I looked at the first article and he stated that to get 6mg of Boron he took two tablets of PHARMA GRADE Borax (25-30mg) or almost 5x the required dosage.
To be practical; by that I mean that if I need 6-10mg of Boron daily I would need to take ~50mg of Borax. Also that Borax should be pharma grade since your washing powder can contain various other chemicals depending on grade.
Would I recommend eating ~50mg of Borax a day out of a washing powder box, NO.
Is it toxic, certainly no more than table salt :)