Boron
A bioactive trace element for bone, mineral, and hormone metabolism — promising but unproven
Preliminary evidence
🧂Mineral
Evidence tier
Preliminary
Research weight
Citations
8 verified / 8
Classification
Mineral
❝
What the evidence says. Early or small human trials; promising but not yet conclusive.
What is Boron?
Boron is a mineral used for reduces urinary calcium and magnesium loss and raises serum estradiol/testosterone in boron-depleted postmenopausal women (usda metabolic-ward studies) — correcting low intake, not a benefit shown in replete people. NutriDex grades the human evidence as Preliminary. Boron is an ultratrace element that is not formally classified as essential for humans, and no clinical deficiency syndrome has been defined. Controlled metabolic-ward studies show it modulates calcium, magnesium, and vitamin D metabolism and raises serum estradiol and testosterone — but mainly in people first depleted of boron, and the doses studied (about 3 mg/day) are within the range of a normal fruit-and-vegetable diet. Supplementation trials in already-replete people are small, short, and inconsistent: a one-week study reported higher free testosterone in 8 men, while a 7-week trial in bodybuilders found no effect, and calcium-fructoborate pilots show short-term reductions in osteoarthritis pain and CRP. There is no RDA; the Tolerable Upper Intake Level is 20 mg/day, set primarily on animal reproductive/developmental toxicity.
Purported Benefits
✓Reduces urinary calcium and magnesium loss and raises serum estradiol/testosterone in boron-depleted postmenopausal women (USDA metabolic-ward studies) — correcting low intake, not a benefit shown in replete people
✓Calcium-fructoborate pilots show short-term reduction in knee osteoarthritis pain (WOMAC down ~29% at 14 days) and inflammatory CRP
✓May support bone-mineral metabolism via effects on vitamin D and steroid hormones; observational data link higher boron intake to better bone density
✓A single small short-term study raised free testosterone and lowered estradiol in healthy men, but this has not been replicated in longer trials
✓Adequate dietary intake (fruits, vegetables, nuts, legumes) plausibly contributes to bone and joint health, though causality is unproven
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
| Outcome | Evidence | Effect | Studies |
|---|---|---|---|
| Reduces urinary calcium/magnesium loss in boron-depleted womenMetabolic-ward studies show mineral retention, but only after deliberate depletion — correcting low intake, not benefit in replete people. | Preliminary | ↑ benefit · moderate | 2 |
| Raises serum estradiol/testosteroneHormone shifts seen in depleted women and one tiny short male study, but unreplicated in longer trials. | Preliminary | ↔ mixed · small | 2 |
| Reduces knee osteoarthritis pain (calcium fructoborate)Two small short-term DB pilots show ~29% WOMAC drop at 14 days; tests the fructoborate complex, not boron alone. | Preliminary | ↑ benefit · moderate | 2 |
| Lowers inflammatory CRPSingle calcium-fructoborate pilot in OA patients showed reduced CRP; biomarker only, short-term. | Preliminary | ↑ benefit · small | 1 |
| Improves bone-mineral metabolism / densityPlausible via vitamin D/steroid effects and observational links, but causality unproven and no RDA established. | Preliminary | ↔ mixed | 2 |
Dosing & Compounds
Typical Dose
No RDA, AI, or EAR established (data judged insufficient by the US Food and Nutrition Board). Typical dietary intake is roughly 1-1.5 mg/day; common supplements provide 3-6 mg/day. WHO considers ~1-13 mg/day an acceptable safe range. Tolerable Upper Intake Level (UL) for adults: 20 mg/day (elemental boron); 17 mg/day for ages 14-18, lower for children.
Active Compounds
Safety & Cautions
UL is 20 mg/day for adults. The UL is driven by reproductive and developmental toxicity (testicular atrophy, reduced fertility, fetal effects) seen in animal studies (rat fertility NOAEL ~17.5 mg/kg/day; developmental NOAEL ~9.6 mg/kg/day); these effects have NOT been observed in highly exposed boron workers in China and Turkey, whose blood levels stay below animal NOAELs. Acute boric-acid/borax poisoning (large overdoses) causes nausea, vomiting, diarrhea, dermatitis, and at extreme doses CNS and renal toxicity. Boron is renally excreted, so impaired kidney function raises accumulation risk. Because boron raises estradiol/testosterone, caution is reasonable in hormone-sensitive conditions; it may also raise serum estrogen with hormone therapy. Borax/boric acid powders are not safe to ingest. Supplemental doses (3-6 mg/day) are far below the UL and generally well tolerated short-term. Educational only — always check with your doctor or pharmacist before combining Boron with any medicine.
Key Studies
Agency / regulator
NIH Office of Dietary Supplements
✓ Source
Health Professional Fact Sheet states no RDA/AI is set for boron (data insufficient), typical intakes are modest, and the adult Tolerable Upper Intake Level is 20 mg/day based largely on animal reproductive/developmental toxicity.
RCT (pilot)
Scorei 2011 (Biol Trace Elem Res)
✓ Full text
Double-blind placebo-controlled pilot in middle-aged primary osteoarthritis patients found calcium fructoborate (boron source) reduced systemic inflammation markers including CRP (up to ~60% vs baseline) and improved dyslipidemia markers over short-term use.
RCT
Reid 2014 (Clin Interv Aging)
✓ Full text
Randomized double-blind placebo-controlled study (n=60) reported calcium fructoborate reduced WOMAC by ~29% and McGill pain by ~14% at day 14 in subjects with knee discomfort, with no adverse effects.
Safety / toxicology review
Khaliq/Bolt 2020 (Arch Toxicol)
✓ PubMed
Review of human reproductive data found that despite high occupational/environmental boron exposure in Chinese and Turkish workers, no boron-mediated reproductive effects were observed; human blood boron stayed >2-4x below animal NOAELs for fertility and developmental toxicity that underlie the UL.
Controlled human trial
Nielsen 1987 (FASEB J)
✓ PubMed
In 12 postmenopausal women on a low-boron diet, 3 mg/day boron supplementation markedly reduced urinary calcium and magnesium excretion and raised serum 17-beta-estradiol and testosterone, with effects more marked under low dietary magnesium.
Controlled human trial
Nielsen 1997 (Magnes Res)
✓ PubMed
Metabolic-ward study in postmenopausal women found low dietary boron elevated urinary calcium/magnesium loss and that supplemental boron (3 mg/day) altered mineral retention and blood mineral concentrations, supporting a metabolic role in mineral handling.
Review
Pizzorno 2015 (Integr Med)
✓ Full text
Narrative review concludes boron influences bone growth, calcium/magnesium and vitamin D metabolism, steroid hormones, and inflammation, and that the absence of harm studies supports considering 3 mg/day for diets low in fruits/vegetables — while acknowledging no RDA and limited high-quality human data.
Review
Nielsen 2014 (J Trace Elem Med Biol)
✓ PubMed
Authoritative update concludes boron is a bioactive element that beneficially affects bone, brain, and hormone/inflammation pathways in nutritional amounts, but human data remain insufficient to establish essentiality or a dietary requirement.