New results from the EPIC-Oxford study suggest that vegans, vegetarians and pescatarians (people who eat fish but no other meat) may be at higher risk of bone fractures, compared with meat eaters. In particular, the results showed that vegans had a higher risk of fractures anywhere in the body (total fractures), as well as fractures of the legs and vertebrae, compared with meat eaters. In addition, vegans, vegetarians and pescatarians had a significantly greater risk of hip fractures. In all cases, however, the increased fracture risk was reduced if participants had a higher body mass index (BMI) and higher calcium and protein intake. There were no differences in the risks of wrist or ankle fractures by diet group with or without BMI adjustment, nor for arm fractures after BMI adjustment.
Dr Tammy Tong, Nutritional Epidemiologist at NDPH’s Cancer Epidemiology Unit and the lead author said: ‘This is the first comprehensive study on the risks of both total and site-specific fractures in people of different diet groups. We found that vegans had a higher risk of total fractures which resulted in close to 20 more cases per 1000 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 1000 people over 10 years.’
The results are based on data from nearly 55,000 participants in the EPIC-Oxford study: a cohort of men and women living in the UK recruited between 1993 and 2001, which includes many vegetarians, vegans and pescatarians. Researchers from NDPH and the University of Bristol followed the cohort over an average 18-year period up to 2016, during which time almost 4,000 fractures occurred in total.
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. Calcium is an essential component of bone and vital for preventing brittle bone disease (osteoporosis). Protein may also be important for bone health because it increases intestinal calcium absorption and stimulates the production of insulin-like growth factor, which could promote bone growth and development.
Several mechanisms have been proposed to explain the apparent link between low BMI and increased hip fracture risk. These include high BMI scores being associated with greater cushioning against impact force during a fall; enhanced production of oestrogen (which maintains bone density); or stronger bones from increased weight-bearing.
‘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. ‘But it is worth bearing in mind that well-balanced and predominantly plant-based diets can result in improved nutrient levels and have been linked to lower risks of diseases including heart disease and diabetes. Individuals should take into account the benefits and risks of their diet, and ensure that they have adequate levels of calcium and protein and also maintain a healthy BMI.’
This investigation did not consider the cause of fracture, or calcium that was taken in supplement form. The majority of the study participants were white Europeans, hence the applicability to other populations may be limited.
The study is published today in BMC Medicine.