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 (http://www.glutenfreesociety.org/gluten-free-society-blog/gluten-leaky-brain-the-connection-to-depression/), 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.

References

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