Re: How they do it..

Here it is;
http://www.greenfacts.org/en/boron/boron-greenfacts-level2.pdf


Some highlights;

"Humans are primarily exposed to boron through food and drinking-water. The mean daily
intake of boron via the diet is about 1.2 mg per person per day"
The RDA is 3 mg...

It seems to be lower concentration in the soil of North America;

"Regions of the world Representative boron concentrations in surface water
Europe, Pakistan, Russia, and Turkey Mean concentrations below 0.6 mg/litre
Japan, South Africa, and South America Generally below 0.3 mg/litre
North America Typical concentrations below 0.1 mg/litre"

Sorry; my comment about sea water above is not correct;
"In marine invertebrate animals and fish, boron concentrations are similar to the boron
levels found in the oceans, i.e. between 0.5 and 4 mg/kg"
(my sticky brain remembered 4 and 5 = 4,5)

-but still quite an amount.. Probably a good therapeutic effect would be around this concentration.