Should You Avoid Dairy if You Have Hashimoto’s Disease?

In the last several months, we’ve examined how certain supplements such as vitamin D, genistein, cordyceps and inositol impact Hashimoto’s thyroiditis. Today, we’re going to investigate how dairy—in the form of lactose—affects Hashimoto's disease. Specifically, I’m going to be addressing these two points:   1. How avoiding dairy helps Hashimoto’s disease 2. How dairy affects the absorption of thyroid medication Background Before launching into our discussion, let’s talk briefly about lactose intolerance and what happens in the body when one has a sensitivity to lactose, the naturally occurring sugar in dairy products. Lactose intolerance is a disorder of the small intestine that results from reduced lactase enzymatic activity that in optimal situations would break down lactose into the simpler sugars: glucose and galactose. The papers published by Montalto et al. (2006) and Lomer et al. (2007) examined this condition in great depth. Behind-the-scenes, what you find in lactose intolerance is that lactose cannot be readily digested by the body. Lactose begins to accumulate in the small intestine which then leads to bacterial overgrowth, gas formation and an altered intestinal environment which may cause damage or injury to the intestinal villi. As you may recall from high school biology class, villi are the tiny structures lining the intestinal wall that allow nutrients to be absorbed. What’s problematic for those with Hashimoto’s disease is that lactose intolerance, by impairing intestinal absorption, could disrupt the circulation of thyroid medication. This has serious implications so let’s go to the first study that examines how restricting dairy consumption could help Hashimoto’s disease. The first research article I reviewed was published in the journal Endocrine in 2014 and was entitled “Decrease in TSH levels after lactose restriction in Hashimoto’s thyroiditis patients with lactose intolerance.” The authors had noticed that existing research on the prevalence of lactose intolerance in patients with hypothyroidism was lacking. There were also no studies on the effect of restricting dairy/lactose consumption in Hashimoto’s patients who took thyroid medication (which we shall refer to as ‘LT4’ moving forward). The authors carried out this study for a twofold purpose: 1. to determine the frequency of lactose intolerance in patients with hypothyroidism and 2. to examine the effects of lactose restriction on thyroid function in Hashimoto’s patients with lactose intolerance. How was the study done? Eighty-three patients with Hashimoto’s...