By Reed Mangels, PhD, RD

A recently published study about fracture risk in non-meat eaters has received a lot of media attention. Here’s what you need to know.

What is the study?

The study is from the United Kingdom and was conducted by researchers at Oxford University and the University of Bristol. Study subjects were recruited between 1993 and 2001 and were studied until 2016. About 55,000 men and women were included in the study. At the start of the study, subjects were classified into 1 of 4 dietary groups based on their responses to a questionnaire which asked questions like “Do you eat any meat?” The groups were meat eaters, fish eaters (did not eat meat but ate fish), vegetarians (did not eat meat or fish, but ate one or both of dairy or eggs), and vegans (participants who did not eat meat, fish, dairy, and eggs). At the start of the study there were 29,380 meat eaters, 8,037 fish eaters, 15,499 vegetarians, and 1,982 vegans. 

     Some subjects completed a similar follow-up questionnaire in 2010. The majority of subjects had followed the same diet for years before the start of the study. For example, 88% of fish eaters, vegetarians, and vegans had not eaten meat for at least 5 years before recruitment, 85% of vegetarians and vegans had not eaten fish for at least 5 years before recruitment, and 82% of vegans had not eaten eggs or dairy for at least 3 years before recruitment.

     During the follow-up period, the occurrence of fractures was determined through use of the National Health Service’s records. The study’s goal was to determine if there were differences in fracture risks between vegetarians, vegans, and non-vegetarians.

What did it find?

Over the follow-up period which averaged 17.6 years, there were 3,491 fractures – 566 arm fractures, 889 wrist fractures, 945 hip fractures, 366 leg fractures, 520 ankle fractures, and 467 other fractures. The researchers were not able to determine how many fractures were due to trauma like auto accidents and how many were due to osteoporosis (weak bones).

     Compared with meat eaters, vegetarians and vegans had a higher risk of total fractures and hip fractures and vegans had a higher risk of leg fractures and of vertebral fractures. Vegetarians had a 25% higher risk of hip fractures than did meat eaters while vegans had more than twice the risk. No significant differences were seen between the groups in the risk of wrist or ankle fractures or the risk of arm fractures after controlling for body mass index (BMI).

     Differences in BMI between the groups account for some of the differences in fracture risk. Vegans tend to have a lower BMI on average. A lower BMI has been associated with less dense bones because bones are strengthened by weight-bearing exercise. If a person weighs more, their bones do more weight-bearing. Additionally, some studies have found increased risk of hip fractures with lower BMIs, possibly because of less fat to cushion the hip when a fall occurs.

     The vegans had lower average intakes of calcium and protein from food. The average calcium intake of vegans was 591 milligrams per day, considerably below the approximately 1,000 milligrams per day which was the average for the other diet groups. However, even when only those study participants who had calcium intakes above the U.K. recommendations were examined, the vegans still had a higher risk of bone fractures. The differences in dietary protein and calcium intake do not account for all the differences in fracture risk between the groups and the researchers were unable to explain why differences in fracture risk persisted even after their data were adjusted for differences in BMI and calcium and protein intake.

     Additionally, there was a higher risk of total fractures among vegans who were not very physically active and who had a low BMI but vegetarians (not vegans) with a higher BMI had a higher risk of hip fracture. There were a limited number of subjects who were in these subgroups which makes it difficult to be confident that these results would hold in a larger group.

What are the study’s limitations?

While the investigators examined dietary calcium intake, they did not determine if there were differences in intake of calcium supplements, nor did they investigate vitamin D intake or status. Adequate vitamin D is needed to promote calcium absorption. They also did not investigate vitamin B12 status or intake. Inadequate vitamin B12 is associated with an increased fracture risk.

     Because of the observational nature of this study, it is not possible to say if changes in vegans’ dietary or supplement practices (such as increased calcium, vitamin D, vitamin B12, or protein intake) could have affected their risk of fracture.

Are there practical implications?

This study alerts vegans that they may be at increased risk for several types of fractures including hip and vertebral fractures. Vegans should follow general recommendations to promote healthy bones including:

• Meeting calcium recommendations,
• Getting adequate vitamin D,
• Getting enough protein,
• Using fortified foods and/or supplements to meet recommendations for vitamin B12,
• Getting weight-bearing exercise.

Tong TYN, Appleby PN, Armstrong MEG, et al. Vegetarian and vegan diets and risks of total and site-specific fractures: results from the prospective EPIC-Oxford study. BMC Med. 2020;18(1):353.