Spinach is high in oxalates, and autopsy studies show oxalate deposition in the thyroid of all individuals.

“there's no physiologic reason for oxalate to be in the human thyroid that we know of and I think this is probably just an accumulation of oxalates in the thyroid because we consume them commonly in childhood leading to adulthood and they increase with age”

“interestingly they do note in this paper that people with Hashimoto's thyroiditis had less of the oxalate crystals possibly due to an autoimmune reaction clearing the thyroid crystals out perhaps there's some connection between oxalate crystals in the thyroid and Hashimoto's”

“There is no physiologic role for oxylic acid in the human thyroid. It's not supposed to be there. And yet, a 100% of people upon autopsy had deposition of oxalates in the thyroid.”

“The hypothesis being that there's maybe an immune reaction against the oxalate clearing it out or something.”

“And this is all to say that things like spinach, almonds, rhubarb, uh um beans, these are all very high sources of oxalates, we don't really fully understand what that is doing in the human body, especially at the level of the thyroid. There is no physiologic role for oxylic acid in the human thyroid. It's not supposed to be there. And yet, a 100% of people upon autopsy had deposition of oxalates in the thyroid. Maybe time to rethink the spinach salads.”

“Um spinach is very high in oxalates. And there are a couple of studies that looked at autopsy series and every single person in those autopsies had oxylic acid oxalate deposition in their thyroid. And the people with Hashimoto thyroiditis actually had lower levels of oxalate deposition.”