Ten women with severe osteoarthritis were given a six milligram boron supplement, and ten a placebo, for eight weeks. Five of the ten taking the boron supplement felt significant improvement, compared to only one of the ten taking the placebo. The 6 milligrams of boron were in two tablets containing 25mg of borax (sodium tetraborate decahydrate). There were no side effects noted. [1]
An earlier study,[2] had found that supplementing a low-boron diet with three grams of boron a day for 48 days increased beta-estradiol* and testosterone and reduced levels of calcium and magnesium in the urine of post-menopausal women. This suggested that the boron had reduced the rate at which bone was being eroded.
Another study confirmed that boron supplementation appeared to boost levels of sex hormones in both post-menopausal women (making it a possible natural and safer alternative to HRT) and in men of the same age.[3]

* the most powerful form of natural oestrogen