Is There Really a Food Grade Borax?

I have been adding 1/8 tablespoon Borax per liter to all of my drinking water for over a year now. It's the regular Borax sold in the Markets as a detergent. I have had no problems whatsoever and only benefits to the reduced amount of pain in my severely arthritic knee. I just received a comment on a post on Instagram claiming that I need to use "food grade Borax." Knowing that there's a prolific amount of BOTS(Big Harma) spreading a prolific amount of disinformation in regards to things, such as Borax, that have a large and inexpensive, health benefit- I submit this inquiry as to whether there truly is a "food grade Borax" and whether or not I should bother switching to it??