Is a Vegetarian Diet Really That Good for You?

The Truth Is Out There.
X-Files 1993-2002

Now, I'm game for just about anything that might make/keep me healthier and prolong (quality of) life, but I have to give you the following disclaimer:  I'm an omnivore, so you'll need to pry that well marbled USDA Prime rib eye from my cold dead hands.  But just yesterday, I stumbled upon a headline that read "Veggies Are Key to Long Life" and feared that my eating habits as I've known them for the past 5 decades were about to come to an abrupt 180o turn.  The referenced article was a prospective cohort study published early online in JAMA Internal Medicine (aka Archives of Internal Medicine) in which the authors concluded that vegetarian diets are linked to lower all-cause mortality & some cause-specific mortality.  But just like Michael Douglas' proclamation earlier this week that oral sex begat (his) oral cancer, the science isn't always so clear cut.

To arrive at their conclusions, the authors followed 73,308 Seventh Day Adventists  for close to 6yrs.  While their average age was 56-59yo, their average body mass index was only 24-28kg/m2, much less than the average American these days, which might bring into question the generalizability of the results.  Nonetheless, they were able to conclude that any vegetarian diet was associated w/12% lower all-cause mortality compared to non-vegetarian adherents (like myself).  Interestingly, the results for ischemic heart disease mortality, cardiovascular disease mortality, and cancer mortality did not reach statistical significance, while "other mortality" barely did at 15% lower risk.

However, if you looked at female vegetarians (which I'm definitely not either), there was no statistically significant reduction in either all-cause or disease specific mortality.  Male vegetarians did demonstrate 18% lower all-cause mortality and 29% lower cardiovascular disease mortality.  In case you're wondering, ischemic heart disease refers exactly & only to heart disease while cardiovascular disease includes carotid artery disease & stroke, too.

Now, little did I know, but among vegetarians, you can further sub-classify yourself as vegan, lacto-ovo-vegetarian, pescovegetarian, and even semi-vegetarian.  Well, the authors did, any way, lumping those who ate non-vegetables less than once per month as vegans; lacto-ovo as those who consume eggs & dairy more than once a month but no other non-vegetables; pesco- as those who consumed fish at least once a month but any other meat less than once a month; semi- as those who consumed fish & non-fish meats more than once a month but no more than once a week.  Got it?  Sound a bit like a slippery slope, right?  

Well, if you're only as strong as your weakest link, it turns out that sub-classifying vegetarians reduced statistical significance such that only pesco-vegetarians achieved 19% lower all-cause mortality & 35% lower ischemic heart disease mortality.  All others were unable to reach statistical significance.  And remember that slippery slope, while vegan, lacto-ovo & pesco tended to liver longer (albeit w/o statistical significance), semi-vegetarians showed worst statistics.

Yes, I remember that quote about "Lies, damned lies & statistics" popularized by Mark Twain.  But in this instance, that "faulty" headline doesn't nearly capture the complexity of the data.  It's unfortunate that we can't summarize new findings in 15 second sound bites or 140 characters.  I guess that means I can go back to gnawing on some gristle for a while longer.

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