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Monday, May 12, 2014

‘Vegetarians less healthy than meat-eaters” study debunked

downloadAn article was posted in the dailymail about Vegetarians supposedly being less healthy than meat eaters, and having a lower quality of life.
Conclusions of their study: vegetarians visit their doctors more often, are more prone to allergies, cancer, heart problems and bad mental health. They experience more depression and anxiety.
Actually, some other researchers already took a look before me. What did they get analyzing the data? Almost exactly the opposite results. Read it here:
“Our results show that a vegetarian diet is associated with a better health-related behavior, a lower BMI, and a higher SES. Subjects eating a carnivorous diet less rich in meat self-report poorer health, a higher number of chronic conditions, an enhanced vascular risk, as well as lower quality of life. In conclusion, our results have shown that consuming a diet rich in fruits and vegetables is associated with better health and health-related behavior. Therefore, public health programs are needed for reducing the health risks associated with a carnivorous diet.
To my understanding of serious scientific, if someone get results A and !A regarding to the same data-source, then there seems to be something wrong with the methods. Under that conditions it seems very unclear (or even more than that to me), if the results can have a value at all. ”

Also some extra notes, the sample sizes were way off! So this is why the first study gave bad results for vegetarians:
comparing 2.2% vegetarians vs. 23.6% consuming a carnivorous diet rich in fruits and vegetables vs. 48.5% eating a carnivorous diet less rich in meat, and 25.7% consuming a carnivorous diet rich in meat).
Only 2.2 % vegetarians!
The next study showing vegetarians are healthiers, actually matched the groups to be equal . “The total number of analyzed subjects comprised 330 vegetarians (1) who were each matched to 330 subjects consuming a carnivorous diet rich in fruits and vegetables (2), 330 individuals eating a carnivorous diet less rich in meat (3), and 330 subjects consuming a carnivorous diet rich in meat (4).
Some more comments on the paper:
Then these results are devoid of any generalizable data. If your goal was to subtype your prior work, the conclusions on this paper should be “rich young female vegetarians may be sicker”. At best, this would suggest teen-to-30-something women are not the best at both avoiding meat and eating a balanced diet; instead we get comments about public health measures that are needed to prevent the harmful effects of eating vegetables. Additionally, if you wanted to ‘match’ your subjects, why have such a wild difference in the groups? Table 1 shows a range from 15yo poor boys to 80yo middle class females. With only 330 in each group, this is hardly ‘matched’ by ‘certain socio-demographic characteristics’ and not compared to the 15K subjects study reflecting the general population. If you wanted to subgroup, you should have done so with each tier presented in Table 1 – ie vegetarianism impact on 15-19yo, low income only, females only, etc. Or you should have age-adjusted, multi-varient adjusted your prior paper. Instead you simply lowered your power and reran your prior analysis.
I agree fully with DrSiebler that your papers are arguing the exact opposite thing. While I find your explaination somewhat acceptable, your discussion and abstract never bring up your prior work and never outline such nuance. Given the media’s love of jumping on hyperbolic nonsense, suggestions that ‘vegetarianism causes cancer’ are unethical if you are going to put them out there without any context. What would you want people to take away from both papers in total? Eat vegetarian or not? Limit meat or not? Only eat vegetarian if you are not a rich Australian women under 50? This is what I think you have not answered from DrSeibler – what “public health measures” are you advocating for in paper A and paper !A?;jsessionid=6101CAEBEB2483F1D53C00146A047337?root=78839

The authors of the first study say:
 In our opinion, it seems not far to seek that persons with worse health consume a vegetarian diet because they try to develop a better health and eating behavior, and not the opposite, that a certain diet (vegetarian) leads to worse health. We therefore state in our discussion that we can neither say anything about causes or effects, nor about long-term consequences. Moreover, we say that further studies are needed to analyze nutritional habits and their association with health.
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