectively. Based on vegetarian status and type (reference: non-vegetarians), current vegans and non-vegans had notably lower BMD Z-scores at specific skeletal sites. For non-vegans, the BMD Z-scores were significant at the spine (B = -0.184, p = 0.010), left hip (B =  - 0.124, p = 0.010), and left femoral neck (B =  - 0.125, p = 0.012). For current vegans, however, the BMD Z-scores were significant only at the right hip (B =  - 0.232; p = 0.028). Nonetheless, after stratifying vegetarian diet into more subgroups, current vegans exhibited a significant reduction in BMD Z-scores at the spine and right hip, with B-coefficients of - 0.326 and - 0.238, respectively. Current lacto-vegetarians also had significantly lower Z-scores (p < 0.05) at the spine (B =  - 0.459), left hip (B =  - 0.313), and right hip (B =  - 0.214). Moreover, current lacto-ovo-vegetarians had significantly lower Z-scores at the spine (B =  - 0.175) and left hip (B =  - 0.115).

CONCLUSION

Current vegetarians, particularly vegans, lacto-vegetarians, and lacto-ovo-vegetarians, demonstrated significantly lower BMD Z-scores at various skeletal sites compared to non-vegetarians. Sole reliance on a vegetarian diet might be detrimental to the bone.

Fracture Risk in Vegetarians and Vegans: the Role of Diet and Metabolic Factors

PURPOSE OF REVIEW

There is strong evidence that poor dietary intake of certain micro- and macro-nutrients can negatively affect bone health. It is unclear if diet is the primary culprit for poor bone health in the vegan population.

RECENT FINDINGS

Plant-based diets are gaining public interest since they may improve metabolic health. Studies that examine vegetarians and vegans together show a lower bone mineral density (BMD), but not always increased fracture risk compared to omnivores. However, vegans consistently have higher risk of fracture at multiple bone sites, especially at the hip. There is higher fracture risk in vegans which may be due to calcium and vitamin D intake, as well as amount of dietary protein and quality. Other nutrients (B vitamins, Se, Zn, Fe, iodine) or physiological factors (lower body mass index, microbiome, or endocrine profile) may also play a role but have not been examined and require further study.

The impact of plant-based diets on female bone mineral density: Evidence based on seventeen studies

BACKGROUND

An increase in awareness of plant-based diets has brought forth numerous studies on bone mineral density (BMD). The present systematic review and meta-analysis was designed to compare the effect between plant-based diets and omnivores on female BMD.

METHODS

We searched the Cochrane Library, PubMed, EMBASE, and Web of Science and up to July 1, 2020. Mean difference (MD) with its 95% confidence interval (CI) was estimated to compare the outcomes of the groups. We compared BMD at the lumbar spine, femoral neck and whole body respectively between plant-based diets and omnivores. In addition, we performed subgroup analyses according to different clinical characteristics for further exploration. Two reviewers assessed trial quality and extracted data independently. All statistical analyses were performed using standard statistical procedures provided in Review Manager 5.2.

RESULTS

A total of 17 cross-sectional studies including 13,888 patients were identified for the present meta-analysis. Our pooled result indicated that population with plant-based diets had lower BMD than omnivores at the lumbar spine (MD -0.03; 95% CI -0.04 to -0.02; P < .0001), femoral neck (MD -0.04; 95% CI -0.05 to -0.03; P < .00001) and whole body (MD -0.04; 95% CI -0.06 to -0.01; P = .01), respectively. Further exploration indicated that especially females with plant-based diets experienced significantly lower BMD at lumbar spine (MD -0.03; 95% CI -0.04 to -0.02; 3173 pts), femoral neck (MD -0.04; 95% CI -0.05 to -0.03; 10,656 pts) and whole body (MD -0.05; 95% CI -0.10 to -0.00; P = .04). In addition, we performed subgroup analyses and found lower BMD at lumbar spine and femoral neck in both vegetarians and vegans.

CONCLUSIONS

The present meta-analysis indicated that plant-based diets may be correlated with lower BMD of women when compared with omnivore population. However, this does not diminish the fact that a plant-based diet can be a harmful option to the overall bone health of population and more prospective researches are needed to clear the impact of plant-based diets on bone health.

Comparison of human bone mineral densities in subjects on plant-based and omnivorous diets: a systematic review and meta-analysis

BACKGROUND

The increased consumption of plant-based diets has encouraged studies of bone mineral density (BMD). The present systematic review and meta-analysis compared the effects of plant-based and omnivorous diets on BMD.

METHODS

We searched the Cochrane Library, PubMed, EMBASE, and the Web of Science to July 1, 2020. We used the mean differences (MDs) with 95% CIs to compare group outcomes. We compared the lumbar spine, femoral neck, and whole-body BMDs of those on plant-based and omnivorous diets. We performed subgroup analyses by various clinical characteristics. Two reviewers independently assessed trial quality and extracted data. All statistical analyses were performed using Review Manager version 5.2.

RESULTS

A total of 17 cross-sectional studies including 13,888 patients were identified. The pooled results indicated that those on plant-based diets (compared to omnivores) exhibited lower BMDs at the lumbar spine (MD - 0.04; 95% CI - 0.06 to - 0.02; P < 0.0001) and femoral neck (MD - 0.04; 95% CI - 0.05 to - 0.02; P < 0.00001), and a reduced whole-body BMD (MD - 0.03; 95% CI - 0.06 to - 0.01; P = 0.0009). Both vegetarians and vegans exhibited lower lumbar spine, femoral neck, and whole-body BMDs than omnivores.

CONCLUSIONS

Plant-based diets were associated with lower BMDs than those of an omnivore population. Plant-based diets may compromise overall bone health; prospective research is required.

Risks and benefits of vegan and vegetarian diets in children

In parallel with increased public awareness of the health and environmental benefits of consuming a plant-based diet, the numbers of people who identify as vegan has increased sharply. The question of whether vegetarian and vegan diets are appropriate for children is a longstanding and unresolved controversy. The more restrictive the diet and the younger the child, the greater the risk of nutritional deficiency. Nutrients of potential concern are protein quantity and quality, iron, zinc, selenium, calcium, riboflavin, vitamins A, D, B12 and essential fatty acids. Although intakes and status of some nutrients (e.g. vitamin D and iron) are low in many children, vegan children are particularly susceptible due to inadequate supply and/or excess dietary fibre as well as other components that limit bioavailability. Although position papers from North America state that well-planned vegetarian and vegan diets, supplemented appropriately, are suitable for all life stages, European statements include strong recommendations to parents that vegan diets should not be adopted by children without medical and dietetic supervision. Case histories of malnutrition and serious harm persist, including irreversible neurological damage due to vitamin B12 deficiency among un-supplemented children. The evidence available to evaluate the nutritional appropriateness of vegetarian diets for children is inadequate and dated. Although nutritionally adequate vegetarian diets are more easily achieved, successful provision of a complete vegan diet for a young child requires substantial commitment, expert guidance, planning, resources and supplementation.