Vegans may have higher risk for bone fractures
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Vegans have a higher risk for total fractures when compared with meat eaters, and vegans, fish eaters and vegetarians have an elevated risk for hip fractures, according to findings published in BMC Medicine.
“This is the first comprehensive study on the risks of both total and site-specific fractures in people of different diet groups,” Tammy Y.N. Tong, PhD, a nutritional epidemiologist in the Nuffield Department of Public Health at the University of Oxford, U.K., said in a press release. “We found that vegans had a higher risk of total fractures, which resulted in close to 20 more cases per 1,000 people over a 10-year period compared to people who ate meat. The biggest differences were for hip fractures, where the risk in vegans was 2.3 times higher than in people who ate meat, equivalent to 15 more cases per 1,000 people over 10 years.”
Tong and colleagues conducted a prospective cohort study of 54,898 participants who were recruited from across the United Kingdom from 1993 to 2001. At recruitment, participants completed a questionnaire in which they provided information about diet, sociodemographic characteristics, lifestyle and medical history. Similar questions were asked in a follow-up questionnaire sent to participants in 2010. Based on their answers, participants were categorized as meat eaters, fish eaters (did not eat meat, but ate fish), vegetarians (did not eat meat or fish, but ate dairy or eggs) or vegans (did not eat meat, fish, dairy or eggs).
Researchers linked each participant to National Health Service records through March 2016 in England; May 2016 in Wales; and October 2016 in Scotland. Data on first recorded hospital admission or death from total and site-specific fractures were collected. Site-specific fractures analyzed included arm, wrist, hip, leg, ankle and other. The other category included the clavicle, rib and vertebra.
The study population included 29,380 meat eaters, 8,037 fish eaters, 15,499 vegetarians and 1,982 vegans. During a mean 17.6 years of follow-up, there were 3,941 cases of total fractures, 566 arm fractures, 889 wrist fractures, 945 hip fractures, 366 leg fractures, 520 ankle fractures and 467 fractures in the other category.
After adjusting for confounders and BMI, vegans (adjusted HR = 1.43; 95% CI, 1.2-1.7) had a higher risk for total fractures compared with meat eaters. Vegans also had the highest elevated risk for hip fractures (aHR = 2.31; 95% CI, 1.66-3.22) when compared with meat eaters. An increased risk for hip fractures was also found for fish eaters (aHR = 1.26; 95% CI, 1.02-1.54) and vegetarians (aHR = 1.25; 95% CI, 1.04-1.5). Findings for both total fractures and hip fractures were stronger before adjusting for BMI, but remained significantly stronger for vegans after adjustments for calcium and protein.
Vegans also had a higher risk for leg fractures compared with meat eaters (aHR = 2.05; 95% CI, 1.23-3.41). For other sites, vegans had an elevated risk for vertebral fractures (aHR = 2.42; 95% CI, 2.31-4.48), but not for clavicle or rib fractures. There were no differences in risk for any of the groups for arm, wrist or ankle fractures after adjusting for BMI.
Researchers attributed the higher risks in the nonmeat-eating groups to a lower BMI and possibly lower intakes of calcium and protein.
“More studies are needed, especially from non-European and contemporary populations, to examine the generalizability of our findings and to explore possible heterogeneity by factors including age, sex, menopausal status and BMI,” the researchers wrote. “Future work might benefit from examining possible biological pathways by investigating serum levels of vitamin D, vitamin B12, or insulin-like growth factor I, or in assessing the possible roles of other nutrients that are abundant in animal-sourced foods.”
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Tong and colleagues are experts in the area of vegetarian nutrition, and the study highlights important considerations for diet and health related to fracture risk. Although several important covariates were included in the models, some key potential confounders were not accounted for. Adjustments for vitamins D and B12 and fat intake, which are known to influence bone health, were not included.
Menstrual cycle history, reproductive disorders and disordered eating patterns have been shown to be strong predictors of bone injury in both females and males. It would be informative to readers if the questions on menstrual cycle history in the EPIC questionnaire were explored and included as adjustments. The EPIC-Norfolk Physical Activity Questionnaire was “aimed at assessing total energy expenditure” fitness and unable to identify types of bone-loading exercise protocols, such as strength or resistance training and high-impact exercise. More discussion on this important factor is warranted in the paper, including the need for updated physical activity questionnaires.
Continued collection and updating of dietary data in this cohort should reflect an expanding marketplace for vegan-appropriate foods. Accounting for plant-sourced alternatives is key, as their exclusion may preclude the applicability of these study findings to current vegans. The determinants of fracture risk are not exclusive to vegans and may occur with any dietary pattern. The vegan diet and “fitness” lifestyles described in the study do not reflect those of most current vegans, which include many novel fortified plant-sourced food products and meat alternatives, and the implications of their findings should indicate this.
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