Louise... in the book,
Encyclopedia of Nutritional Supplements (Michael T. Murray, ND), it says that "There is no RDA for boron. A daily intake of 1.5 milligrams to 3.0 mg is safe and probably more than adequate.
Under Dosage Range, it says... In order to guarantee adequate boron levels, supplementing the diet with a daily dose of 3 to 9 milligrams is indicated, especially in individuals at risk for osteoporosis.
Safety: Orally administered boron is extremely safe when taken at recommended levels of 3 to 9 mg a day. Problems such as nausea, vomiting and diarrhea occur only at extremely high doses >500 mg/day.
Interactions: There are no known interactions with boron and any nutrient or drug."
Jackie