Controlled Intervention Studies in Humans

4 BORON AND STEROID HORMONES 4.4.1 Controlled Intervention Studies in Humans 

In a landmark study of the effect of boron on steroid hormone metabolism (Nielsen et al., 1987), postmenopausal women lived in a metabolic ward under controlled conditions for 167 days. For the first 119 days, the participants were fed basal diets, which provided 0.25 mg boron/day. The interventions also included dietary periods of magnesium and aluminum suppl entation. In two additional dietary periods, a subsample of the women was provided with a boron supplanent of 3 mg/ day. The study demonstrated, for the first time, that supplementation of postmenopausal women with a low dose (3 mg/day) of boron increases significantly the plasma concentrations of 17b-estradiol and testosterone. The study showed also that boron suppl entation decreases significantly the urinary excretion of calcium and magnesium. 

In a later study in women who were deprived of dietary magnesium, boron suppl entation resulted in a decrease in the serum 17b-estradiol concentration (Nielsen, 2004), and the plasma progesterone concentration was influenced by a boron x magnesium interaction. This study confirmed the existence of an interaction between boron and other nutrients, spedficaUy magnesium, under conditions of metabolic stress (Nielsen, 2008). 

The effect of boron on plasma steroid hormones was examined further in a metabolic study by Beattie and Peace (1993). Utilizing a study design that tested the effect of boron per se, the authors found no effect on plasma estradiol or testosterone concentrations in postmenopausal women. The authors suggest that the lack of concordance between their results and the findings of Nielsen et al. 

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