A CBS Atlanta story is promoting a poorly designed cross-sectional study from Austria as though it is the best evidence we have regarding vegetarian diets.
As I hope most of my readers know, I do not quickly dismiss a study just because I don’t like the results.
In 2007, when EPIC-Oxford found a higher risk of fractures among vegans who didn’t get over 525 mg of calcium day, rather than finding some limitation of the study which is always possible to do, I started emphasizing that vegans need to get more than 525 mg of calcium per day. There are many other examples.
So when I say a study whose results I don’t like is pretty much useless, it’s because the study is pretty much useless and not because I don’t like the results.
In December 2013, a cross-sectional study from Austria aiming to compare the health status of vegetarians to other diet groups was released (1), and I wrote about it in the post Austrian Vegetarians: Good News? It was, with all due respect to the researchers, one of the most oddly designed studies I have seen to describe vegetarians.
In the study, the diet categories were:
– Vegetarian (vegans, lacto-ovo-vegetarians, and pesco-vegetarians)
– Carnivorous diet rich in fruits and vegetables
– Carnivorous diet less rich in meat
– Carnivorous diet rich in meat
The researchers didn’t define these categories for the participants when they were asking them which category they belonged to.
The researchers also created a number of health indicators that I didn’t feel confident in even though they concluded that vegetarians had the best self-rated health and the lowest incidence of chronic conditions.
Then on February 7 2014, another paper from this same study was published (2). I read the abstract and saw that their conclusions were somewhat different in the more recent paper, and less favorable to vegetarians, but given the boondoggle that I considered the study to be, I put it aside with no intention of doing another write-up.
Fast forward to April 1, when an article about the February paper was published on CBSlocal.com (Atlanta), Study: Vegetarians Less Healthy, Lower Quality Of Life Than Meat-Eaters. This CBSlocal article made the rounds quickly and so I decided it was time to comment on the study.
My criticisms of the February paper are pretty much the same as for the one from December. However, the February paper had more information.
With the diet categories so poorly designed, it’s surprising that they found a number of statistically significant differences in disease incidence between the groups. In comparing the vegetarian group to the carnivorous diet rich in meat group, the vegetarians had a higher rate of allergies, cancer, and mental illness, while the rich meat group had a higher rate of urinary incontinence. Asthma, diabetes, cataracts, hypertension, heart attack, stroke, osteoporosis, among other diseases, were not significantly different across diet groups.
As for the self-reported quality of life scores, some of the information didn’t match between the two papers; for example, the December paper lists the chronic conditions score for vegetarians as 1.45 while the February version lists it as 1.29 (lower is worse), a meaningful difference in their scheme.
Enough said about the specifics of this study, other than that the February paper is available for free at the link from the citation below, so if you want to check it out on your own you can. But quibbling over the details of either of these papers is fairly pointless. As the authors state in their relatively long section on the limitations of their study (2):
“Potential limitations of our results are due to the fact that the survey was based on cross-sectional data. Therefore, no statements can be made whether the poorer health in vegetarians in our study is caused by their dietary habit or if they consume this form of diet due to their poorer health status.”
They also bring up my earlier criticism:
“Further limitations include the measurement of dietary habits as a self-reported variable and the fact that subjects were asked how they would describe their eating behavior, without giving them a clear definition of the various dietary habit groups.”
The study from Austria, with all it’s limitations, is one thing. But the article from CBS Atlanta (link), adds insult to injury.
The CBS Atlanta article suggests that the Austrian study indicates causation (“But the vegetarian diet…carries elevated risks of cancer, allergies and mental health disorders”) and ignores a huge body of much better evidence regarding vegetarian diets, making it seem like this Austrian study is all we have to go on.
In fact, as most of my readers probably already know, much better studies following vegetarians over time have shown them to have equal or better health than regular meat-eaters in a number of diseases. You can read all about those studies in the VeganHealth.org section, Research on Vegetarians and Vegans.
For those not familiar with this research, I will point you to the fact that vegans have been found to have only a fraction of the risk of developing type 2 diabetes compared to regular meat-eaters (Type 2 Diabetes and the Vegan Diet).
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1. Burkert NT, Freidl W, Großschädel F, Muckenhuber J, Stronegger WJ, Rásky E.
Nutrition and health: different forms of diet and their relationship with various
health parameters among Austrian adults. Wien Klin Wochenschr. 2014
Feb;126(3-4):113-118. Epub 2013 Dec 17. | link
2. Burkert NT, Muckenhuber J, Großschädl F, Rásky E, Freidl W. Nutrition and Health – The Association between Eating Behavior and Various Health Parameters: A Matched Sample Study. PLoS One. 2014 Feb 7;9(2):e88278. | link