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“.
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.
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.
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.