I've done a bit of research this morning on potatoes and got led to an old diabetic cookery book, published in 1916.
Since
@dunelm and
@PenguinMum were mentioning this earlier today, I've also included your names on here if that is okay.
I borrow online books from Archive.org
So looked on there. I found a book written by Rebecca Oppenheimer called Diabetic Cookery.
Here is the link. I hope it works.
https://archive.org/details/diabeticcookeryr00oppeiala
On page 135 she says "Peel potatoes, grate them, and let cold water run over them until all the starch has been washed out; this process takes some time.
This particular book I was able to download a pdf and put it in my Apple Books app so I can read it any time, but other more recent books you have to borrow as in a library.
>^..^<
Update: If anyone is interested, these are the other diabetic books that came up in search at Archive.org
https://archive.org/search.php?query=Diabetic Cookery
I am going to have a peek at them now....
Another update: I cannot access the site using my phone's sim card (it tells me no internet connection, but there is, it seems others have the same problem), but as long as I am on wi fi on iPhone, iPad, or on wifi on my Android tablet the Archive.org site opens up just fine.