Vegetarians, pescatarians, and vegans may be at higher risk of bone fractures, according to a large long-term study published in BMC Medicine.
The study, which incorporated around 55,000 people of varying diets, discovered that fish-based and vegetarian diets shared a small but significant increase in risk of bone fracture, while veganism put participants at a 43 percent higher risk of fractures.
"This is the first comprehensive study on the risks of both total and site-specific fractures in people of different diet groups,” said lead author Dr Tammy Tong, nutritional epidemiologist at the Nuffield Department of Population Health, University of Oxford, in a statement.
Beginning recruitment in 1993, the study followed 29,380 meat-eaters, 8,000 pescatarians (eating fish but not meat), 15,500 vegetarians, and 2,000 vegans over an average of 18 years and looked for occurrence of bone fractures. Over the study period, a total of 3,931 fractures were reported. Those on diets without meat saw higher incidences of fractures of the hip, as well as legs, arms, ankles, ribs, and other major sites.
The study follows previous evidence that lower protein and calcium intake correlates with poorer bone health, alongside low BMI. While the authors state there is not enough evidence to draw conclusions as to why these diets may increase fracture risk, when the study accounted for differences in these factors, the risk of bone fracture was partially reduced.
Despite this, accounting for these factors still leaves non-meat-eaters at 1.3 times the risk of fracture.
"Previous studies have shown that low BMI is associated with a higher risk of hip fractures, and low intakes of calcium and protein have both been linked to poorer bone health. This study showed that vegans, who on average had lower BMI as well as lower intakes of calcium and protein than meat-eaters, had higher risks of fractures at several sites,” said Dr Tong.
The study at this time is purely correlation and more in-depth research will be needed to discern a reason as to why the risk is elevated in vegans. The sample size was much smaller in the vegan group, which should be considered when drawing conclusions, alongside the fact that supplementation of extra calcium and other nutrients were also not accounted for. Some have also suggested the difference could be in the way calcium is absorbed – various factors can account for calcium uptake, including Vitamin D levels, and these may differ between diets.
The authors note that further study will be needed to incorporate different ethnicities to the predominantly white Europeans used in the sample groups as generalizing results across other populations or ethnicities is limited.
Vegan and vegetarian diets have become increasingly popular over the past decade. According to The Vegan Society, veganism has quadrupled in the UK between 2014-2019, and up to 6 percent of Americans report being vegan, a 500 percent increase from 2014, with people turning to plant-based alternatives for health, environmental, and ethical reasons.
However, as the diet trends upwards, the need for research into its application also increases. Maintaining sufficient levels of protein and calcium in these diets requires dietary monitoring, and research such as this will become essential in finding ways to apply these diets with the least risk to the body as possible.