There is an association between autoimmune diseases including chronic autoimmune thyroiditis (Hashimoto’s Disease) and Celiac Disease. Celiac disease, and even non-celiac gluten sensitivity, has become a topic of discussion amongst those debating health and wellness on the internet with some extreme views giving strong opinions that gluten (wheat protein) is causing destruction to everyone’s thyroid and thus thyroid function. As an endocrinology fellow with a background of nutrition interest and certification in obesity medicine, I thought I should at least look over the evidence and give a more reasonable evidence-based opinion to balance out the false sense of fear which is being spouted by some doctors, but mostly non-medical “practitioners.” While this is by no means a comprehensive or systematic review, the statistics are fairly constant and should be presented in such a manner.
The prevalence of actual celiac disease in the United States was evaluated in a large multicenter study a few years back using antibodies, genetic testing, and confirmatory intestinal biopsies and compared “at risk” (those with family history, gastrointestinal symptoms, or other autoimmune disorders) versus those not at risk with results showing just under 5% of “at risk patients” and just under 1% of other asymptomatic patients have celiac disease. Now this doesn’t take into account the so-called “non-celiac gluten sensitivity” folks which is a tangential topic off from this. For a deeper read on the whole topic of gluten, I recommend reading the June issue of Alan Aragon’s Research Review where Andrew Abbate addressed it nicely.
Now back to the thyroid. The “Clinical Practice Guidelines for Hypothyroidism in Adults” was co-sponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association was updated in 2012 are evidence based practice recommendations and discusses the strong association between autoimmune thyroid disease and other autoimmune disease amongst those with genetic susceptibility which has been common knowledge within medicine for a long time. They cite the National Health and Nutrition Examination Survey (NHANES III) for prevalence of hypothyroidism in the United States to be 0.3% overtly and 4.3% subclinically hypothyroid while thyroglobulin and thyroid peroxidase antibodies are present in about 10-11% of the “healthy population” which does predict progression to thyroid disease. Other studies cited have marginally different rates of published prevalence.
So what about the question, “does gluten really destroy your thyroid?” There is evidence for the tissue-transglutaminase antibodies in celiac patients perhaps directly contributing to development of thyroid disease by binding transglutaminase in follicular thyroid cells while also correlating to thyroid-peroxidase antibodies (predominant antibody in Hashimoto’s Disease) but this was not the case for “normal controls in that study.” Multiple prospective studies have looked at this from both angles.
i. One with 90 pediatric celiac disease patients revealed that 14% of those celiac patients also had thyroid-related antibodies and that those antibodies disappeared on a gluten-free diet. For its worth, 11% of those patients also had autoimmune type 1 diabetes mellitus.
ii. Those findings were similar to a previous studied cohort of celiac patients of whom 14% also had thyroid disease (10% hypothyroid & 4% hyper) while 11% had thyroglobulin antibodies and 15% had thyroid peroxidase antibodies.
iii. A larger prospective multicenter study compared 241 untreated celiac disease patients against 212 normal controls and the prevalence of thyroid disease was in fact three times higher in the celiac group (31 cases vs 9). Interestingly, many of those cases were non-autoimmune mediated. The prevalence of euthyroid (no thyroid dysfunction yet) autoimmune thyroid disease was understandably higher also (14% vs 4%) and some patients did significantly improve upon one year of gluten-free diet.
iv. A prospective study of 83 patients with autoimmune thyroid disease evaluated for celiac disease showed that 4 (5%) did have evidence for celiac even though one of them was completely asymptomatic.
v. Another similar study of 100 patients with thyroid disease revealed a prevalence of celiac disease to be 2% and contrary to some other studies mentioned above, the thyroid antibodies did not disappear with a gluten-free diet.
So what does all this mean? Are the extremists correct telling everyone that gluten is destroying their thyroids? Well, the simple answer is absolutely not. For the vast majority of people, gluten itself is not harming thyroid tissue either directly or indirectly through antibodies. For the small portion of the population who has genetic susceptibility, there is an association between autoimmunity to gluten and thyroid tissue albeit statistically still in the minority of even those specific populations. Will eating a gluten-free diet improve autoimmune thyroid disease? Perhaps, for a small subset of that population, and certainly is not harmful in trying. I actually discuss this with all of my patients who develop autoimmune thyroid disease. It certainly is reasonable to discuss gluten sensitivity and perhaps even evaluate for it further. I also discuss the consideration for a gluten-free diet with the statistics mentioned above as evidence that it could improve their disease, albeit unlikely. As long as going gluten-free leads patients to eating more vegetables, legumes, fruits, and other non-gluten whole grains as their sources of carbohydrate, I am very supportive. My only concern is for those who go gluten-free and then eat all the marketed processed boxed-goods found at every store these days. So if you want to go gluten-free as part of your thyroid treatment or prevention program, by all means try it out. But don’t be scare mongered into thinking gluten will destroy everyone’s thyroid.