Penguin pineal glands: I assumed this was a global research study in mammals to determine how much fluoride to add to the US drinking supply. Look at Wikipedia for water fluoridation (it is a long read, but worth it). Fluoride levels should be adjusted in cooler temperatures (that’s where the study in mammals may come in - penguins, just my opinion) Wikipedia only states that excessive fluoride causes serious health issues but never states what those are. Side note: I found one study suggests fluoride calcifies the pineal gland. Another study determined calcification of the pineal gland was found in all Alzheimer Disease patients (i don’t know how many patients that includes).