Supplements

Boron

Updated · 20 sources · Editorial policy

Boron is a trace element found mainly in fruit, legumes, nuts and drinks such as coffee and wine. It is essential for plants, but it is not classified as an essential nutrient for humans, because no clear biological function has been identified (NIH ODS). It is sold as a dietary supplement, usually in amounts of 0.15–6 mg of elemental boron.

In fitness circles boron is marketed as a “testosterone booster.” The evidence for that is thin. The only placebo-controlled trial in men who lift weights, 2.5 mg/day for 7 weeks in 19 bodybuilders, found no effect on testosterone, lean mass or strength (Ferrando and Green, Int J Sport Nutr 1993). The often-quoted rise in free testosterone comes from a one-week study of 8 men with no control group.

This page summarizes what the NIH Office of Dietary Supplements, the human studies and toxicology reviews report. It is for education only and is not medical advice.

Property Detail
Type Trace element; dietary supplement
Essential nutrient status Not established; no RDA, AI or Daily Value
Usual dietary intake (US adults) Median ≈ 0.9–1.4 mg/day
Common supplement amounts 0.15–6 mg elemental boron
Doses in human trials 2.5–12 mg/day; most often 3, 6 or 10 mg/day
Absorption About 85–90% of ingested boron
Half-life ≈ 21 h after an IV dose of boric acid in healthy men
Upper limit (US, adults 19+) 20 mg/day (Tolerable Upper Intake Level)
WADA status Not on the 2026 Prohibited List

What it is

In food it occurs as inorganic borates and as sugar-borate esters such as calcium fructoborate. Most ingested boron is converted to boric acid in the gut, and boric acid is the main form found in blood and urine (NIH ODS).

Supplements use many forms, for example sodium borate, boron citrate, boron glycinate and calcium fructoborate. The label states the amount of elemental boron, not the weight of the whole compound. No data compare how well the different supplement forms are absorbed.

How boron acts in the body is not known. One proposal is that boron binds molecules carrying neighboring hydroxyl groups (forming “boroesters”), such as S-adenosylmethionine and NAD, and so changes their activity (Nielsen, J Trace Elem Med Biol 2014). This remains a hypothesis.

Dietary sources

Plant foods supply most dietary boron. Selected values from the NIH fact sheet:

Food Boron per serving
Prune juice, 1 cup 1.43 mg
Avocado, ½ cup 1.07 mg
Raisins, 1.5 oz 0.95 mg
Peach, 1 medium 0.80 mg
Apple, 1 medium 0.66 mg
Peanut butter, 2 tbsp 0.46 mg
Coffee, 1 cup 0.07 mg
Milk, whole, 1 cup 0.04 mg

In the US, the main sources are coffee, milk, apples, beans and potatoes, mostly because people eat a lot of them. Median dietary intakes in US adults are 0.87–1.35 mg/day.

How it works in the body

Boron is well absorbed and does not build up in most tissues. Bone, nails and hair hold more boron than other tissues. Blood levels change little even when intake rises sharply, which suggests the kidneys raise excretion to keep levels stable (NIH ODS).

Parameter Value Source
Oral absorption ≈ 85–90% NIH ODS
Urinary recovery of a 10 mg/day supplement 84% (4 weeks, 18 men) Naghii and Samman 1997
Urinary recovery of an IV dose 98.7% within 120 h Jansen et al. 1984
Elimination half-life, IV boric acid 21.0 ± 4.9 h (healthy young men) Jansen et al. 1984
Half-life after accidental ingestion Mean 13.4 h (range 4.0–27.8 h; 9 patients) Litovitz et al. 1988
Fasting plasma boron, postmenopausal women 34–95 ng/mL NIH ODS

The kidneys clear almost all of it, and small amounts leave in feces, sweat, breath and bile. Boron status is not measured in routine clinical practice.

Regulatory status

  • Nutrient status. The US Food and Nutrition Board found the data too limited to set an RDA, Adequate Intake or Estimated Average Requirement for boron, so there is no Daily Value. The World Health Organization gives 1–13 mg/day as an acceptable safe range for adults (NIH ODS).
  • Upper limit. The Food and Nutrition Board set a Tolerable Upper Intake Level (UL) of 20 mg/day for adults, including in pregnancy and lactation. The UL is based on reproductive and developmental effects seen in animals.
  • Sport. Boron is not named on the WADA 2026 Prohibited List.

What the research shows

Human data on boron are small, short and often uncontrolled. Many studies come from a few research groups, and several were run in metabolic wards on deliberately low-boron diets, so they test repletion rather than adding boron to a normal diet.

Testosterone and estrogen in men

Study Design Dose and duration Hormone findings
Ferrando and Green 1993 Placebo-controlled; 19 male bodybuilders aged 20–27 2.5 mg/day, 7 weeks No effect on total or free testosterone
Naghii and Samman 1997 Uncontrolled; healthy men 10 mg/day, 4 weeks Estradiol rose from 51.9 to 73.9 pmol/L (≈ 14 to 20 pg/mL; p under 0.004); testosterone only a non-significant trend upward
Naghii et al. 2011 Uncontrolled before-and-after; 8 healthy men 10 mg/day, 1 week Free testosterone rose and estradiol fell; SHBG fell 6 h after the first dose

In the bodybuilding trial, plasma boron rose in the supplemented group. Both groups gained total testosterone, lean body mass and strength over 7 weeks of training, with no difference between boron and placebo (Green and Ferrando, Environ Health Perspect 1994).

The two studies from the Naghii group used the same 10 mg/day dose but reported opposite changes in estradiol: up after 4 weeks in 1997, down after 1 week in 2011. Neither had a placebo group. The 2011 authors also reported lower inflammatory markers (hs-CRP, TNF-α) and higher DHT, cortisol and vitamin D.

About “boron raises testosterone.” This claim rests mainly on the 2011 one-week study of 8 men without a control group. The only randomized, placebo-controlled trial in trained men found no effect on testosterone, lean mass or strength. No controlled trial has shown that boron raises testosterone or builds muscle in men. Other supplements sold for testosterone have their own pages, such as Tongkat Ali, Tribulus terrestris and Zinc.

In a study of workers at a boric acid plant in Turkey, the most highly exposed group (mean estimated boron exposure 14.45 mg/day) showed no adverse changes in FSH, LH or total testosterone (Duydu et al., Arch Toxicol 2011).

Postmenopausal women

In a USDA metabolic-ward study, 12 women aged 48–82 ate a diet supplying about 0.25 mg boron/day for 119 days and then took 3 mg/day (Nielsen et al., FASEB J 1987). Boron markedly raised serum estradiol and testosterone and reduced urinary calcium and magnesium loss. The effects were larger when dietary magnesium was low.

A later study did not reproduce this. Women given a 0.33 mg/day diet for 3 weeks and then 3 mg/day for 3 more weeks showed no change in minerals, sex steroids or bone turnover markers (Beattie and Peace, Br J Nutr 1993).

Osteoarthritis and inflammation

Study Design Dose Result
Newnham 1994 Double-blind, placebo-controlled pilot; 20 people with osteoarthritis 6 mg/day, 8 weeks 50% improved on boron vs 10% on placebo
Scorei et al. 2011 Randomized, double-blind, placebo-controlled; 60 completers with knee osteoarthritis 1.5, 3 or 6 mg/day as calcium fructoborate, 2 weeks Lower inflammatory markers (CRP, fibrinogen, ESR) vs placebo; small lipid changes
Pietrzkowski et al. 2014 Randomized, double-blind, placebo-controlled; 60 adults with self-reported knee discomfort 110 mg calcium fructoborate twice daily, 2 weeks WOMAC score improved more than placebo at day 14 (difference −13.7; p under 0.0001)

The NIH fact sheet describes these results as suggestive but says confirmation from larger controlled trials is needed. The trials are small and short, and the calcium fructoborate trials tested one proprietary ingredient.

Bone

Animal studies link boron deficiency to abnormal bone development and weaker bone. In humans, the NIH fact sheet reports no correlation between boron intake and bone mineral density in 134 Korean women. In a 10-month placebo-controlled trial of 3 mg/day in 28 young women (17 athletes, 11 sedentary), boron changed serum phosphorus and magnesium but did not directly affect bone mineral density (Meacham et al., Environ Health Perspect 1994).

Brain function

In three USDA studies of older adults on controlled diets, low boron intake compared with high intake shifted EEG activity toward slower frequencies. It also worsened performance on tasks of attention, short-term memory and manual dexterity (Penland, Environ Health Perspect 1994). These were deprivation studies; they do not show that extra boron improves cognition in people with normal intakes.

Side effects and risks

At supplement doses

No adverse effects from high boron intake from food or water have been documented. The NIH fact sheet lists no known clinically relevant drug interactions (NIH ODS). The adult UL of 20 mg/day is well above the 3–10 mg/day used in most trials. A separate drinking-water risk assessment derived an acceptable daily intake of 18 mg boron/day for adults (Murray, Regul Toxicol Pharmacol 1995).

Acute poisoning

Accidental ingestion of boric acid or borax (found in some cleaners and pesticides) can cause:

  • nausea, vomiting, abdominal pain and diarrhea;
  • skin flushing and rash;
  • headache, lethargy, restlessness and, in severe cases, convulsions and vascular collapse;
  • kidney injury.

In infants, high intakes have caused anemia, seizures and thinning hair. Doses of 15,000–20,000 mg can be fatal in adults (NIH ODS). In a series of 784 boric acid ingestions reported to two poison centers, 88.3% of patients had no symptoms and none developed severe toxicity (Litovitz et al., Am J Emerg Med 1988).

Reproductive toxicity in animals

High-dose boric acid damages the testes of rats. Rats fed 3,000–9,000 ppm boric acid for up to 9 weeks developed impaired sperm release at the lower doses and testicular atrophy at the higher doses. The atrophy did not recover during 32 weeks of follow-up (Ku et al., Reprod Toxicol 1993).

Safety limits for boron are based on rat data like these (Duydu et al. 2011; Bolt et al. 2020):

Endpoint (rats) No-observed-adverse-effect level
Male fertility 17.5 mg boron/kg/day
Fetal development 9.6 mg boron/kg/day

A 2020 review of field studies in boron-rich areas of China, Argentina and Turkey concluded that blood boron levels in the most heavily exposed workers stayed more than 2–4 times below those linked to reproductive effects in rats. It found no reproductive toxicity in exposed humans (Bolt et al., Arch Toxicol 2020).

Who should be cautious

  • Children. ULs are lower: 3 mg/day at ages 1–3, 6 mg at 4–8, 11 mg at 9–13 and 17 mg at 14–18. For infants, breast milk, formula and food should be the only sources.
  • People with reduced kidney function. Boron is cleared almost entirely by the kidneys (Jansen et al. 1984), and in poisoning cases hemodialysis shortened its half-life (Litovitz et al. 1988). Supplement safety in kidney disease has not been established.
  • Hormone-sensitive conditions. Some small studies reported changes in estradiol and testosterone, in both directions. The clinical meaning is unknown.

Key takeaways

  • A trace element, not a proven nutrient. Boron has no established human function, RDA or Daily Value. Typical US diets supply about 1 mg/day.
  • No good evidence it raises testosterone. The one placebo-controlled trial in bodybuilders (2.5 mg/day, 7 weeks) found no effect on testosterone, lean mass or strength. The positive findings come from tiny, uncontrolled studies.
  • Hormone results conflict. At 10 mg/day, one study found estradiol rose in men and another found it fell.
  • Some early signals in osteoarthritis. Small 2–8 week trials, mostly of calcium fructoborate, reported less joint discomfort and lower inflammatory markers. Larger trials are lacking.
  • Low risk at studied doses. Trial doses of 3–10 mg/day are under the 20 mg/day adult UL. Toxicity is seen with boric acid poisoning and, in animals, at much higher doses that damage the testes.
  • Fast clearance. About 85–90% is absorbed, nearly all is excreted in urine, and the half-life is about 21 hours.

Sources

  1. National Institutes of Health, Office of Dietary Supplements. Boron: Fact Sheet for Health Professionals. Updated June 9, 2022. NIH ODS.
  2. Nielsen FH. Update on human health effects of boron. J Trace Elem Med Biol. 2014;28(4):383–387. PubMed.
  3. Jansen JA, Andersen J, Schou JS. Boric acid single dose pharmacokinetics after intravenous administration to man. Arch Toxicol. 1984;55(1):64–67. PubMed.
  4. Litovitz TL, Klein-Schwartz W, Oderda GM, Schmitz BF. Clinical manifestations of toxicity in a series of 784 boric acid ingestions. Am J Emerg Med. 1988;6(3):209–213. PubMed.
  5. Naghii MR, Samman S. The effect of boron supplementation on its urinary excretion and selected cardiovascular risk factors in healthy male subjects. Biol Trace Elem Res. 1997;56(3):273–286. PubMed.
  6. Naghii MR, Mofid M, Asgari AR, et al. Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines. J Trace Elem Med Biol. 2011;25(1):54–58. PubMed.
  7. Ferrando AA, Green NR. The effect of boron supplementation on lean body mass, plasma testosterone levels, and strength in male bodybuilders. Int J Sport Nutr. 1993;3(2):140–149. PubMed.
  8. Green NR, Ferrando AA. Plasma boron and the effects of boron supplementation in males. Environ Health Perspect. 1994;102(Suppl 7):73–77. PubMed.
  9. Nielsen FH, Hunt CD, Mullen LM, Hunt JR. Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women. FASEB J. 1987;1(5):394–397. PubMed.
  10. 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. Br J Nutr. 1993;69(3):871–884. PubMed.
  11. Newnham RE. Essentiality of boron for healthy bones and joints. Environ Health Perspect. 1994;102(Suppl 7):83–85. PubMed.
  12. 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. Biol Trace Elem Res. 2011;144(1–3):253–263. PubMed.
  13. Pietrzkowski Z, Phelan MJ, Keller R, et al. Short-term efficacy of calcium fructoborate on subjects with knee discomfort: a comparative, double-blind, placebo-controlled clinical study. Clin Interv Aging. 2014;9:895–899. PubMed.
  14. 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. Environ Health Perspect. 1994;102(Suppl 7):79–82. PubMed.
  15. Penland JG. Dietary boron, brain function, and cognitive performance. Environ Health Perspect. 1994;102(Suppl 7):65–72. PubMed.
  16. Murray FJ. A human health risk assessment of boron (boric acid and borax) in drinking water. Regul Toxicol Pharmacol. 1995;22(3):221–230. PubMed.
  17. Ku WW, Chapin RE, Wine RN, Gladen BC. Testicular toxicity of boric acid (BA): relationship of dose to lesion development and recovery in the F344 rat. Reprod Toxicol. 1993;7(4):305–319. PubMed.
  18. Bolt HM, Başaran N, Duydu Y. Effects of boron compounds on human reproduction. Arch Toxicol. 2020;94(3):717–724. PubMed.
  19. Duydu Y, Başaran N, Üstündağ A, et al. Reproductive toxicity parameters and biological monitoring in occupationally and environmentally boron-exposed persons in Bandirma, Turkey. Arch Toxicol. 2011;85(6):589–600. PubMed.
  20. World Anti-Doping Agency. The 2026 Prohibited List. In effect January 1, 2026. WADA 2026 Prohibited List.