• Dr. Daniel P. Berthold

Do Vegetarian and Vegan Diets come along with an Increased Risk of Fracture?

Updated: Nov 30, 2020

In German

Very often, we are getting asked whether vegetarian or vegan diets should be preferred over non-vegetarian diets, especially in high-active athletes or during long periods of rehabilitation. Among ethical and religious motivations, the reasons for adoption of these dietary profiles are often related to health-related aspects. (Craig 2009, Dinu, Abbate et al. 2017) In 2017, Dinu et al. reported a significant protective effect of a vegetarian diet versus the incidence and/or mortality from ischemic heart disease and from total cancer. Subsequently, a vegan diet comes along with a significantly reduced risk of incidence from total cancer. (Dinu, Abbate et al. 2017) However, previous epidemiological studies demonstrated that a vegetarian diet is often associated with a lower bone mineral density (BMD) when compared to their counterparts. (Ho-Pham, Nguyen et al. 2009, Tong, Key et al. 2018) Logically, a lower BMD, which can be often found in patients with osteoporosis or reduced long-term weight-bearing, is related to a higher risk of fractures. Interestingly, increased weight-bearing from high body mass index (BMI) is known to strengthen our bones, however, relevant associations between high BMI and increased fracture risks for some other sites such as ankle fractures are described. (Armstrong, Cairns et al. 2012) As such, higher torques from twisting the ankle may result in devasting ankle fractures, (De Laet, Kanis et al. 2005, Armstrong, Cairns et al. 2012) often requiring surgical intervention.

Current literature suggests that lower BMD is often caused by substantially lower intakes of calcium in vegans, lower intakes of dietary protein, and BMI. However, the relationship between these risk factors and increased risk of fractures remain unknown. As such, a novel study from our British colleagues Tammy Tong and al. investigated the risks of total and site-specific fractures in a prospective study design in almost 55,000 participants with an astonishing follow-up for 18 years (in average). (Tong, Appleby et al.) Overall, the authors found that vegans have higher risks of total and some site-specific fractures in the hip, leg, and vertebra when compared to meat-eaters. (Tong, Appleby et al.)This observation is of high clinical relevance as fractures remain a significant burden to patients and to the health system. (Oden, McCloskey et al. 2015) Of interest, the strongest associations were found for hip fractures. This may be related to lower average BMI and lower averages intakes of calcium and protein in the non-meat eater group. This may suggest that food supplementation in non-meat eater is necessary, especially in patients with low calcium, Vitamin D, and protein intake. A daily intake of at least 525mg/day of calcium, however, may be enough to reduce the fracture risk significantly. (Appleby, Roddam et al. 2007) Additionally, current evidence highlights that high protein intake increases intestinal calcium absorption, (Kerstetter, O'Brien et al. 2003) stimulates the production of important growth factors (such as IGF-I; Insulin-like growth factor), (Bonjour 2016) which are associated with better bone health. (Locatelli and Bianchi 2014) As such, non-meat eater may also require additional protein intake. Of interest, older studies from 1979 and 1998 suggested that excessive protein intake would lead to an increased metabolic acid load, which could lead to poorer bone health. (Allen, Oddoye et al. 1979, Barzel and Massey 1998) However, this was not confirmed by novel literature, suggesting that there is no significant association between protein intake and fracture risk. (Darling, Manders et al. 2019)

In a conclusion, as vegans and vegetarians may have an increased risk of fractures, food supplementation of Vitamin D, Calcium, and Protein should be considered. However, excessive intakes should be avoided, as kidney, liver, or parathyroid diseases may result.

References



Allen, L. H., E. Oddoye and S. Margen (1979). "Protein-induced hypercalciuria: a longer term study." The American journal of clinical nutrition 32(4): 741-749.


Appleby, P., A. Roddam, N. Allen and T. Key (2007). "Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford." European journal of clinical nutrition 61(12): 1400-1406.


Armstrong, M. E. G., B. J. Cairns, E. Banks, J. Green, G. K. Reeves and V. Beral (2012). "Different effects of age, adiposity and physical activity on the risk of ankle, wrist and hip fractures in postmenopausal women." Bone 50(6): 1394-1400.


Barzel, U. S. and L. K. Massey (1998). "Excess dietary protein can adversely affect bone." The Journal of nutrition128(6): 1051-1053.


Bonjour, J.-P. (2016). "The dietary protein, IGF-I, skeletal health axis." Hormone molecular biology and clinical investigation 28(1): 39-53.


Craig, W. J. (2009). "Health effects of vegan diets." The American journal of clinical nutrition 89(5): 1627S-1633S.


Darling, A. L., R. J. Manders, S. Sahni, K. Zhu, C. E. Hewitt, R. L. Prince, D. J. Millward and S. A. Lanham-New (2019). "Dietary protein and bone health across the life-course: an updated systematic review and meta-analysis over 40 years." Osteoporosis International 30(4): 741-761.


De Laet, C., J. Kanis, A. Odén, H. Johanson, O. Johnell, P. Delmas, J. Eisman, H. Kroger, S. Fujiwara and P. Garnero (2005). "Body mass index as a predictor of fracture risk: a meta-analysis." Osteoporosis international 16(11): 1330-1338.


Dinu, M., R. Abbate, G. F. Gensini, A. Casini and F. Sofi (2017). "Vegetarian, vegan diets and multiple health outcomes: a systematic review with meta-analysis of observational studies." Critical reviews in food science and nutrition 57(17): 3640-3649.


Ho-Pham, L. T., N. D. Nguyen and T. V. Nguyen (2009). "Effect of vegetarian diets on bone mineral density: a Bayesian meta-analysis." The American journal of clinical nutrition 90(4): 943-950.


Kerstetter, J. E., K. O. O'Brien and K. L. Insogna (2003). "Dietary protein, calcium metabolism, and skeletal homeostasis revisited." The American journal of clinical nutrition 78(3): 584S-592S.


Locatelli, V. and V. E. Bianchi (2014). "Effect of GH/IGF-1 on bone metabolism and osteoporsosis." International journal of endocrinology 2014.


Oden, A., E. V. McCloskey, J. A. Kanis, N. C. Harvey and H. Johansson (2015). "Burden of high fracture probability worldwide: secular increases 2010–2040." Osteoporosis International 26(9): 2243-2248.


Tong, T. Y., T. J. Key, J. G. Sobiecki and K. E. Bradbury (2018). "Anthropometric and physiologic characteristics in white and British Indian vegetarians and nonvegetarians in the UK Biobank." The American journal of clinical nutrition107(6): 909-920.


Tong, Y., P. Appleby, G. Fensom, A. Knuppel, K. Papier, A. Perez-Cornago, R. Wrightson and T. Key "Vegetarian and vegan diets and risks of total and site-specific fractures: results from the prospective EPIC-Oxford study." BMC Medicine.

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