Dietary Boron: Possible Roles in Human and Animal Physiology

抄録

Boron is a bioactive element of low molecular weight. Since discovery of the first boron biomolecule, boromycin, in 1967, several other similar biomolecules are now well-characterized. Most recently described was a bacterial cell-to-cell communication signal that requires boron. Boron is a natural constituent of the diet and human consumption is not trivial: ∼1.00 mg/d for males aged 51 to 70 y. Boron may be under homeostatic control in humans and other mammals through regulatory mechanisms that remain undefined. Evidence for such control is enhanced by discovery of a specific mammalian borate transporter, NaBC1, expressed in the basolateral membranes of epithelial cells in tissues with excretory functions including kidney. Gastrointestinal absorption of boron approaches 100% but, even so, boron has a low order of toxicity. For adults, the Tolerable Upper Intake Level(UL)for boron is 20 mg/d, i.e ∼20-fold typical intakes. The Institute of Medicine has not set an Estimated Average Requirement(EAR),Recommended Dietary Allowance(RDA),or Adequate Intake(AI)for boron because the collective body of evidence has yet to establish a clear biological function for boron in humans. The evidence to date suggests that humans and higher animals(frog, zebrafish, chick, rat, and pig)may use boron to support normal biological functions. These findings suggest that boron has a role in bone structure and function, inflammation and immune processes, insulin metabolism, and completion of the life cycle. Development of animal models that lack boron transporters may help in identification of mechanisms of action responsible for the beneficial effects of dietary boron.