Chris Masterjohn has quite an important blog post about dietary dogma and why we should not be dogmatic. I recommend everyone read it.
But it did bring up an important idea on which I would like to elaborate. Where do our dietary dogmas come from, and how are they justified?
Is our dietary dogmas based on religion? Religion often offers an absolute standard for Why We Do What We Do. Dietarily speaking, do we eat Halal (Islam), Kosher (Judaism), lacto-ovo vegetarianim (7th Day Adventist), or abstain from coffee, tea, tobacco, alcohol, eat lots of wheat but eat meat sparingly (Mormon)? Religion uses some form of revelation to justify the dietary dogma, but this begs an important question: whose source of revelation is the "right" one? This is not a question that can be answered empirically. The religious adherent is backed up to the wall of faith, and there she or he must make a stand.
Is the dogma based on science? Scientific justification is not as solid as many suppose. For example, here is a question with no answer, despite decades and perhaps centuries of trying: what is the demarcation between "science" on the one hand and "non-science" on the other? We almost venerate science by assuming it is a special, different sort of knowledge, containing Truth. So non-science must equate to non-Truth. If this is so, then it is important to know the dividing line between "science" and "non-science." Is it possible to come up with a definition of science that gives "scientific" knowledge a privileged status over "non-scientific" knowledge, one that no one can poke holes in? This is not a trivial question.
For a really good primer on this "problem of science," read the book, What is This Thing Called Science? by Alan Chalmers. This is a philosophy of science primer often used in college courses and remarkably easy to read. He starts with logical positivism and in a balanced fashion looks at each of the definitions of science, then pokes holes in them all. He does this for falsificationism, Kuhnian paradigms, research programs, methodological approaches, Bayesian approaches to science, scientific realism, new experimentalism, and even Feyerabend's "anything goes" view of science. He leaves us with the distinct impression that science, as a justification for anything, is built on a foundation of sand. The history of scientific progress is actually quite messy, and the sociology of science has a lot to say as well. For example, how objective can a scientist be, when scientific progress is dependent on a funding source and when tenure depends on getting the right type of articles published in the right outlets?
When people realize they cannot draw the demarcation between science and non-science, they often retreat to a Justice Stewart Potter type of defense: "I can't define it, but I know it when I see it." This is also an indefensible way of justifying scientific knowledge, as it is open to subjective judgment.
Then there is the "it works" defense. I have used this one to defend low carb diets, as it has unquestionably worked in my case. But I am a sample size of one; does it "work" for everyone? Do I have a right to project my success onto others? Is it possible that it won't work for someone else? Also, can I conceive that it might stop working for me in the future? So this is an equally poor justification. Weight Watchers also worked for me, but I never want to go back to that plan. For that matter, starvation will also work to control diabetes and to lose weight. But is it wise?
So why do we believe that low carb is "The One True Way of Eating?" Because it works? Because science tells us so? Because we have faith in it? Because an authority figure wrote a book about it?
Without critically thinking through some of these issues, I might as well check my brain in at the door and stop learning new things. Follow, but not question, the "received" wisdom of the Low Carb Elders. When they have spoken, the thinking has been done. Line up and follow, or else you're an infidel!
Or learn wisdom and seek out that which is good, that which works for you. Recognize that there is more to learn and discover out there, and keep an open mind. Challenge your beliefs; it will make your rationale for following your particular dietary plan stronger.