Gluten mad!

Tonight as I was browsing Facebook again, I came across an article a person had posted on gluten. The article claimed that gluten is connected to depression, and indeed, nearly every other neurological disorder for good measure.

Gluten is a protein found in certain grains like wheat, barley and rye. Gluten also makes foods taste better and improves their texture, so it’s often added to everything else.

The “gluten is toxic” meme is a very catchy one that’s doing the rounds again. I first heard of the idea that gluten is the cause of nearly every disease when I was in medical school, when every person I knew who’d seen a naturopath was told they had gluten intolerance and were conned into an unappetising and restrictive diet which didn’t make any of them better.

The same meme is now making it’s way back around again now that the low-fat, sugar-free, zucchini broth-type diet fads are waning.

The proposed link between depression, anxiety and gluten is a new twist to the old story. But with depression becoming a preeminent disease in the 21st century, the link doesn’t surprise me.

So what does the evidence say? Is gluten the culprit behind the modern scourge of mental illness?

I certainly don’t think so, at least according to my interpretation of the medical literature. As far back as 2001, researchers studying the mental health of patients with coeliac disease noted that coeliac disease patients had much higher levels of anxiety and depression than healthy matched controls (up to about three to six times greater in one study), and after a year on a gluten free diet, there were no changes to the rates of anxiety and depression (Addolorato et al., 2001).

In more recent times, larger studies have been performed. Hauser, Janke, Klump, Gregor, and Hinz (2010) confirmed higher levels of anxiety in German female coeliac patients who were on a gluten free diet, compared to the normal controlled population. Mazzone et al. (2011) showed that children with coeliac disease on gluten-free diets for about 7 years on average still showed an increased rate of anxiety and depression symptoms and showed higher scores in “harm avoidance” and “somatic complaints” as compared to healthy control subjects.

A larger cross sectional survey was performed in the Netherlands in 2013, on 2265 adults with coeliac disease (van Hees, Van der Does, & Giltay, 2013). That survey showed that a significantly higher proportion of those with coeliac disease, despite being on a strict gluten free diet, reporting a higher rate of anxiety and depression compared to the general population. It also showed (albeit in a smaller subgroup of respondents) that poor adherence with a gluten free diet did not affect the likelihood of depressive symptoms.

To be fair, cross sectional surveys and longitudinal cohorts aren’t necessarily the strongest form of evidence, but it is the best we’ve currently got. There was a recent randomised controlled trial, a stronger form of evidence, looking at the effect the introduction of gluten had on depressive symptoms in people who did not have coeliac disease but reported gluten sensitivity and were controlled on a gluten free diet (Peters, Biesiekierski, Yelland, Muir, & Gibson, 2014). While this showed some worsening of depressive symptoms in those subjects given gluten, the exposure was short, the effect was moderate, and the results should be considered cautiously given the small number of subjects reduced the power of the study.

Given the weight of evidence, I can’t help but be sceptical of books touting the ‘gluten = depression’ theory, books like “Grain Brain”. It’s author, American neurologist Dr David Perlmutter, attests that more than 38 different diseases are caused by gluten, including autism and depression. If you believe the celebrity chiropractor who reviewed Perlmutter’s work (, increased intestinal permeability and intestinal dysbiosis (“leaky gut” and bad gut bacteria) combine to increase inflammation in the blood and in the brain, causing depression.

But correlation does not equal causation. Just because brain diseases, inflammation and gut problems tend to occur together does not prove that gut problems cause inflammation and brain problems. Rather, the evidence suggests that it’s the other way around, with all of the processes linked to genetics.

For example, autism is related to a number of genes that both reduce the proteins that help nerve cells grow branches (Won, Mah, & Kim, 2013), and at the same time, switch on a low grade form of inflammation (Onore, Careaga, & Ashwood, 2012). I believe it’s the pre-existing inflammation that adds to the cellular dysfunction of the brain and at the same time, promoting low grade inflammation of a number of organs, including the gut. It’s the pre-existing inflammation that causes the gut to become “leaky”, not the “leaky” gut causing the inflammation.

Because if gluten was the primary cause, then why do people with coeliac disease who do not eat gluten report more depressive and anxious symptoms than control groups who do eat gluten? Why would those with coeliac disease who are eating sporadic gluten be just as depressed as those patients who do not?

If you don’t have coeliac disease, then gluten free diets are just like Amway products. You really don’t need them, and you could probably do much better without them. All you’re really doing is just making someone else obscenely rich.

Not only are you wasting your money, but you might also be harming your health by eating gluten free foods, since most foods that are stripped of gluten are also stripped of most of their other nutrients.

As Nash and Slutzky (2014) summarise, “Every major change in our diet carries with it the possibility of unforeseen risks. Many readers — the general public, as well as medical professionals — accept what they read at first glance. Myths have been part of our medical lore for millennia. Those jumping on the gluten-free/high-fat bandwagon may be disappointed when their symptoms are not mitigated; more critically, they may be at increased risk for other, more dangerous ailments.”

If you really think you feel better off gluten, then talk to your doctor or registered dietician to make sure you remain healthy off it.


Addolorato, G., Capristo, E., Ghittoni, G., Valeri, C., Masciana, R., Ancona, C., & Gasbarrini, G. (2001). Anxiety but not depression decreases in coeliac patients after one-year gluten-free diet: a longitudinal study. Scand J Gastroenterol, 36(5), 502-506.

Hauser, W., Janke, K. H., Klump, B., Gregor, M., & Hinz, A. (2010). Anxiety and depression in adult patients with celiac disease on a gluten-free diet. World J Gastroenterol, 16(22), 2780-2787.

Mazzone, L., Reale, L., Spina, M., Guarnera, M., Lionetti, E., Martorana, S., & Mazzone, D. (2011). Compliant gluten-free children with celiac disease: an evaluation of psychological distress. BMC Pediatr, 11, 46. doi: 10.1186/1471-2431-11-46

Nash, D. T., & Slutzky, A. R. (2014). Gluten sensitivity: new epidemic or new myth? Every major change in our diet carries with it the possibility of unforeseen risks. Am J Cardiol, 114(10), 1621-1622. doi: 10.1016/j.amjcard.2014.08.024

Onore, C., Careaga, M., & Ashwood, P. (2012). The role of immune dysfunction in the pathophysiology of autism. Brain Behav Immun, 26(3), 383-392. doi: 10.1016/j.bbi.2011.08.007

Peters, S. L., Biesiekierski, J. R., Yelland, G. W., Muir, J. G., & Gibson, P. R. (2014). Randomised clinical trial: gluten may cause depression in subjects with non-coeliac gluten sensitivity – an exploratory clinical study. Aliment Pharmacol Ther, 39(10), 1104-1112. doi: 10.1111/apt.12730

van Hees, N. J., Van der Does, W., & Giltay, E. J. (2013). Coeliac disease, diet adherence and depressive symptoms. J Psychosom Res, 74(2), 155-160. doi: 10.1016/j.jpsychores.2012.11.007

Won, H., Mah, W., & Kim, E. (2013). Autism spectrum disorder causes, mechanisms, and treatments: focus on neuronal synapses. Front Mol Neurosci, 6, 19. doi: 10.3389/fnmol.2013.00019


Dr Caroline Leaf and the myth of the myth of multitasking

Screen Shot 2014-10-06 at 3.06.29 pm

Can you successfully multitask?

According to Dr Caroline Leaf, communication pathologist and self-titled cognitive neuroscientist, multi-tasking is a myth.

Actually, Dr Leaf isn’t completely wrong. Her factoid is so vague that there may be some truth in it somewhere. The problem with teaching via vague factoid is that no one can apply anything from it. If we were to take Dr Leaf’s statement as a specific teaching or advice, then we would be misled.

Why? Because it all comes down to how you define ‘multi-tasking’.

I have a couple of patients in a nursing home, two old ladies who sit on a balcony in the sun, knitting and talking at the same time. Isn’t that multi-tasking? Think of what you do every day. How often are you doing something menial while doing something requiring a bit more attention? How often do you have a conversation with your passenger while your driving? Isn’t that multi-tasking? When you get up in the morning and you are able to make a cup of tea and some breakfast at the same time, read some of the paper or your e-mails while you’re eating your breakfast at the same time, etc. Isn’t that multi-tasking?

We multi-task all the time. If we had to do everything in a linear, sequential fashion, we would never get anything done. We are able to multi-task because routine tasks have become largely habitualised by our brains and don’t need lots of processing power to complete. Hence why we can do something as complex a driving a car while still talking to our passenger or listening to music. Certain occupations, such as air-traffic control, involve high levels of multi-tasking [1].

When a task is new and/or complicated, our brains need to utilise our resources of attention to properly process the information required by the task. There is only so much that our working memory can handle. Our working memory uses tricks to handle larger amounts of information through a process called “chunking” [2] but there is still a finite limit. Performing two or more cognitively demanding tasks at the same time is difficult, and the brain can often cope by shifting tasks, although there is always a price to pay for this [3].

So it is true that there are some tasks that require more of the cognitive capacity of the brain to process. The higher the cognitive load, the more capacity needed, and the less likely that the brain will be able to multi-task with it. Thus, it’s reasonable to suggest that we can’t multi-task all of the time with every task we have to perform (although the more we do a task, the more habitual it becomes, thus reducing the cognitive load of the task, and increasing our ability to multi-task it).

However it’s misleading to say that we can’t multi-task at all. It’s a myth that multi-tasking is a myth. Dr Leaf’s comment that, “Paying attention to one task at a time is the correct way”, isn’t a summary of the neuroscience of attention, but a subjective statement based on her grandiose pretension. There is no objective evidence that “one task at a time” offers generally applicable benefit.

So don’t be afraid of multi-tasking. Just know your limits.


  1. Nelson, J.T., et al., Enhancing vigilance in operators with prefrontal cortex transcranial direct current stimulation (tDCS). Neuroimage, 2014. 85 Pt 3: 909-17 doi: 10.1016/j.neuroimage.2012.11.061
  2. Bor, D. and Seth, A.K., Consciousness and the prefrontal parietal network: insights from attention, working memory, and chunking. Front Psychol, 2012. 3: 63 doi: 10.3389/fpsyg.2012.00063
  3. Monsell, S., Task switching. Trends in cognitive sciences, 2003. 7(3): 134-40

Dr Caroline Leaf and the 98 Percent Myth

Dr Caroline Leaf believes that nearly all our diseases come from our thoughts.

Dr Caroline Leaf believes that nearly all our diseases come from our thoughts.

In the hustle and bustle of daily life, most people wouldn’t stop to consider what makes people sick.  In my profession, I get a front row seat.

In the average week, I get to see a number of different things.  Mostly “coughs, colds and sore holes” as the saying goes, although there are some rarer things too.  And sometimes, people present with problems that aren’t for the faint of heart (or stomach – beware of nail guns is all I can say).

Normally, the statistics of who comes in with what doesn’t make it beyond the desk of the academic or health bureaucrat.  The numbers aren’t as important as the people they represent.

But to Dr Caroline Leaf, Communication Pathologist and self-titled Cognitive Neuroscientist, the numbers are all important.  To support her theory of toxic thoughts, Dr Leaf has stated that “75 to 98% of mental and physical (and behavioural) illness comes from one’s thought life” [1: p37-38].  She has repeated that statement on her website, on Facebook, and at seminars.

As someone with a front row seat to the illnesses people have, I found such a statement perplexing.  In the average week, I don’t see anywhere near that number.  In general practices around Australia, the number of presentations for psychological illnesses is only about eight percent [2].

But Australian general practice is a small portion of medicine compared to the world’s total health burden.  Perhaps the global picture might be different?  The World Health Organization, the global authority on global health, published statistics in November 2013 on the global DALY statistics [3] (a DALY is a Disability Adjusted Life Year).  According to the WHO, all Mental and Behavioural Disorders accounted for only 7.2% of the global disease burden.

You don’t need a statistics degree to know that seven percent is a long way from seventy-five percent (and even further from 98%).

Perhaps a large portion of the other ninety-three percent of disease that was classified as physical disease was really caused by toxic thoughts?  Is that possible?  In short: No.

When considered in the global and historical context, the vast majority of illness is related to preventable diseases that are so rare in the modern western world because of generations of high quality public health and medical care.

In a recent peer-reviewed publication, Mara et al state, “At any given time close to half of the urban populations of Africa, Asia, and Latin America have a disease associated with poor sanitation, hygiene, and water.” [4] Bartram and Cairncross write that “While rarely discussed alongside the ‘big three’ attention-seekers of the international public health community—HIV/AIDS, tuberculosis, and malaria—one disease alone kills more young children each year than all three combined. It is diarrhoea, and the key to its control is hygiene, sanitation, and water.” [5] Hunter et al state that, “diarrhoeal disease is the second most common contributor to the disease burden in developing countries (as measured by disability-adjusted life years (DALYs)), and poor-quality drinking water is an important risk factor for diarrhoea.” [6]

Diarrhoeal disease in the developing world – the second most common contributor to disease in these countries, afflicting half of their population – has nothing to do with thought.  It’s related to the provision of toilets and clean running water.

We live in a society that prevents half of our illnesses because of internal plumbing.  Thoughts seem to significantly contribute to disease because most of our potential illness is prevented by our clean water and sewerage systems.  Remove those factors and thought would no longer appear to be so significant.

In the same manner, modern medicine has become so good at preventing diseases that thought may seem to be a major contributor, when in actual fact, most of the work in keeping us all alive has nothing to do with our own thought processes.  Like sanitation and clean water, the population wide practices of vaccination, and health screening such as pap smears, have also significantly reduced the impact of preventable disease.

Around the world, “Recent estimates of the global incidence of disease suggest that communicable diseases account for approximately 19% of global deaths” and that “2.5 million deaths of children annually (are) from vaccine-preventable diseases.” [7] Again, that’s a lot of deaths that are not related to thought life.

Since 1932, vaccinations in Australia have reduced the death rate from vaccine-preventable diseases by 99% [8].  Epidemiological evidence shows that when vaccine rates increase, sickness from communicable diseases decrease [9: Fig 2, p52 & Fig 8, p67].

Population based screening has also lead to a reduction in disease and death, especially in the case of population screening by pap smears for cervical cancer.  Canadian public health has some of the best historical figures on pap smear screening and cervical cancer. In Canada, as the population rate of pap smear screening increased, the death rate of women from cervical cancer decreased.  Overall, pap smear screening decreased the death rate from cervical cancer by 83%, from a peak of 13.5/100,000 in 1952 to only 2.2/100,000 in 2006, despite an increase in the population and at-risk behaviours for HPV infection (the major risk factor for cervical cancer) [10].

And around the world, the other major cause of preventable death is death in childbirth.  The risk of a woman dying in childbirth is a staggering one in six for countries like Afghanistan [11] which is the same as your odds playing Russian Roulette.  That’s compared to a maternal death rate of one in 30,000 in countries like Sweden.  The marked disparity is not related to the thought life of Afghani women in labour.  Countries that have a low maternal death rate all have professional midwifery care at birth.  Further improvements occur because of better access to hospital care, use of antibiotics, better surgical techniques, and universal access to the health system [11].  Again, unless one’s thought life directly changes the odds of a midwife appearing to help you deliver your baby, toxic thoughts are irrelevant as a cause of illness and death.

Unfortunately for Dr Leaf, her statement that “75 to 98 percent of mental, physical and behavioural illnesses come from toxic thoughts” is a myth, a gross exaggeration of the association of stress and illness.

In the global and historical context of human health, the majority of illness is caused by infectious disease, driven by a lack of infrastructure, public health programs and nursing and medical care.  To us in the wealthy, resource-rich western world, it may seem that our thought life has a significant effect on our health.  That’s only because we have midwives, hospitals, public health programs and internal plumbing, which stop the majority of death and disease before they have a chance to start.

Don’t worry about toxic thoughts.  Just be grateful for midwives and toilets.


1.         Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan:

2.         FMRC. Public BEACH data. 2010  [cited 16JUL13]; Available from: <

3.         World Health Organization, GLOBAL HEALTH ESTIMATES SUMMARY TABLES: DALYs by cause, age and sex, GHE_DALY_Global_2000_2011.xls, Editor 2013, World Health Organization,: Geneva, Switzerland.

4.         Mara, D., et al., Sanitation and health. PLoS Med, 2010. 7(11): e1000363 doi: 10.1371/journal.pmed.1000363

5.         Bartram, J. and Cairncross, S., Hygiene, sanitation, and water: forgotten foundations of health. PLoS Med, 2010. 7(11): e1000367 doi: 10.1371/journal.pmed.1000367

6.         Hunter, P.R., et al., Water supply and health. PLoS Med, 2010. 7(11): e1000361 doi: 10.1371/journal.pmed.1000361

7.         De Cock, K.M., et al., The new global health. Emerg Infect Dis, 2013. 19(8): 1192-7 doi: 10.3201/eid1908.130121

8.         Burgess, M., Immunisation: A public health success. NSW Public Health Bulletin, 2003. 14(1-2): 1-5

9.         Immunise Australia, Myths and Realities. Responding to arguments against vaccination, A guide for providers. 5th ed. 2013, Commonwealth of Australia, Department of Health and Ageing, Canberra:

10.       Dickinson, J.A., et al., Reduced cervical cancer incidence and mortality in Canada: national data from 1932 to 2006. BMC Public Health, 2012. 12: 992 doi: 10.1186/1471-2458-12-992

11.       Ronsmans, C., et al., Maternal mortality: who, when, where, and why. Lancet, 2006. 368(9542): 1189-200 doi: 10.1016/S0140-6736(06)69380-X