Does boron as a supplement do anything for your bones?

Boron is a trace mineral found in small amounts in nuts, fruit and vegetables. A deficiency of it appears to be unfavourable for bones: several reviews link low boron status to slower bone mass development in children and accelerated bone loss after menopause. That sounds promising, but it is a different thing from saying that extra boron above a normal intake adds anything on top.

What supplementation of 3 mg per day did do in postmenopausal women in one small experiment with 12 participants: the body excreted less calcium and magnesium through urine, and blood levels of estradiol (a female hormone that inhibits bone breakdown) and testosterone rose. Those are biologically plausible mechanisms for bone protection, but these were only 12 women and there was no measurement of bone density itself.

An observational study in 134 women found no association at all between daily dietary boron status and bone density of the spine or hip. Animal studies show mixed effects on bone strength, but how strong those effects are depends on the simultaneous intake of calcium, magnesium and vitamin D. Translation to humans is not possible on the basis of those studies.

Somewhat more can be said about safety: at extremely high doses (far above what is found in supplements) cell damage and reduced fertility occurred in animal experiments. A broad review study therefore emphasises that the amount must be right: too little does not help, too much is harmful. A guideline for osteoporosis mentions boron supplementation as a possible addition alongside calcium and vitamin D, but explicitly not as a standalone treatment.