Does a vegetarian diet weaken your bones?

Vegans have, on average, the lowest bone density of all dietary groups, and vegetarians also score lower than meat-eaters. This is a consistent pattern across multiple review studies. At the same time, these are averages: individual lifestyle, supplementation and body weight make a large difference.

The picture is similar for fractures. Large prospective studies show that vegans face a clearly higher fracture risk than meat-eaters, with vegetarians falling in between. A meta-analysis of 20 studies (comprising over 243,000 participants) found that a plant-based diet is associated with more than twice the risk of osteoporosis in the lumbar spine. It should be noted that this analysis showed considerable variation between studies, making the precise magnitude of that risk uncertain. Hip fracture risk was elevated but statistically uncertain. People who have eaten a plant-based diet for 10 years or longer face a somewhat greater risk of hip fractures than those who have done so for a shorter period.

The main explanation is a shortage of calcium, vitamin D and protein. Vegans have the lowest calcium intake of all groups, and without fortified products or supplementation they face a real risk of deficiencies that undermine bone health. Vitamin B12 and iodine are additional points of concern. Supplementation with vitamin D and calcium, combined with adequate protein, appears to reduce the risk, but the evidence for this is still limited.

There is also an older study suggesting that long-term lacto-ovo-vegetarians have less bone loss at age 80 than meat-eaters (18% versus 35%). This finding is in tension with more recent results, and the study has methodological limitations. The source of protein may play a role: dairy contains calcium, whereas a fully plant-based diet does not provide this unless one actively takes supplements or consumes fortified products.

All available data are observational. This means we cannot be certain whether the diet itself is the cause, or whether it is partly linked to other factors such as body weight or physical activity. For vegans it is sensible to monitor calcium and vitamin D intake carefully, and to consciously include adequate protein in the diet.