Epidemiological studies must always be approached with extreme caution. They are extremely difficult to design. Controls are always a result of compromise, and proper interpretation requires a comprehensive understanding of the design, and its limitations. kleinbl00 makes a good point that the study addresses the people with these diets, and not the diets themselves. Of course, the intention is that effects of the diets are detected in the statistics, but at best they cannot take us to the realm of causation. They can only hint to it to a degree, limited by the context of the design and the analysis.

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. We cannot state whether a causal relationship exists, but describe ascertained associations.

On a personal note, I have to say that when I have gone for extended periods without meat, I get a mild, yet genuine sense of euphoria when I do eat some. I expect that this is not the case for most people, however, whether due to my own dietary history, or my genetics, or both, I feel better when I have access to a moderate amount of meat.

Although the study matched for social economic status, it would be interesting to see if the results were similar for each of the three SES as they defined them.