Are vegan diets good for everything ... but bad for your bones?


Note: These results are especially important for vegan women but also quite important for vegan men.

A new study has just come out from some of the leading researchers investigating the effects of vegan diets on health worldwide.

There are two large studies on this planet that include several thousand vegans: the Adventist Health Study 2 (United States) and the EPIC-Oxford study (United Kingdom).

This new analysis - from the EPIC-Oxford study - has confirmed (some) what we already know about vegan nutrition and healthy bones, and it has confirmed something that we as vegans would really prefer not to hear.

Well, maybe we can do something about it, and in 10 years from now (or 5 years) we won't have to hear it again (?). Could be.

Now the bad news is: we really don't know what exactly we (as vegans) need to do to optimize bone health.

The good news is that maybe we do know. [I know, this may sound contradictory, but the difference is in the "maybe".]

Now the really bad news: vegans - in this study - had a higher risk of bone fractures (except for ankle fractures and rib fractures) compared to general meat eaters (people who ate land animals). And these results were quite clear. These results were clearest for women.

This does not necessarily mean that you or I as vegans have a higher risk of bone fractures. But it means that it would be a good idea to pay attention to the most important nutrients for vegans (some call the critical nutrients; we can also call the "good to be a little familiar with nutrients").

This study confirms some of the "healthy bones" rules:

  • Get enough calcium. [No, we do not need dairy at all.]
  • Get enough protein. [I know what you are going to say - don't say it.]
  • Avoid being underweight. [Better: aim for a BMI of at least 20.] (A BMI of at least 22 may be even better for your bones.)
This study also shows that it is not only calcium and protein that matter.

What this study does not confirm but is known anyway: if you want to optimize your bone health ...

  • Get enough vitamin D. (We need both enough calcium and vitamin D. Either or isn't good enough.)
  • Get enough vitamin B12.
  • Get enough zinc. (Eat legumes and nuts and seeds.)
  • Get enough vitamin K. (Good source: green leafy vegetables; vegans usually get enough.)
  • Eat a generally (more or less) healthy diet: a lot of fruit, vegetables, legumes, whole grains, nuts, seeds, and mushrooms if you like).
  • Get enough omega-3 fatty acids. (These may be important for your bones too.)
  • Get enough selenium. (But not too much.)
  • Exercise and keep your muscles strong. (You don't have to be a bodybuilder.)
  • Don't smoke.
  • Avoid alcohol excess.
  • Drinking tea may be good for your bones.

Note: It may be that African Americans have a lower risk of bone fractures. This may also apply to other Black people around the world, such as people of West African or East African descent. Black vegans should however follow the same "rules" above to optimize their bone health and to optimize in general. More studies are needed with vegans. And definitely more studies are needed with Black vegans. It might also be that people of East Asian descent have a lower risk of bone fractures, but this is much more uncertain. 

So, how can you manage to follow all of these rules? It isn't difficult, but it is not something that happens automatically either. Have a look at the important nutrients for vegans and good sources of these nutrients (same link as above).

Note that it may also be that some of the factors that make unhealthy diets are unhealthy may be - I know it sounds odd - good for your bones. Also note that - as the title of this post suggests - healthy vegan diets can likely lower disease risk in many areas (especially also diabetes and cancer). Some of the "bad factors" (including overweight and high blood sugar and blood insulin levels - which are really bad) may be good for your bones. This does not mean that we (as vegans) have to sit idly by and watch our bones crumble. We can pay attention to a generally healthy lifestyle and some key nutrients (again, same link as above). We "should" do so anyway for optimizing our vegan diet, and it will likely keep our bones strong too. See the bullet points above.



More technical info from this study (that you do not need to know):

BMI: "[...] the risk differences were likely partially due to differences in BMI [...]. 

A high BMI (overweight) likely decreases the risk of bone fractures, "particularly hip fractures". Possible reasons: "[...] the cushioning against impact force during a fall, enhanced oestrogen production with increased adiposity [fat tissue produces extra estrogen in men and women], or stronger bones from increased weight-bearing [your bones have to carry a higher body weight around]. 

But a high BMI is likely bad for your ankles and could increase the risk for "ankle fractures, possibly as a result of higher torques from twisting of the ankle in people with higher BMI."

Muscle strength: "In addition to BMI, previous studies have reported that muscle strength is an important risk factor which is protective against fall risk and subsequently fractures in older adults."


Who were the vegans in these study?

They were 1982 vegans from the UK (England, Wales, and Scotland) who were already vegan or near vegan at the beginning of the study (1993–2001; the start of the study wasn't the same for everyone) and (most of them also) at the second time point when they were asked about their diet (~2010).
So, these were the "90s generation or earlier" of vegans.

The vegans were on average about 39 years old [mean (standard deviation): 38.9 (13.6) years]

The vegans were a little bit more physically active than the non-vegans.

Only 51.9% of the vegans used dietary supplements, which may indicate that many of them had low vitamin B12 and/or vitamin D status (and maybe low selenium status).

23.8% of the vegan had a BMI of lower than 20 - more than in the other groups.

"Only" 34.4% of the vegan women had had (given birth to) any children - fewer women than in the other groups.

The average calcium intake of the vegans was 591 mg - which is quite/very low - but it also may have been underestimated. ("the role of calcium might have been underestimated due to measurement error")

The percentage of calories from protein in vegans was also lower: 13.3% of calories compared to 17% in meat eaters.

How many vegans were included in this analysis?

The number of vegans was 1,982.
"1982 vegans at baseline in analyses of total fractures"

How was the "vegan status" (or non-vegan status) assessed?

Participants were not just asked "Are you vegan?" This leads to a higher number of "fake vegans". Instead they were asked "How often do you eat ...?". Those who ate no or almost no meat, fish, dairy, and eggs were classified as "vegans". Honey was not considered and is quite probably irrelevant here in terms of bone health.

How were bone fractures assessed?

"Outcomes were identified through linkage to hospital records or death certificates until mid-2016."

How long did this study last?

Not the same for every participant: "an average of 17.6 years"

What about pescatarians and ovo-lacto-vegetarians?

In this study, pescatarians were called "fish eaters" and ovo-lacto-vegetarians were called "vegetarians". Fish eaters and vegetarians also had a highe risk, but the risk was clearly higher in vegans. Results, see below.  

Technical results:

"Compared with meat eaters, vegetarians (HR 1.11; 95% CI 1.02, 1.21) and vegans (1.50; 1.26, 1.78) had higher risks of total fractures after adjustment for confounders (Table 2 model 1)."

"The associations attenuated with additional adjustment of BMI (vegetarians—1.09; 1.00, 1.19; vegans—1.43; 1.20, 1.70), but remained clearly significant in vegans (Table 2 model 2, Fig. 1). The equivalent rate differences were 4.1 (0.8, 7.6) more cases in vegetarians and 19.4 (9.6, 30.9) more cases in vegans for every 1000 people over 10 years."

"The associations were attenuated further but remained significant in vegans with additional adjustment for dietary calcium (1.31; 1.10, 1.57, Table 2 model 3), total dietary protein (1.39; 1.16, 1.67, Table 2 model 4), or both dietary factors simultaneously (1.30; 1.08, 1.56, Table 2 model 5)."

"For site-specific fractures (Fig. 1 and Table 2), the largest magnitudes in risk difference by diet group were observed for hip fractures ["Fractures at some sites, especially at the hip, may also be more related to osteoporosis than fractures at some other sites, which might be more likely to be the result of violent impacts in accidents. We were unable to differentiate fragility and traumatic fractures in this study, since data were not available on the causes of the fractures."].

"Absolute rate differences of total and site-specific fractures by diet group in EPIC-Oxford": "Per 1000 people over 10 years" ... in vegans: "19.4 (9.6, 30.9)"; in vegan men: "6.5 (− 4.7, 21.3)" [not statistically significant]; in vegan women: "25.2 (12.1, 41.0)"; fish eaters: "− 2.4 (− 6.2, 1.8)". 

The lower rate in fish eaters here indicates that the causes of the higher risk in vegans may be related to micronutrients such as vitamin B12, vitamin D, omega-3 fatty acids [yes, not micronutrients technically speaking], zinc, selenium, ... [You do not need to eat fish.]

Regarding ankle fracture risk (which was not higher in vegans): Possibly the vegans in this study had harmful factors (micronutrient deficiencies (?)) and beneficial factors (less overweight, ...).
Ankle fractures: "[...] the results might reflect a counterbalance between a protective effect from lower BMI but higher risk due to lower intakes of nutrients related to bone health in the non-meat eaters."

"Summary of findings
Overall, vegans in this study had higher risks of total and some site-specific fractures (hip, leg, vertebra) than meat eaters. The strongest associations were observed for hip fractures, for which fish eaters, vegetarians, and vegans all had higher risks. These risk differences might
be partially explained by the lower average BMI, and lower average intakes of calcium and protein in the non-meat eaters. However, because the differences remained, especially in vegans, after accounting for these factors, other unaccounted for factors may be important."

"Table 5 Risks of total fractures by diet group, stratified by [.] sex [...] and BMI
[Vegan men:] "1.18 (0.85, 1.62)" [not statistically significant]
[Vegan women:] 1.53 (1.24, 1.88)"
[...]
[Vegans with a BMI smaller than 22.5:] "1.66 (1.32, 2.08)"
[Vegans with a BMI of at least 22.5:] "1.10 (0.80, 1.49)" [not statistically significant] 

"[...] possible effects of other nutrients or biological markers on fracture risks, for example circulating vitamin D, vitamin B12, or IGF-I, which may vary by degree of animal-sourced food intake."

If you want to get really technical, check out the tables in the "Supplementary information".

What have other studies on this subject shown?

"The only other studies which reported on risks of fractures by diet groups were one small prospective study in Vietnam of 210 women (105 vegans) which found no significant difference in fracture incidence (10 cases in total) between vegans and omnivores over 2 years, and one prospective study in India which reported a higher crude rate of stress fractures (604 cases in total) among 2131 vegetarian than 6439 non-vegetarian army recruits. Separately, previous findings from the Adventist Health Study 2, which has a large proportion of vegetarians, showed that participants who ate meat more than three times a week had lower risks of hip fractures (HR 0.60; 0.41, 0.87) than participants who ate meat less than once a week, while combined analyses of peri- and postmenopausal women from Adventist Health Study 1 and 2 found that participants who ate meat more than four times a week had lower risks of wrist fractures (HR 0.44; 0.23, 0.84) than participants who never ate meat [33], but these results cannot be used to infer risks in fish eaters, vegetarians, or vegans as separate diet groups."

Race and sex as potential factors

"As the study predominantly includes white European participants, generalisability to other populations or ethnicities may be limited [...]."

"In particular, because the EPIC-Oxford cohort consists predominantly of women (77%), further work should be conducted in cohorts with a larger proportion of men to explore heterogeneity by sex and to derive reliable sex-specific estimates."

Authors' conclusions

"Conclusions
Overall, we found that compared with meat eaters, vegans had higher risks of total, hip, leg, and vertebral fractures, while fish eaters and vegetarians had higher risk of hip fractures. These risk differences were likely partly due to their lower BMI, and possibly to lower intakes of calcium and protein. More studies are needed especially from non-European and contemporary populations to examine the generalisability of our findings and to explore possible heterogeneity by factors including age, sex, menopausal status, and BMI. Future work might benefit from examining possible biological pathways by investigating serum levels of vitamin D, vitamin B12, or IGF-1, or in assessing the possible roles of other nutrients that are abundant in animal-sourced foods."





Reference:

All quotations above are from this reference.
Tong, T.Y.N., Appleby, P.N., Armstrong, M.E.G. et al. Vegetarian and vegan diets and risks of total and site-specific fractures: results from the prospective EPIC-Oxford study. BMC Med 18, 353 (2020). https://doi.org/10.1186/s12916-020-01815-3