Monday, April 7, 2014

Do vegetarians have poorer health?

I spend a lot of time, probably more than I should, skulking around in nutrition related forums where people share the successes and failures they've had with various weight loss plans and/or change of eating habits for a variety of health conditions.  If someone has had good success with one way of eating, chances are they will talk smack about other plans that are in opposition to their way of eating, and sometimes the points they are making are evidence based, sometimes they are not.  The last blog post I did was based on an article that a vegan friend was using to try to talk people out of their "paleo" diet; now it looks like the more omnivorous types could potentially fire back after reading an article like this one: Study: Vegetarians Less Healthy, Lower Quality of Life than Meat Eaters.  So do they have any evidence to truly turn the tables?  Let's apply the same Double X Double-Take to this news article.

1) Skip the Headline. Step away from the Appeal to Emotion Fallacy.

2) What is the Basis of the Article? This one was easy, click on the link in the article and ta-da!  Looks like we have access to the full article!  Now you get to read it, I'll wait.....
Did you see the "lots of people, lots of data, lots of analysis" to indicate that this is original research that has undergone a peer review.

3) Look at the words in the article.  You did read the article?  All the way through?  Including the part that has "limitations" printed in bold?  Here, I'll help:
"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 habits or if they consume this form of diet due to their poorer health status. We cannot state whether a causal relationship exists, but describe ascertained associations. Moreover, we cannot give any information regarding the long-term consequences of consuming a special diet nor concerning mortality rates. Thus, further longitudinal studies will be required to substantiate our results. 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, with giving them a clear definition of the various dietary habit groups." (Emphasis mine).
In other words, based on the people sampled we can't necessarily extrapolate to the larger population, correlation does not equal causation, we need more studies, and we can't rely of people's memory and subjective description of what they ate to determine treatment. 

4) Look at the original source of the information. As I said before, you will want to ensure that the journal and the article are peer reviewed and not just commentary by an "expert." Experts are human and can be prone to some not so scientific idea.  In this particular case a Google search about the journal indicates it is peer reviewed.

5) Remember that every single person involved in what you're reading has a dog in the hunt.  Once again, be careful that your speculations about what dog is in the hunt doesn't devolve into a variation of the ad hominem fallacy, so hold off on the inflammatory language for a bit.

6) Ask a scientist. Once again, I'm so glad you asked!  Some other points to ponder:
1) This study was done in Austria, and the news article was geared to people living in the United States.  Just because the majority of people in each country speak English doesn't mean they have the same eating habits and access to food. A typical vegetarian diet in Austria is likely different than in the US, I personally would have to research that more so I'm not going on assumptions.
2)  As it states above, we don't know if the vegetarians in this group were already in poor health before they changed their diet.  I can remember doing a rotation on the oncology ward as an intern and seeing people that were trying a variety of different diets, vegetarian and otherwise in the hopes that they would be able to cure their cancer.  Perhaps some of these people were having similar struggles with their physical and/or mental health and were making dietary changes that they thought might help.
3) The term vegetarian and vegan mean that you eschew animal flesh and all animal products respectively, these terms actually don't say anything about the quality of a person's diet.  As one friend of mine said about her husband, "He's more of a "sugartarian" than anything else..."  So perhaps these vegetarians weren't actually eating vegetables and were surviving on rice and chocolate and we can't extrapolate their data to a greater population of vegans who spend time planning their meals to include vegetables, soaking their beans to extract more nutrition, etc.  And before some of you start sputtering about how "that's not a vegetarian diet" you might want to study up on the No True Scotsman fallacy.  And remember, you can take just about any eating plan and make it unhealthy (I'm looking at you, people who survive on Atkins company diet products!)

So what do we do with this information?
1) Don't smoke (sound familiar?).
2) Moderate alcohol intake.
3) Include lots of vegetables and some fruit.
4) Don't over or under do your protein intake.

Edited to correct Australia to Austria thanks to alert reader Eve.  My spell-check needs spell-check.


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