Jump to content
Dean Pomerleau

Why Don't UK Vegans/Vegetarians Live Longer?

Recommended Posts

Another study, this one a large study from Australia, confirms that the vegetarian mortality advantage is due to confounding with other lifestyle factors:
 

 

Evidence to date suggests that vegetarians tend to have lower mortality rates when compared with non-vegetarians, but most studies are not population-based and other healthy lifestyle factors may have confounded apparent protective effects. The aim of this study was to evaluate the association between categories of vegetarian diet (including complete, semi and pesco-vegetarian) and all-cause mortality in a large population-based Australian cohort... of 267,180 men and women aged ≥45years [ mean age: 62.3years, 46.7% men] in New South Wales (NSW), Australia ... categorized into complete vegetarians, semi-vegetarians (eat meat≤once/week), pesco-vegetarians and regular meat eaters. ...

[Vegetarians were less likely to smoke, drink >14 drinks per week, or be sedentary or overweight/obese]. Following extensive adjustment for potential confounding factors there was no significant difference in all-cause mortality for vegetarians versus non-vegetarians [hr hr=1.16 (95% CI 0.93-1.45)]. There was also no significant difference in mortality risk between pesco-vegetarians [hr hr=0.79 (95% CI 0.59-1.06)] or semi-vegetarians [hr hr=1.12 (95% CI 0.96-1.31)] versus regular meat eaters.
 
We found no evidence that following a vegetarian diet, semi-vegetarian diet or a pesco-vegetarian diet has an independent protective effect on all-cause mortality. [MR: Actually, even on crude analysis, there was no real suggestion of lower mortality in vegetarians, whereas in the fully-adjusted model there was a suggestion of lower mortality in the pesco-vegetarians —Table 4].


Reference
1: Mihrshahi S, Ding D, Gale J, Allman-Farinelli M, Banks E, Bauman AE. Vegetarian diet and all-cause mortality: Evidence from a large population-based Australian cohort - the 45 and Up Study. Prev Med. 2016 Dec 29;97:1-7. doi: 10.1016/j.ypmed.2016.12.044. [Epub ahead of print] PubMed PMID: 28040519.
 

Share this post


Link to post
Share on other sites

 

Another study, this one a large study from Australia, confirms that the vegetarian mortality advantage is due to confounding with other lifestyle factors:

 

 

Evidence to date suggests that vegetarians tend to have lower mortality rates when compared with non-vegetarians, but most studies are not population-based and other healthy lifestyle factors may have confounded apparent protective effects. The aim of this study was to evaluate the association between categories of vegetarian diet (including complete, semi and pesco-vegetarian) and all-cause mortality in a large population-based Australian cohort... of 267,180 men and women aged ≥45years [ mean age: 62.3years, 46.7% men] in New South Wales (NSW), Australia ... categorized into complete vegetarians, semi-vegetarians (eat meat≤once/week), pesco-vegetarians and regular meat eaters. ...

 

[Vegetarians were less likely to smoke, drink >14 drinks per week, or be sedentary or overweight/obese]. Following extensive adjustment for potential confounding factors there was no significant difference in all-cause mortality for vegetarians versus non-vegetarians [hr hr=1.16 (95% CI 0.93-1.45)]. There was also no significant difference in mortality risk between pesco-vegetarians [hr hr=0.79 (95% CI 0.59-1.06)] or semi-vegetarians [hr hr=1.12 (95% CI 0.96-1.31)] versus regular meat eaters.

 

We found no evidence that following a vegetarian diet, semi-vegetarian diet or a pesco-vegetarian diet has an independent protective effect on all-cause mortality. [MR: Actually, even on crude analysis, there was no real suggestion of lower mortality in vegetarians, whereas in the fully-adjusted model there was a suggestion of lower mortality in the pesco-vegetarians —Table 4].

 

Reference

1: Mihrshahi S, Ding D, Gale J, Allman-Farinelli M, Banks E, Bauman AE. Vegetarian diet and all-cause mortality: Evidence from a large population-based Australian cohort - the 45 and Up Study. Prev Med. 2016 Dec 29;97:1-7. doi: 10.1016/j.ypmed.2016.12.044. [Epub ahead of print] PubMed PMID: 28040519.

 

 

 

[MR: Actually, even on crude analysis, there was no real suggestion of lower mortality in vegetarians, whereas in the fully-adjusted model there was a suggestion of lower mortality in the pesco-vegetarians —Table 4]

 

Honest question: is there some way this is meaningful at all ("suggestion of lower mortality in pesco-vegetarians")? I mean, if they felt it reached any kind of significance, wouldn't they mention it? I ask, because I've adhered to pesco-vegetarianism in the hope that it *might* offer some kind of health advantage, while fully recognizing that it may not. 

Share this post


Link to post
Share on other sites

It is a reasonable assumption, highly likely to be true, that vegetarians - of whatever variety, semi, pesco etc. - eat more in the way of F&V than meateaters. One reads studies that go back and forth about how many portions of F&V is optimal to consume, but whatever it is, it's usually framed as "more is better" up to 7-9 or so per day. In any case, I find it interesting that despite vegetarians likely consuming more portions of F&V than meateaters, have no different incidence of all-cause mortality in the time frame studied. So why should anyone make an effort to eat more F&V than the average meateater? That's another way of saying that not only is red meat consumption not a negative, but F&V consumption is not a positive wrt. health outcomes - a double whammy of sorts.

Share this post


Link to post
Share on other sites

Yet another review of observational studies, very recent, can be found in this article (most probably already cited by Al PAter).

Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies

It is interesting since they discuss, even as it has been discussed here, the previous metanalysis portrayed by Dean:

 

t8mbRVO.png

 

I'll be back on this. Conclusions are the same as reported by Michael, apparently. Counterintuitively, more favourable health parameters do not translate usually to more favourable, significant hazard ratios (except for ischemic heart disease and cancer).

Edited by mccoy

Share this post


Link to post
Share on other sites

Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies

Crit Rev Food Sci Nutr. 2017 Nov 22;57(17):3640-3649. doi: 10.1080/10408398.2016.1138447.

 

Full-text link:

 

https://www.researchgate.net/publication/293329136_Vegetarian_vegan_diets_and_multiple_health_outcomes_A_systematic_review_with_meta-analysis_of_observational_studies

 

 

 

This is the same study already discussed by Dean P.  et al.

https://www.crsociety.org/topic/11450-why-dont-uk-vegansvegetarians-live-longer/?do=findComment&comment=15310

Edited by Sibiriak

Share this post


Link to post
Share on other sites

Sibiriak, your search resulted in the same publication I linked, so we can assume that's the more recent one, presently.

Edit: yes, it's the same publication posted by Dean and referred to the e-pub ahead of print, I didn't realize it previously.

 

Some abstracts since this appears to be the more comprehensive study available to date.

 

 

 

Our search yielded a total of 10,516 unique citations. After review and excluding duplicate reports we identified 433 citations as potentially relevant for the analysis. Of these, 325 were excluded after full-text reviews for the reasons described in Figure 1. Overall, a total of 108 articles were finally included in the meta-analysis (Figure 1).

 

Basic health parameters such as BMI, lipid profile, blood glucose appear to be more favourable in vegetarians/vegans, in a statistically very significant way (very low p-values), except a couple of values in the vegan group (HDL cholesterol, Trygs). 

 

This is the vegetarians group

post-7347-0-80394600-1498114276_thumb.jpg

 

A possible explanation of the disappointing results (for vegetarians) of the matanalysis

 

 

The overall analysis among prospective cohort studies documented a 25%-reduction of incidence and/or mortality from ischemic heart disease (Ashen, 2013) but not of incidence and/ or mortality from total cardiovascular and cerebrovascular diseases, and an 8%-reduction of incidence of total cancer but not of mortality from cancer when vegetarians were compared to nonvegetarians. These results, although partly surprising, could be explained by the fact that incidence and mortality are 2 very different outcomes, with cardiovascular and cancer mortality being greatly influenced by the treatment approaches. Moreover, the overall analysis in the cohort studies reported no significant association with specific localizations of cancer disease, such as incidence and mortality from breast cancer, as well as incidence of lung, colon-rectum and stomach cancer. This fact can be explained by the low statistical power, due to a low number of studies evaluating this aspect and a low sample size.

 

Then some possible biases are listed

 

 

However, our study suffers from some limitations, which are intrinsic of the studies included in the overall analysis. For instance, we could not analyze an important datum such as the duration of adherence to the vegetarian or to the vegan pattern in the different cohorts. Indeed, only one study explicated this finding that is extremely relevant for understanding the relationship with mortality and incidence of disease. In addition, the definition of the control group, i.e., those following an omnivorous diet was not really well-defined, including in some cases subjects consuming a high intake of meat and meat products and in other cases subjects with a reduced consumption of meat and derivatives. A final potential weakness is the accuracy of the assessment of vegetarian and vegan status. There are several slight differences in the population of vegetarians throughout the world, and the possibility that some studies could have included vegetarians and vegan altogether cannot be ruled out.

Edited by mccoy

Share this post


Link to post
Share on other sites

OK, sorry for the above multi-posting but I was multi-tasking and was not allowed to cancel the junky posts, I realize the system might just not allow to do that.

 

I reviewed all the discussions and I'd like to see if it is possible to reach a reasonable conceptual framework on the issue.

 

Facts:

 

  1. The most recent and allegedly most comprehensive metanalysis on the issue, the Italian Dinu et al., 2017 study, illustrates that all-cause mortality is not significantly different in vegetarians, whereas ischemic hearth disease and cancer incidence are significantly better (especially so ischemic hearth disease). Ditto for vegans, except cancer incidence, although the vegan sample is admittedly small
  2. The same recent and comprehensive Dinu et al., 2017 metanalysis suggests that vegetarians exhibit more favourable basic health parameters such as BMI, lipid profile, blood glucose 
  3. Since basic health parameters are statistically significantly better, it logically descends that vegetarians should exhibit a statistically significant better health than omnivorous people
  4. Vegetarians and vegans have no statistical mortality advantage, which can be explained by medical interventions for example, which avoid across the board an higher mortality but might seriously compromise quality of life.
  5. The metanalysis suffers some inherent limitations, which makes it not as robust as it may seem considering the number of studies examined and the screening strategy employed.

My personal bottom line is that, well, an admittedly imperfect metanalysis says that vegetarians/vegans have not better mortality hazard than omnivorous, but they undoubtedly have an overall health advantage (although the health parameters are really basic).

 

I might just be happy with that, considering that other factors (which have been filtered out) may overwhelm the mortality scenario, like driving accidents, smoke, suicide and so on. The fact that vegetarians smoke less and maybe are happier and commit less suicide is amenable to other considerations.

 

The Australian study just would confirm that vegetarians in Australia have no mortality benefit. It may contain though the same inherent limitations of the British study, even though the data collection seems reasonable to me.

 

The above having been said, the well-informed and consistent vegetarians/vegans might even, like Dean has proposed, discard the recent meta-analyses on the base that they are not representative of such a sub sample of strict, rigorous, nutritionally educated subset. Such a subset would be more correctly represented by the subset of Adventist vegetarian and vegan cohorts, if we can reasonably rule out significant biases in those studies. This proposition seems totally logic and devoid of personal bias to me, providing of course we can assign a sufficient reliability to the Adventist study (I did not examine this aspect).

 

And of course a more drastic but totally acceptable approach would be to ignore all such epidemiological studies, given the impossibility to avoid limitation and biases and reach a satisfactory degree of reliability.

Edited by mccoy

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×