Vegan diet and bone fractures
Two studies have now reported an increased risk of fractures in people following a vegan diet. The first was a study published in November 2020 and was a new analysis from the EPIC-Oxford study, one of the longest running and largest studies investigating the health of vegetarians and vegans. There is a lot to digest in the paper with some quite complicated analysis. Of note, the first report from the EPIC-Oxford study on bone health published in 2007 showed no differences in the self-reported incidence of fractures between meat eaters, fish eaters and lacto-ovo vegetarians, but vegans had a 30% higher risk of fracture compared with meat eaters . However, when the results were adjusted for calcium intake, those consuming at least 525mg of calcium per day, regardless of diet pattern, showed no increase in risk of fracture demonstrating that if the diet contains an adequate amount of calcium there is no disadvantage for bone health on a plant-based diet.
The updated study results show an increased rate of fracture in those not consuming meat. This was not exclusive to vegans and included vegetarians and fish eaters, but the effect was more pronounced in the vegan group. For vegans the impact was greatest for hip fractures with a 231% elevated risk compared to meat eaters. Vegans had a 43% increased risk of developing any fracture compared to meat eaters. In absolute terms, this amounted to 19 more cases of fractures in vegans for every 1000 people over 10 years.
There is no question of poor study design or industry influence with this study, which has a robust design with rigorous analysis of the data. Two of the authors are vegan. The points of interest are that body mass index (BMI) had a major influence on fracture risk with a BMI less than 22.5 associated with the increased risk. For vegans with a BMI greater or equal to 22.5, this risk disappeared. The fracture risk was also only increased in women (who made up more than two-thirds of the participants) and not men. Vegans in this study had a lower than recommended intake of calcium and a lower use of hormone replacement therapy in women compared with meat-eaters, factors that are relevant to the risk of bone fractures. The mean calcium intake for vegans was around 600mg/day, so not meeting UK recommendations for 700mg/day. Non-meat eaters also had a lower protein intake than meat-eaters, which appeared to be contribuing to the risk of fractures in the analysis. We also know from prior reports from the EPIC-Oxford cohort that the vegans had lower B12 and vitamin D intakes compared to the non-vegans. Only around 50% of vegan participants in this study were taking dietary supplements, which means that 50% were relying on food sources of vitamin B12 and vitamin D, which we know are inadequate. These participants were recruited in the 1990’s at a time when fortification of plant-based alternatives was not common and knowledge and information on healthy vegan diets was less accessible.
The major limitation is that the study cannot tell us the cause of the fractures i.e. are they due to poor bone health or due to accidents. There was also no determination of bone mineral density. The study did not correlate fracture rates with vitamin D status, a major factor in bone health. So, overall the study does not prove a causal relationship between diet and fractures but an association. Having said that, we need to pay attention to these results rather than discount them.
The second study is a report from the Adventist Health Study 2, which includes more than 96,000 Adventists from North America that have been followed since 2002. The study showed that vegans have a 55% increased risk of developing a hip fracture compared to omnivores. Again, this figure sounds alarming, but in absolute terms amounts to 1.5 extra hip fractures per 1000 vegans per year. Again, the increased risk was only seen in women, not men, and this time the risk completely disappeared in vegans taking both calcium and vitamin D supplements.
For me the take home messages are the importance of adopting a healthy vegan diet, paying attention to nutrients such as calcium, zinc, B12, vitamin D. A healthy vegan diet is one that is composed of a variety of fruits, vegetables, whole grains, beans, nuts and seeds and minimises processed/packaged foods. It’s also helpful to incorporate fortified foods and drinks such as soya milk, yogurt and calcium-set tofu. Weight bearing physical activity and muscle strengthening are vitally important for bone health and may need to be emphasised more for those on a 100% plant-based diet, along with other healthy lifestyle practice that impact bone health; avoiding alcohol and tobacco smoking, limiting caffeine, fizzy drinks and added salt. It may also be beneficial to aim for the middle of the BMI range rather than a BMI of <20.
We must not forget that both the EPIC-Oxford and Adventist Health Studies have shown us that a vegan diet is associated with around a 50% reduction in risk of high blood pressure, significantly lower levels of blood cholesterol, a 25–30% reduction in ischaemic heart disease (this includes vegetarians as well), 19% reduction in cancer risk and a 30–40% reduction in risk of type 2 diabetes in those not eating meat. These are all major causes of death and disability in the UK and a far greater risk to personal and public health than bone fractures.
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