Boron
Human boron research is a handful of small trials. In 19 bodybuilders, 2.5 mg a day did not change testosterone, lean mass or strength. In 8 men, free testosterone rose from baseline after a week of 10 mg a day. Findings in postmenopausal women disagree. A man who took a 1,000-fold dose of borax needed dialysis.
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- Status
- Dietary supplement in the US.
- Also called
- boron citrate, boron glycinate, calcium fructoborate, boric acid, borax, sodium tetraborate
- Taken for
- testosterone, free testosterone, estrogen, muscle, strength, bone health, joint pain, arthritis, menstrual pain, kidney stones
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help2
Reported risks2
What people take it for, and what was found
Shown to help2
Menstrual pain
One trial found 10 mg a day lowered menstrual pain severity and duration over two cycles in 113 female students.
Joint pain and arthritis
Small trials found boron supplements eased knee discomfort over 2 weeks and lowered inflammation markers in arthritis. Several were short, and one was run by the maker.
The numbers and sources
- Effect
- In 60 adults with self-reported knee discomfort, calcium fructoborate 110 mg twice a day lowered McGill Pain Questionnaire scores by 8.9 points and WOMAC scores by 13.73 points more than placebo at day 14 (both p < 0.0001), with no change on placebo [10]. In 60 adults with knee osteoarthritis, 15 days of calcium fructoborate improved C-reactive protein, fibrinogen and sedimentation rate against placebo, with no serious adverse events [11]. In 72 people with rheumatoid arthritis on etanercept, calcium fructoborate or borax (6 mg of boron a day) for 60 days improved disease activity scores and lowered ESR, hsCRP, IL-1α, IL-6 and TNF-α against placebo [12]. A 1994 review reported a 20-person trial in osteoarthritis in which 50% improved on 6 mg of boron a day against 10% on placebo [13].
- Population
- 60 adults aged 35 to 65 with knee discomfort in Mexico [10]. 60 middle-aged adults with knee osteoarthritis [11]. 72 adults with rheumatoid arthritis in Iraq [12]. 20 adults with osteoarthritis [13].
- Sources
- [10], [11], [12], [13]
- Caveats
- Trials ran 2 weeks to 2 months. The knee discomfort trial was designed by FutureCeuticals, which supplied the calcium fructoborate and employed most authors [10]. The 20-person trial is known only from its author's review [13]. No meta-analysis was located.
Mixed results2
Testosterone
Small trials found opposite results: 2.5 mg a day did not change testosterone in bodybuilders, while 10 mg a day for a week raised free testosterone in 8 men.
The numbers and sources
- Effect
- Sources disagree. Over 7 weeks, 2.5 mg a day did not change total or free testosterone against placebo. Testosterone rose in both groups with training [1]. After one week of 10 mg a day, mean free testosterone rose, estradiol fell, and dihydrotestosterone rose [2].
- Population
- 19 male bodybuilders aged 20 to 27 [1]; 8 healthy men [2].
- Sources
- [1], [2]
- Caveats
- Both studies are small. In [2], placebo was given on one day only, the one-week result compares each man with his own baseline, and the abstract gives no effect sizes.
Bone and calcium balance in women
Small trials found opposite results: one found 3 mg a day lowered urinary calcium in postmenopausal women, while another found no effect. No fracture outcomes were studied.
The numbers and sources
- Effect
- Sources disagree. Adding 3 mg a day to a low-boron diet lowered urinary calcium and magnesium and raised serum estradiol and testosterone [3]. A later study using 3 mg a day after a low-boron diet found no effect on minerals, sex steroids or markers of bone breakdown [4]. Over one year in female college students, boron changed serum phosphorus and magnesium. The abstract reports bone density by activity group, not by supplement [5].
- Population
- 12 postmenopausal women aged 48 to 82 in a metabolic unit [3]; healthy postmenopausal women in a metabolic unit [4]; 17 athletes and 11 sedentary women [5].
- Sources
- [3], [4], [5]
- Caveats
- Tiny studies, mostly measuring blood and urine markers over weeks. No fracture outcomes.
Not shown to help2
Muscle and strength
One small trial found 2.5 mg a day did not change lean mass or strength gains over 7 weeks in 19 male bodybuilders.
Kidney stones
One small trial found 10 mg a day did not reduce kidney stone number or size over 8 weeks in 60 patients.
The numbers and sources
Doses studied
Trials used 2.5 mg a day [1], 3 mg a day [3][4] and 10 mg a day [2][6][7]. The authors of a 2026 poisoning case cite the German Federal Institute for Risk Assessment as advising a maximum daily dose of 0.5 mg [8]. EFSA sets a tolerable upper intake level of 10 mg a day for adults, including during pregnancy and lactation [9].
Risks
Reported risks2
Poisoning from borax taken as a supplement
Case reports: a man who took about 1,000 times the intended borax dose had vomiting, diarrhea and skin redness, and recovered after hemodialysis.
The numbers and sources
- Effect
- A 66-year-old man took about 50 g of borax (disodium tetraborate decahydrate) for osteoarthritis, using a household spoon in place of the package's measuring spoon, about 1,000 times the intended dose. He developed diarrhea, vomiting, low urine output and widespread skin redness. Blood boron was 35.1 mg/L before hemodialysis and 1.09 mg/L after. He went home after 3 days [8].
- Population
- One case [8].
- Sources
- [8]
- Caveats
- A single case report of a dosing error.
Changes in sex hormones
Small trials found 10 mg a day lowered estradiol in men, while 3 mg a day gave opposite results in two studies of postmenopausal women.
The numbers and sources
- Effect
- In men, estradiol fell and dihydrotestosterone rose after one week of 10 mg a day [2]. In postmenopausal women, 3 mg a day raised serum estradiol and testosterone in one study [3] and did not change them in another [4].
- Population
- 8 men [2]; postmenopausal women in metabolic units [3][4].
- Sources
- [2], [3], [4]
- Caveats
- Hormone shifts were measured, and no study followed health outcomes.
Claims tested and not found
- That boron raises testosterone in men who train. In 19 bodybuilders over 7 weeks, testosterone did not differ from placebo [1].
- That boron builds muscle or strength. Lean mass and 1RM lifts did not differ from placebo [1].
- That boron clears kidney stones. Stone number and size did not differ from placebo over 8 weeks [7].
Sources
- Ferrando AA, Green NR. The Effect of Boron Supplementation on Lean Body Mass, Plasma Testosterone Levels, and Strength in Male Bodybuilders. International Journal of Sport Nutrition. 1993. https://doi.org/10.1123/ijsn.3.2.140
- Naghii MR, Mofid M, Asgari AR, et al. Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines. Journal of Trace Elements in Medicine and Biology. 2011. https://doi.org/10.1016/j.jtemb.2010.10.001
- Nielsen FH, Hunt CD, Mullen LM, et al. Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women. The FASEB Journal. 1987. https://doi.org/10.1096/fasebj.1.5.3678698
- Beattie JH, Peace HS. The influence of a low-boron diet and boron supplementation on bone, major mineral and sex steroid metabolism in postmenopausal women. British Journal of Nutrition. 1993. https://doi.org/10.1079/bjn19930087
- Meacham SL, Taper LJ, Volpe SL. Effects of boron supplementation on bone mineral density and dietary, blood, and urinary calcium, phosphorus, magnesium, and boron in female athletes. Environmental Health Perspectives. 1994. https://doi.org/10.1289/ehp.94102s779
- Nikkhah S, Dolatian M, Naghii MR, et al. Effects of boron supplementation on the severity and duration of pain in primary dysmenorrhea. Complementary Therapies in Clinical Practice. 2015. https://doi.org/10.1016/j.ctcp.2015.03.005
- Vousoughi G, Soleimanzadeh H, Radkhah N, et al. The Effect of Boron Supplementation on Kidney Stones in Patients With Nephrolithiasis: A Double-Blind Randomized Controlled Trial. Food Science & Nutrition. 2025. https://doi.org/10.1002/fsn3.70777
- Voß M, Brandhorst G, Scheer D. Accidental boron poisoning from a dietary supplement. Deutsches Ärzteblatt International. 2026. https://doi.org/10.3238/arztebl.m2026.0043
- European Food Safety Authority. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Version 11. 2025. https://www.efsa.europa.eu/sites/default/files/assets/UL_Summary_tables.pdf
- Reyes-Izquierdo T, Argumedo R, Phelan M, et al. Short-term efficacy of calcium fructoborate on subjects with knee discomfort: a comparative, double-blind, placebo-controlled clinical study. Clinical Interventions in Aging. 2014. https://doi.org/10.2147/cia.s64590
- Scorei R, Mitrut P, Petrisor I, Scorei I. A double-blind, placebo-controlled pilot study to evaluate the effect of calcium fructoborate on systemic inflammation and dyslipidemia markers for middle-aged people with primary osteoarthritis. Biological Trace Element Research. 2011. https://doi.org/10.1007/s12011-011-9083-0
- Hussain SA, Abood SJ, Gorial FI. The adjuvant use of calcium fructoborate and borax with etanercept in patients with rheumatoid arthritis: pilot study. Journal of Intercultural Ethnopharmacology. 2017. https://doi.org/10.5455/jice.20161204021549
- Newnham RE. Essentiality of boron for healthy bones and joints. Environmental Health Perspectives. 1994. https://doi.org/10.1289/ehp.94102s783