Description Boron is an ultratrace mineral.
Human requirements Boron is essential in plants and some animals, and evidence of essentiality is accumulating in humans; however requirements have not so far been deﬁned. The Food Standards Agency Expert Vitamins and Minerals (EVM) group set a safe upper level from supplements alone of 5.9mg daily.
Most UK diets appear to provide about 2mg daily.
Boron appears to be important in calcium metabolism, and can affect the composition, structure and strength of bone. It may also inﬂuence the metabolism of calcium, copper, magnesium, phosphorus, potassium and vitamin D. In addition, boron affects the activity of certain enzymes. It also affects brain function; boron deprivation appears to depress mental alertness.
Foods of plant origin, especially non-citrus fruits,leafy vegetables and nuts, are rich sources of boron, but there is little in meat, ﬁsh and poultry.Beer,wine and cider contain signiﬁcant amounts.
Dietary boron is rapidly absorbed. The mechanism of absorption from the gastrointestinal tract has not been elucidated.
Boron is distributed throughout the body tissues; the highest concentrations are found in the bone, teeth, ﬁngernails, spleen and thyroid.
Boron is excreted mainly in the urine.
No precise signs and symptoms of boron deﬁciency have been deﬁned.
Boron has been claimed to prevent osteoporosis and to both prevent and relieve the symptoms of osteoarthritis, as well as to improve memory.
In a study of 12 post-menopausal women, boron supplementation (3mg daily) reduced urinary excretions of calcium and magnesium, and elevated serum concentrations of estradiol and ionised calcium.
A further study has provided evidence that boron can both enhance and mimic some effects of oestrogen ingestion in post-menopausal women. In women receiving oestrogen therapy, an increase in boron intake increased serum oestradiol concentrations to higher levels than when boron intake was low. However, there is no evidence that boron supplements can relieve the symptoms of the menopause. The effects seen in this study did not occur in men or in women not receiving oestrogen therapy. However, another study in men found that supplementation with boron (10mg a day) signiﬁcantly increased oestradiol concentrations, and there was also a trend for plasma testosterone to increase. These ﬁndings support the contention that, if oestrogen is beneﬁcial to calcium metabolism, then boron might also be beneﬁcial.
However, another study in postmenopausal women showed that 3mg boron daily had no effect on bone mineral absorption and excretion, plasma sex steroid levels and urinary excretion of pyridinium crosslink markers of bone turnover. Moreover, in this study a low-boron diet appeared to induce hyperabsorption of calcium because positive calcium balances were found in combination with elevated urinary calcium excretion. The authors concluded that this phenomenon may have inhibited or obscured any effect of boron supplementation.
Boron has been claimed to relieve the symptoms of arthritis, but evidence is very weak. Epidemiological studies suggest that incidence of arthritis is higher in areas of the world where boron intake is low, and subjects with arthritis have been found to have lower bone boron concentrations. One double-blind controlled (but not randomised) trial in 20 patients with osteoarthritis found that boron (6mg daily) improved symptoms in ﬁve out of 10 subjects in the treated group, and one out of 10 subjects in the placebo group. However, statistical analysis wasn’t performed because the small number of subjects.
Three placebo-controlled, double-blind randomised trials in 28 healthy adults showed that low dietary boron (0.25mg/2000kcals) was associated with poorer performance of a variety of cognitive and psychomotor tasks and also depression of mental alertness than higher intake (3.25mg/2000kcals).
No problems have been reported.
Pregnancy and breast-feeding
No problems have been reported, but there have not been sufﬁcient studies to guarantee the safety of boron in pregnancy and breastfeeding. However, supplements are probably best avoided because of possible changes in oestrogen metabolism.
Boronisrelativelynon-toxic when administered orally at doses contained in food supplements. High oral doses (> 100mg daily) are associated with disturbances in appetite and digestion, nausea, vomiting, diarrhoea, dermatitis and lethargy. Toxicity has occurred, especially in children, from the application of boron-containing dustingpowdersandlotions(in the form of borax or boric acid) to areas of broken skin and mucous membranes. Such preparations are no longer recommended.
Riboﬂavin: large doses of boron may increase excretion of riboﬂavin.
Magnesium: boron supplementation may reduce urinary magnesium excretion and increase serum magnesium concentrations.
Boron is available in the form of tablets and capsules. The dose is not established. Dietary supplements provide, on average, 3mg per daily dose.
Upper safety levels
The UK Expert Group on Vitamins and Minerals (EVM) has identiﬁed a safe total intake of boron for adults from supplements alone of 5.9mg daily. The US Tolerable Upper Intake Level (UL) for boron, the highest total amount from diet and supplements unlikely to pose no risk for most people, is 20mg daily for adults; 17mg daily for youngsters aged 14–18;11 mg daily for youngsters aged 9–13; 6mg daily for children aged 4–8; and 3mg daily for children aged 1–3.
There is preliminary evidence that boron hasbeneﬁcialeffectsoncalciummetabolism in post-menopausal women by preventing calcium loss and bone demineralisation, but no evidence that it can prevent or be of beneﬁt in treating osteoarthritis. There is some evidence that diets low in boron impair cognitive function.
(extracted from) Dietary Supplements, Third Edition, by Pamela Mason, BSc, MSc, PhD, MRPharmS, published by Pharmaceutical Press, London, 2007.