Claim: The "Epic-Oxford Study" Showed that Vegans suffer from hip fractures


One study is typically cited as an argument that vegans have poor bone health, which showed a 43% increase in bone fractures for vegans in some cohorts.

Problems With This Argument

1. This paper accidentally makes the case for veganism

For a BMI higher than 22.5, vegans had a lower risk of fractures. This only represents 5/6ths of Americans. So this study should be cited to support veganism, unless you really cherry-pick the conclusions as carnists do.

2. This paper has serious methodological issues

The evidence is pretty weak and noisy:

  • Any such paper is showing correlation and inferring causation unless it has proper controls.
    • This paper didn't control for a number of deficiencies, for instance, Vitamin D intake, which is known to promote bone density.
    • The paper did not control for exercise or other lifestyle differences which increase balance and promote higher bone density or just put one in situations that reduce the risk of fractures.
    • The paper did not control for the number of children, which the Epic-Oxford group is known to have a large difference wherein the non-vegans had on average three times as many children as the vegans. Having children and breastfeeding them is known to increase bone density substantially amongst women. This study was 80% women.
  • The cohorts from whom the data of this were pulled go back as far as 1993 up to 2001. It's fair to say that the vegan diet in 1993 doesn't look a whole lot like all of the options available today fortified with the nutrients that we have in foods today.
  • The vegans in this study only ate 5% more fiber on average than their meat eating counterparts. This seems rather unlikely for typical vegans and typical meat eaters today.
  • BMI is known to decrease the risk of fracture in fat-padded areas (like hips) but not in unpadded areas, such as the wrist. Interestingly, this study shows that vegans had an increased risk of hip and not wrist fractures. Also, vegans have lower BMIs in this cohort. Thus this is a situation ripe for Simpson's paradox.
  • There was a stratification along BMI that they used that did not make much sense. Dr. Avi goes into the problems in depth in the deep-dive video. These additional stratifications do not seem to be based on known classifications of obesity. This leads one to p-hacking questions regarding the data and further exacerbates the probability that Simpson's paradox might come into play given the small sample sizes caused by over-stratification.

3. This argument disagrees with the scientific consensus

Given all the problems with this study and the noise in the data, it doesn't seem to support any significant conclusion regarding vegan bone health. Also, given the scientific consensus that all the other epidemiology supports veganism and lower risk of all the major disease factors, this would appear to just be a cherry-picking of the results.

4. Is this really believable

Is it really 43% more likely that vegans (especially modern vegans which this study is used to attack) are likely to break a bone given that milk and animal product substitutes are fortified to contain the same nutrients as their animal product counterparts? This same group of researchers found an increase in stroke risk amongst vegetarians and vegans. This just doesn't sound like a reasonable result.

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