Fact Checking a Perlmutter Interview

Nutritional pseudoscience predominates in part because it is too easy for self-proclaimed experts to get away with saying anything they want without producing evidence. Such is the case for “Grain Brain” and “Brain Maker” author Dr. David Perlmutter, who claims – to paraphrase – that grains cause such wide-ranging diseases as Alzheimer’s, Parkinson’s, ADHD, autism, multiple sclerosis, diabetes, and cancer, to name just a few.

Perlmutter has a long history with pseudoscience- detailed in this great article by Dr. Alan Levinovitz. One of the most enlightening parts is that Perlmutter claims a treatment for Parkinson’s works when a study in which he is the last author shows that it doesn’t. Read the article, then Alan’s great book – the perspective of nutrition from a scholar of religion is unique and I found it refreshing. If you want a taste, listen to an interview of him here.

It takes enormous resources to thoroughly fact check such claims, so it is rarely done. In the end, it usually doesn’t inflict any consequence to the person making the claims anyway. But blogs are a nice medium to do so, and I think going forward we need to be more proactive in countering nutritional misinformation. I plan to do more of this here.

Recently, both Levinovitz and Perlmutter appeared on a radio show on the topic of gluten. It isn’t long- start at 15 minutes in and listen to about 35 minutes. Perlmutter drops a few references so we can see if they back up what he is claiming without spending days going through his books.

The episode is supposed to be about gluten, but Perlmutter pretty quickly steers the conversation to carbohydrate in general and the brain. Of note, at the start, he mentions Dr. Alessio Fasano to support his generalized connection between gluten and leaky gut, but Fasano has stated that Perlmutter’s book is “full of exaggeration and generalization“.

Reference 1.

28:30 minutes: “study of more than 27,000 individuals for 58 weeks in 40 countries and demonstrated the powerful role of the diet in determining a person’s risk in becoming demented”

This paper is here: “Healthy eating and reduced risk of cognitive decline: A cohort from 40 countries.”

This study used the “Alternative Healthy Eating Index” to assess diet quality and correlate it with cognitive decline in a population at high cardiovascular risk. It is notable that this index rates whole grains as a positive factor in the index. A higher score on this index, the lower association with cognitive impairment. This study says nothing about carbs or gluten specifically, although it would benefit Perlmutter to read the discussion, which notes a meta-analysis suggesting that adherence to a Mediterranean diet is associated with a reduced risk of cognitive impairment. This diet includes plenty of carbohydrates and gluten.

Reference 2.

29:30 minutes: “Dr. Dale Bredesen at UCLA has actually for the first time in history published results where he’s been able to reverse Alzheimer’s … but he did so by using a 36 point approach, not a pill … including exercising, repleting vitamin D, lowering carbohydrate, gluten free, welcoming fat back to the table, adjusting sleep patterns, the point is, we’re now starting to understand food matters… The study demonstrated that those individuals who ate less carbohydrates less of a refined diet has less chance of becoming demented.”

By the very design of this study we can’t know for sure if any of these dietary changes actually did matter. Here are the lifestyle changes for one participant:


This everything-but-the-kitchen-sink approach may be clinically interesting (although it can easily be argued that many of these treatments are not based on strong evidence or plausibility) but it certainly can’t lead us to say that any one change like reducing carbohydrates or gluten was a reason it was effective. For one, the improvements were almost all subjective/anecdotal- this was not a clinical study measuring some objective brain measure before and after treatment in a bunch of people and performing statistical analysis. It also noted that adherence was a problem, but didn’t measure how closely the patients adhered to each goal. We don’t know if they actually reduced carbohydrates or gluten. Not all of the patients were on the same program, either.

In other words, not a strong study to cite when suggesting to put the entire population on a low carbohydrate diet.

Reference 3.

30:10 minutes: “a study published in the Journal Alzheimer’s Disease [sic] from 2013 where Mayo Clinic researchers demonstrated over about a 6.5 year period of time that those individuals who at the most carbohydrate had an increased risk for dementia of 88%, whereas those individuals who derived most of their calories from fat had a 44% reduced risk for dementia”

This study used a food frequency questionnaire to assess the diets of 937 people in a county in Minnesota aged 70-89 years. Cognitive status was assessed by an examination and cognitive testing. Indeed, there was an association between high carbohydrate intake (>58%) and cognitive impairment, and a negative association with high fat. However, there was a trend between increased percentage of sugar and impairment that may suggest that carbohydrate/diet quality is the issue, which the authors note in the discussion. Such studies have weaknesses in what they can tell us, and the authors note that we can’t rule out reverse causation:

“The dietary patterns observed may be causal or alternately, may be a marker for preclinical disease and risk of cognitive impairment or dementia in elderly persons. These associations need to be examined in other longitudinal studies.”

It would be extremely premature to conclude that all carbohydrate is bad from such research, and there is again nothing here about gluten.


Anyone trained in science can easily see that these studies are weak support for a blanket case against carbohydrate and gluten and the brain (and parts of them directly contradict it). Perlmutter should be able to cite strong, well-designed clinical trials and longitudinal studies if there was convincing research.

He goes on to say (even though, again, the interview was supposed to be about gluten) that we need to eat fermented foods to nurture our microbiome to prevent dementia, discussing a list of indicators that you may have “trauma” in your microbiome, but I am not aware of any strong evidence to support these claims. The science of the microbiome is in its infancy, and it is inappropriate to invoke it to make definitive disease connections to an impressionable public. No doubt we have a lot to learn about the microbiome and health, and there are likely meaningful connections, but that doesn’t mean we can fill the gaps with the certitudes that Perlmutter does.

  • Andrea

    Very well done. Thank you for writing this.

  • Gunnar Fox

    I urge the author to eat plenty of heart-healthy whole grains (preferably U.S. wheat to ensure heavy gluten content) and to avoid fermented foods. I infer from the above that this is the prudent course until we have certitude about everything and until Dr. Perlmutter is deemed to be unassailable by the reigning medical establishment. He is an experienced clinician who deals with real people and creates positive outcomes but apparently that shouldn’t count for anything. The benefits people experience from following his pseudoscientific advice are actually placebo effects, including massive weight loss and improved cognitive function. So carry on and keep doing what you’re doing folks. Follow the same advice that has gotten you here, in all of its magnificent certitude. Eventually your obesity and Alzheimer’s will respond, I guess.You have too much to lose by trying something simple and inexpensive when a costly pharmaceutical is just around the corner. Wait for the magic pill!

    • http://www.nutsci.org Colby

      until we have certitude about everything and until Dr. Perlmutter is deemed to be unassailable by the reigning medical establishment.

      This assumes research will deem his advice good…which is a far stretch. We have never found anything that causes the range of diseases that he claims gluten/wheat does.

      The benefits people experience from following his pseudoscientific advice are actually placebo effects, including massive weight loss and improved cognitive function.

      There are people who claim the same from high grain, low fat diets. See the problem? This is why we need objective data before demonizing a large part of the global diet.

      You have too much to lose by trying something simple and inexpensive when a costly pharmaceutical is just around the corner. Wait for the magic pill!

      It is far from simple for the majority of people to avoid grains and gluten completely, and likely much more expensive. What do drugs have to do with wanting a high standard of evidence?

      • Gunnar Fox

        Interestingly, you didn’t deal with my first sentence. You are so confident you are doing God’s work by telling people to eat plenty of gluten I can only assume you are doing so yourself. I guess there’s no point in actually trying Paleo for 90 days? Nah… best to ignore the massive anecdotal tidal wave that avoiding grain has improved so many lives. What would happen if you actually try it and start to look, feel and perform better than ever by any objective measure? Oh dear! How would one explain that in the absence of proper evidence? Besides, it’s not effortless to put down the croissant, it’s far too complicated to swap heart-healthy whole grains for sweet potatoes… and not everyone could afford to stop eating grain so it’s just not practical. Let’s not disrupt that situation by creating a market for quality, nutrient-dense food. So many convenient excuses available for staying the same course that has led to epidemic ill health and obesity. See the problem?

        • http://www.nutsci.org Colby

          I didn’t deal with your first sentence because it is irrelevant to this post. I am not telling people what to eat. I simply looked at the references that Perlmutter provided, and showed that they do not support his narrative. The rest of your rant here also has nothing to do with this post.

          People are free to choose the diets they want to eat, but when an MD claims that research strongly supports his contentions, and it is easy to see that it doesn’t, that should give you pause.

          • Gunnar Fox

            Drs. Perlmutter and Gray experience success as clinicians. We may not yet fully understand the science behind the outcomes — but outcomes definitely matter.

            Again, I can only assume you have never tried eliminating grains. I would be curious as to why you (and others) deem this not to be a worthy experiment…

            Is it because you don’t respect the opinions of Paleo/Primal thought leaders who urge you to avoid wheat? Is it because you think gluten makes people better physically or cognitively? Are you a supporter of “high-grain, low-fat” diets you reference above based on scientific studies you find compelling? Do you dispute that feeding an animal wheat and corn is a great way to fatten it on a rapid timetable? Do you think gluten sensitivity tests are accurate and should be relied upon by people you care about? Or are you merely declining to avoid wheat in solidarity with people who do not have the means to avoid it?

            You may not deem my rant or this addendum to my rant relevant but at some point this is more than an intellectual exercise that we must confine to the bounds of a dry spreadsheet. I would actually be surprised, based on all we are learning, if you really think people are better off ignoring Dr. Perlmutter. But this seems to be the intended takeaway for folks.

            People who could make better choices take comfort in their suboptimal choices based on these pieces. Their lives are impacted. And we continue to have bad outcomes.

            So, again, what actionable advice are you proposing here in the wake of your purported takedown, after people are duly given pause by your analysis? Stay the course and keep eating grains? Or is this not relevant?

          • http://www.nutsci.org Colby

            You are reading way too far into this post. Again, I simply fact checked an interview.

            I would actually be surprised, based on all we are learning, if you really think people are better off ignoring Dr. Perlmutter.

            Of course they are. Read Dr. Levinovitz’s article that I linked to if you don’t see the problem from my post.

          • Gunnar Fox

            You are perceiving way less. I propose that you and “Dr. Leinovitz” go ahead and make an appointment to review your respective pieces in five years and see where we all stand.

  • http://www.mycfavisitcom.com/ Callie

    Great post! thanks

  • cat1tiddlywink

    I’m not a fan of Perlmutter, and I agree that *whole* grain consumption is associated with a lower risk of developing Alzheimers. However, as I read it, Bredesen’s protocol doesn’t call for a low-carb diet. He instead calls for reduction of *simple* carbohydrates, and in the paper mentions: eliminate white bread, white sugar, white flour items, white rice, white potatoes, I would assume added sugars, e.g. a low glycemic index diet. A low glycemic index diet can include plenty of legumes, vegetables, fruits, nuts, seeds, some animal protein (note I said some: increased saturated fat is not good for AD either), and perhaps some intact grains. (Intact as in “whole wheat berry” versus “ground up or processed”. ) This would be in line with studies I have seen over the last several years tying Alzheimer’s development to increased serum glucose. I am curious to know what Bredesen’s actual diet protocol is, though he mentions that participants were offered their choice of several variants of a low glycemic index diet. I myself am a fan of grains, but I will note that even the whole foods plant based diet proponents will discuss that even whole grain flours seem to have a higher glycemic index than intact grains (e.g. barley flour vs barley). Now of course there is the whole glycemic index vs glycemic load discussion, another ball of wax. At any rate, for someone facing down dementia, I think that it’s not unreasonable for them to consider cutting out anything made with flour for a few months along with some other lifestyle changes, such as more sleep and stress reduction. These things do not hurt and if they help, it is all to the good.