Vegetarian women at greater risk of hip fracture than meat-eaters

Vegetarian women are more likely to experience hip fracture compared to regular meat-eaters, results from the UK Women’s Cohort Study have shown.

“Overall, vegetarians but not occasional meat-eaters or pescatarians were at a higher risk of hip fracture compared to regular meat-eaters in this cohort of UK women,” said the researchers, led by James Webster of the Nutritional Epidemiology Group, University of Leeds, Leeds, UK.

“Further research is needed to confirm this in other populations, such as men and non-European populations, and to identify the factors responsible for the observed risk difference,” they added.

Webster and his team recruited a total of 26,318 women, ages 35‒69 years, and classified them as regular meat-eaters (≥5 servings/week), occasional meat-eaters (<5 servings/week), pescatarian (ate fish but not meat), or vegetarian (ate neither meat nor fish) based on a validated 217-item food frequency questionnaire completed in 1995‒1998.

The researchers identified incident hip fractures via linkage to Hospital Episode Statistics up to March 2019. They estimated the associations between each diet group and hip fracture risk using Cox regression models over a median follow-up of 22.3 years.

Overall, 822 hip fracture cases were observed among participants (556,331 person-years). After adjusting for confounders, vegetarians (hazard ratio, 1.33, 95 percent confidence interval [CI], 1.03‒1.71) exhibited a higher risk of hip fracture than regular meat-eaters. [BMC Med 2022;20:275]

The increased risk, however, was not observed among occasional meat-eaters (HR, 1.00, 95 percent CI, 0.85‒1.18) and pescatarians (HR, 0.97, 95 percent CI, 0.75‒1.26). Furthermore, body mass index (BMI) appeared to have no significant impact in any diet group (p_interaction=0.3).

“Our findings largely concur with the results of the only other two cohort studies on this topic, strengthening the evidence of a higher risk of hip fracture in UK vegetarian women,” the researchers said. [BMC Med 2020;18:353; Am J Clin Nutr 2021;114:488-495]

Body anthropometrics

Other studies showed that adherence to diets low in mean intake, such as the Mediterranean diet and Alternative Healthy Eating Index, was protectively associated with hip fracture risk, while adherence to Western diets, in which meat consumption is high, positively correlated with hip fracture. [Eur J Nutr 2018;57:2147-2160; J Hum Nutr Diet 2019;32:98-107; Adv Nutr (Bethesda) 2019;10:219-236]

In contrast, the Adventist Health Study-2 found an inverse association between total meat intake and hip fracture. [Public Health Nutr 2014;17:2333-2343]

“These results cannot be fairly compared with risks in vegetarians and nonvegetarians, which no other study has directly assessed,” Webster and colleagues said.

In the current study, differences in body anthropometrics between diet groups could partially explain the increased hip fracture risk among vegetarians relative to meat-eaters. Another possible explanation was the lower intake of nutrients important to bone health that are abundant in animal products, according to the researchers.

Earlier studies reported lower dietary intakes of protein, calcium, vitamin D, and vitamin B12 in vegetarians and suggested protective benefits of these nutrients with hip fracture risk. [Public Health Nutr 2003;6:259-269; Am J Clin Nutr 2014;100(Suppl 1):329s-335s; Sci Rep 2015;5:8; Curr 2015;13:256-261]

“Since the higher risk of hip fracture in vegetarians remained after adjustment for BMI and several dietary nutrient intakes, other factors may be important,” the researchers said.

“[F]urther research exploring the roles of BMI and nutrients abundant in animal-sourced foods is recommended so that public health interventions and policy guidelines aiming to reduce hip fracture risk in vegetarians through dietary change or weight management can be formed,” they noted.