Snake oil merchants

(versión en español: pinchar aquí)

Last October it was published (in the Baylor University Medical Center Proceedings) an article criticizing gluten-free diets, and more specifically the book “Grain Brain” by Dr. David Perlmutter. The article’s title is “Gluten sensitivity: new epidemic or new myth?”.

The first thing that attracted my attention is that when they write about Dr. David Perlmutter they do not refer to him as a “Medical Doctor”:

In the book Grain Brain, for example, the author, David Perlmutter, lists Dozens of diseases and symptoms That I factotum believes are all related to gluten sensitivity and May just thus be prevented us or cured by a gluten-free diet.

Surprising, to say the least, the disrespect to Dr. Perlmutter. Then they compare the oratory of his book with the “snake oil” merchants of generations ago. I wonder what motivates the insults.

And they compare those times with the “placebo-controlled, randomized clinical trials”, which they call “the mainstay of proof of efficacy and safety in our modern era of health care”. Then they embrace the task of showing that diets high in carbohydrates are not bad. How would they do that? Logic says they would cite “placebo-controlled, randomized clinical trials”, they ones they just praised as the highest scientific proof. But they don’t! They start citing a systematic review of prospective cohort studies, then they refer to a prospective study and then cite another meta-analysis of several prospective cohort studies. In short: rubbish. That is an observational study as a scientific evidence. But wait! then they comment a randomized trial, which they say shows that a diet low in fat, using plant-based foods, reduces the cardiovascular risk. A quick review of that article reveals that the study is based on a vegan diet. What proof is that? How can they pretend to extrapolate the results of a vegan diet to other diets high in carbohydrates? Anyway, I decide to analyze the study. Its main features are:

  • There was no placebo group, therefore it is not a randomized clinical study with placebo group
  • The participants had diabetes type II, so the results in any case can be extrapolated only to people suffering from this condition
  • It is not a controlled study. No one knows what the control group ate (“Individuals at control sites made no dietary changes, were given no dietary guidance and no additional food was made available in those sites.”). That means we are comparing the vegan diet with “don’t-know-what” diet”. Awesome.
  • The vegan diet resulted in a reduction of the HDL and an increase of the triglycerides. That means the cardiovascular risk worsened with the vegan diet, compared with an unspecified diet. I can’t see reasons to celebrate.
  • The article’s authors emphasize that the HbA1c and LDL were reduced. In view of the changes in both HDL and TG, the profile of the LDL particles probably worsened, becoming denser and smaller (see). Don’t the authors know that LDL is a bad risk indicator, outperformed by the HDL and TG (see), and that, in any case, it’s the type and quantity of LDL particles, and not the concentration, what counts? As for the glycated hemoglobin, it seems logical to improve it if you remove the refined grains from the diet, even if you consume whole grains. That would not mean that whole grains are healthy, just that they are better than refined grains for blood glucose control. But saying that the control group consumed refined grains, is just a guess, because no one knows what they ate. In any case, this article doesn’t show that eating whole grains is better than eating no grains. It doesn’t even show that whole grains are better than refined grains.
  • Besides the above, LDL was not measured (except in extreme cases), but calculated with the Friedewald equation

As summary, for people with type II diabetes a vegan diet may worsen their cardiovascular risk when compared with eating “don’t-know-what” diet. What a great result! Even if the vegan diet performed better than the “don’t-know-what” diet, it would be irrelevant.

What did they try to show citing this article?

Would you say that this study shows that diets high in carbohydrates are not bad for our health? If these two people took the time to write an article that criticizes gluten-free diets, and all they are able to use are the referred “evidences”, which they say are “high level”, who are the “scientists” whose oratory is reminiscent of the snake oil merchants?

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