In 2014 researchers from the Medical University of Graz published a study The Association between Eating Behavior and Various Health Parameters which concluded in the abstract:

... a vegetarian diet is associated with poorer health (higher incidences of cancer, allergies, and mental health disorders), a higher need for health care, and poorer quality of life.

The study was subsequently reported on by the media with titles like "Vegetarians are 'less healthy and have a lower quality of life than meat-eaters" (independent.co.uk).

The article Are Vegetarians Less Healthy than Meat-Eaters? (theveganrd.com) is pointing out some issues with the study, but I wanted to know if other scientists have also pointed out some issues with the study, or if this is the accepted wisdom today.

Any credible links discussing the study (in lay terms) would also be welcome.

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    Look at the power of the study - that study had a n of just 1300 compared to studies of Blue Zone populations, like the Adventist health studies that have many thousands... – DoctorWhom Nov 15 at 5:43
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    I think the study's conclusions are overreaching, especially given its low quality (small sample size, etc). This study isn't accepted wisdom by any means and the vegan site raised some valid concerns. – Carey Gregory Nov 15 at 5:43
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    You seem to not be aware how science works. One study is not the same thing as "accepted wisdom". Also, practically every study has issues. Basically, it is never a case of "study said it -> it is true" (and generalizable!) or "study said it, but it has issues -> it is untrue, or study is irrelevant to truth". – rumtscho Nov 16 at 15:23
up vote 6 down vote accepted

The study is still "valid" in the sense that PLOS One has not retracted the publication. This means the work was done in good faith and the methodology is acceptable, but it does not necessarily mean the results should be accepted as truth. To assess validity of the study we should look at comments and criticisms.

Because of the significant media attention, the UK NHS (National Health Service) published a detailed assessment of the study which is written in layman's terms. In addition, the lead author of the study made some follow-up comments in the reader notes on PLOS One which I'll refer to.

Limitations and Concerns of the Study

  • The design of the study can only show association, not causality. It is equally likely that people with health problems adopted a vegetarian diet.
  • Because of limited sample size, the authors grouped together 25 vegans, 126 lacto-ovo vegetarians, and 179 pescetarians and labelled them all as "vegetarians".
  • The study sought to identify relationships on many variables, such as prevalence of cancer and depression, but the sample size was too small to produce statistically significant results for this kind of multivariate analysis.
  • The presence of disease was not medically verified, so the results could equally be explained if vegetarians were more likely to be hypochondriacs (people who are abnormally anxious about their health).
  • The study includes only an Austrian sample who may have different dietary, health and lifestyle habits from other countries.

Perspectives

UK NHS (National Health Service)

https://www.nhs.uk/news/food-and-diet/vegetarians-have-poorer-quality-of-life-study-claims/

Despite the media headlines, the results from this Austrian cross sectional survey provide no proof that vegetarians are in poorer health than meat eaters.

Lead Author

Nathalie T. Burkert, March 2014

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.

According to the question if

Vegetarians are 'less healthy and have a lower quality of life than meat-eaters'

I'll just leave here the reports of experts from the International Agency for Research on Cancer (IARC), operating at the WHO, from 2015 and 2018 (after verification of over 800 tests over the last two decades), who clearly indicate that:

intake of 50g of processed meat and read mead a day can be linked with cancer development (processed ie through salting, curing, fermentation, smoking or other processes that improve taste and support maintenance) increases the risk of cancer development by as much as 18%.

https://monographs.iarc.fr/wp-content/uploads/2018/06/mono114.pdf

American Dietetic Association and Dietitians of Canada about vegetarian diets (older one:from 2003), points out:

Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life-cycle including during pregnancy, lactation, infancy, childhood, and adolescence. Vegetarian diets offer a number of nutritional benefits including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fibre, magnesium, potassium, folate, antioxidants such as vitamins C and E, and phytochemicals. Vegetarians have been reported to have lower body mass indices than non-vegetarians, as well as lower rates of death from ischemic heart disease, lower blood cholesterol levels, lower blood pressure, and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer.

https://www.ncbi.nlm.nih.gov/pubmed/12826028?dopt=Citation&fbclid=IwAR38NrVULMax9CHsf0m-BHaJWekJjnhZCBMg7077MGn0jx-KMUX9UxUDxug

So the statement which was closing up the article you mention above (independent.co.uk) says:

There needs to be further study done before this question can be answered.

Thinking about cancer, I find the research of IARC as an answer.

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