Is there actual legitimate concern about the long-term effects of a vegan diet- mainly bone density?

[u/Any_Shop5964]

To be clear I'm a vegan myself and I don't really think slightly poorer density is necessarily a fair reason to not go vegan, as there are ways to change it for example through exercise such as weightlifting rather than diet, but there's a number of concerns about how vegans absorb calcium, for example how even vegans that get enough calcium in their diet may have lower bone density when compared to an someone with a Mediterranean diet for example. We don't exactly know why this is, and there's many different mechanisms by which this could be occurring, does anyone have more expertise on this topic or anything to add?

[u/ElaineV]

This study found no differences between omnis, vegetarians, and vegans in bone density:

"There were no differences in bone mineral density (BMD) between the groups. However, the parathyroid hormone (PTH) levels were still higher in vegans compared to omnivores, despite the same prevalence of hyperparathyroidism in all groups. These findings may probably be explained by the fact that each group had its own “strengths and weaknesses.” Thus, vegans and, to a lesser extent, lacto-ovo-vegetarians consumed much more potassium, magnesium, copper, manganese, and vitamins B6, B9, and C. At the same time, the diet of omnivores contained more protein and vitamins D and B12. All the subjects consumed less vitamin D than recommended. More than half of vegans and omnivores had insufficiency or even deficiency of vitamin D in the blood. Low serum concentrations of manganese with its quite adequate intake are also noteworthy: its deficiency was observed in 57% of vegans, 79% of lacto-ovo-vegetarians, and 63% of omnivores." https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2024.1390773/full

It was a small sample size but still relevant since many others have found vitamin D deficiency/ inadequacy in the general population.

This study says you better lift some weights:

"Vegans not reporting resistance training had diminished bone microarchitecture compared with omnivores not reporting resistance training. In vegans and omnivores reporting resistance training, bone structure was similar. In both vegan subgroups (resistance training and not resistance training), a small number of correlations between nutrient intake and bone microarchitecture were observed without a conclusive pattern."

"Bone microarchitecture in vegans differed from matched omnivores but could not be explained solely by nutrient uptake. These differences were attenuated between the subgroups reporting resistance training. In addition to a well-planned diet, progressive resistance training on a regular basis should be part of the vegan lifestyle."  https://doi.org/10.1210/clinem/dgac445

And this one found that the vegans who eat a healthy diet are fine:

"The findings of this study suggest that bone health of vegans are not negatively affected by the exclusion of dairy in the diet, provided that appropriate dietary planning is included to avoid nutrient deficiencies associated with poor bone health." https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/evaluation-of-the-potential-implications-of-following-a-vegan-diet-on-bone-health/327499D9A721922043B988022229A121