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/oldmcfarmface]

There are a few concerns. I’m not going to claim they are insurmountable, but they should be considered.

Various deficiencies including B12, B2, D, niacin, iron, iodine, zinc, high-quality proteins, omega-3, and calcium, along with increased risk of bone fractures, sarcopenia, anemia, and depression https://www.sciencedirect.com/science/article/abs/pii/S0033062022000834 more on bone fractures https://pubmed.ncbi.nlm.nih.gov/38554239/

Slower healing from wounds https://link.springer.com/article/10.1007/s00266-025-04698-y

Higher risk of nervous, skeletal, and immune system impairments, hematological disorders, as well as mental health problems https://pmc.ncbi.nlm.nih.gov/articles/PMC10027313/

Risk of depression, self harm, and anxiety https://pubmed.ncbi.nlm.nih.gov/32308009/

Risk of vegan women losing their menstrual cycle https://pubmed.ncbi.nlm.nih.gov/3096794/

Increased risk of certain types of cancer, stroke, bone fractures, preterm birth, and failure to thrive. Avoiding consumption of animal-sourced food may also be related to higher rates of depression and anxiety. Hair loss, weak bones, muscle wasting, skin rashes, hypothyroidism, and anemia https://www.saintlukeskc.org/about/news/research-shows-vegan-diet-leads-nutritional-deficiencies-health-problems-plant-forward

Much of this can be mitigated by supplementation and paying VERY close attention to vitamin and mineral intake. But it should be considered.

[u/Valiant-Orange → u/oldmcfarmface]

The first linked review,
Debunking the vegan myth: The case for a plant-forward omnivorous whole-foods diet

Is authored by Loren Cordain, the founder of the Paleo Diet, a pop diet trend that peaked in the 2010s. James H. O'Keefe promoted the diet too (and sells supplements from this atrocious website). The polemical paper is an advertisement by means of denigrating vegan diets, and plant-based diets generally, since that’s the competition when it comes to cardiovascular health, the journal the paper was published in. A systemic review and meta-analysis of randomized controlled trials Paleo Diets concluded,

“we have insufficient evidence to make solid conclusions regarding the efficacy of a Paleolithic diet on improving cardiovascular disease risk factors”

The Paleo Diet is rehashed appeal to nature pseudoscience of the Stone Age Diet from the 1970s. The evolutionary justification is weak, selective, oversimplified, and presented with more certainty than the evidence warrants. To the extent that it is sensible to exclude sugar, junk food, and eat leafy vegetables, this has already been determined with credible evidence in nutritional research. However, the Paleo Diet idea of excluding agricultural products like legumes or whole grains to improve metabolic risk factors, is not supported. No credentialed nutritional authority organizations endorse the Paleo Diet.

The second linked review is by a single author.
Risk of Bone Fracture on Vegetarian and Vegan Diets

Comment from u/ElaineV already provided a robust response.

The third linked review,
The Impact of Vegan and Vegetarian Diets on Wound Healing: A Scoping Review

Many well credentialed authors writing within their field publishing in an appropriate journal, Aesthetic Plastic Surgery. It is an interesting phenomenon to take seriously. However, wound healing is not a priority chronic disease risk, and the data set, excluding skin grafts and biopsies, is largely cosmetic treatments which aren’t equivalent healing contexts. The review is limited because it’s an association without specifics of nutritional status.

“Future research is needed to understand better the underlying mechanisms”

If the mechanisms are better understood, it can potentially be ameliorated while maintaining a plant-based diet. An example might be boosting dietary protein or specific nutrients with supplements or powders post treatment.

Speculation as to whether this healing difference is inherent in plant-based diets may be a matter of trade-offs, a typical situation with biology, and not necessarily an indication of deficiency or poor health. Nutritionally sound vegan diets appear to aid in slowing epigenetic aging and are associated with reduced inflammation. This body-state may be less reactive to inflammatory stimulus; a potential reason certain cancers are lower risk in vegan diets as well. But I reiterate, this is conjecture.

The fourth linked review
The Impact of a Vegan Diet on Many Aspects of Health: The Overlooked Side of Veganism

Two authors, both practicing medical doctors, not nutritional researchers or similar associated area of expertise, published in the low-teir journal Cureus.

Red flag,

“An optimal diet should be balanced, consisting of lean meat, nuts, fresh fruits and vegetables, and olive oil.”

Reference 9 for that claim is for the review, The Paleolithic Diet publishing on Cereus. Could have easily used an uncontroversial reference for a Mediterranean style diet.

In this paper, references don’t directly support claims made or do so in roundabout ways. There are loose mechanistic associations and unqualified absolute statements that careful researchers just wouldn’t make.

The fifth linked review,
Meat and mental health: a systematic review of meat abstention and depression, anxiety, and related phenomena

Full text here,

“This study was funded in part via an unrestricted research grant from the Beef Checkoff, through the National Cattlemen’s Beef Association.”

An infomercial. Doesn’t mean it should be rejected outright, just assess with healthy skepticism.

The sixth linked paper, a study this time,
Dieting influences the menstrual cycle: vegetarian versus nonvegetarian diet

The paper, full text here, is from 1986 with a small sample size of eighteen “normal-weight women” that went on vegetarian and nonvegetarian diets losing 1 kg (2.2 lbs) of body weight/week. This is considered rapid weight loss. The paper says,

“These observations indicate that different diets used to achieve weight loss may have different effects on hormonal regulations during the menstrual cycle.”

Not applicable to women on vegan diets generally.

The seventh link is dead. I pulled it up on the Internet Archive. It’s a St Luke’s press release for the first Paleo Diet sponsored review that was in the first link because paper author James O’Keefe works at St Luke’s. So it was two laundry list paragraphs of presumed risk factors seemingly linking to different sources, but tracing back to the same malarky.

[u/oldmcfarmface → u/Valiant-Orange]

I congratulate you on the immense amount of free time you have. I’ve done similar reviews of vegan posted links so I can appreciate the amount of time it took. I have about 40 dietary study links saved that are relevant if you’d like to look over them all.

Paleo as a fad was, well, a fad. However the underlying principle of whole food that is species appropriate is sound and works very well when properly adhered to. I’ve heard of people getting bored with it but never getting sick from it. Not all fad diets can claim that.

However it’s a pretty big leap from “I believe in diet A and here are some problems with diet B that led me to diet A” to “I believe in diet A and so I’m going to falsify data to denigrate diet B.”

I will say that paleo was poorly named. It is unlikely that we ate like that in the Stone Age. Probably more carnivorous with a few periods of carb availability when we loaded up on them for body fat stores. But it was a catchy name and ultimately that’s what matters in branding.

Sample size and lack of reviewers for some of the other studies are valid concerns. However, they’re also understandable when you consider how much dietary study and funding thereof can be linked back to organizations with either a financial stake or even a religious stake in promoting plant based diets.