Boron

What it is

Boron is a trace element found mostly in plant foods. It is not classed as an essential nutrient for humans, because no clear biological function has been identified. Supplements supply it in many forms, including sodium borate, boron citrate, boron glycinate and calcium fructoborate.

What the research says

Boron is promoted for bones, joints and testosterone. The human evidence is thin: small, short trials. A narrative review of 11 studies suggested benefits for bone, but it was not a systematic review with certainty ratings. A 7-week placebo-controlled trial in bodybuilders found no effect on testosterone, lean mass or strength. A one-week uncontrolled study of 8 men reported a rise in free testosterone. Two short trials of boron or calcium fructoborate reported less knee or joint discomfort. Very large doses, usually boric acid or borax poisoning, cause stomach, skin and nervous system effects and can be fatal.

Evidence grade: Limited evidence.

What goes wrong

Human poisoning reports show boric acid can be fatal at high doses, although in one series of 784 poisonings 88% had no symptoms and none died. (Source 1)

• Case series, Low certainty.
• Size: 784 poisonings in one series, plus case reports.
• Who: People who swallowed boric acid.
• How long: Acute.
• Result: Reported minimal lethal dose 15-20 g in adults, 2-3 g in infants.
• Funding: Government review (ATSDR)

However, a review of 784 human poisonings with boric acid (10–88 g) reported no fatalities, with 88% of cases being asymptomatic.

Reported symptoms of accidental boric acid or borax ingestion include nausea, vomiting, diarrhoea, rash, convulsions and vascular collapse; high intakes in infants have caused anaemia and seizures (NIH ODS). (Source 2)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: Accidental ingestion; infants.
• How long: Acute.
• Result: Not applicable.
• Funding: Government.

In infants, high boron intakes have caused anemia, seizures, erythema, and thin hair.

Animal studies identify the reproductive system and developing fetus as the most sensitive targets of boron toxicity. This is animal evidence and forms the basis of the upper limits. (Source 1)

• Animal study, Certainty not rated.
• Size: Not applicable.
• Who: Laboratory animals.
• How long: Acute and intermediate exposure.
• Result: Not applicable.
• Funding: Government review (ATSDR)

Oral exposure animal studies have clearly identified the reproductive system and developing fetus as the most sensitive targets of boron toxicity

What the evidence supports

A small uncontrolled study reported that 10 mg boron a day for one week raised free testosterone and lowered estradiol in 8 healthy men. (Source 3)

• Case series, Very low certainty.
• Size: 8 men.
• Who: Healthy male volunteers.
• How long: 1 week.
• Result: Free testosterone rose and estradiol fell significantly; no effect sizes in the abstract.
• Funding: Not stated in the abstract.

After one week (in samples taken at 8.00 A.M, only), the mean plasma free testosterone increased and the mean plasma estradiol decreased significantly.

A 2-week randomised trial reported calcium fructoborate (110 mg twice daily) reduced self-reported knee discomfort compared with placebo. (Source 4)

• Randomized trial, Low certainty.
• Size: 60 participants.
• Who: Adults with self-reported knee discomfort.
• How long: 2 weeks.
• Result: MPQ difference -8.9 (P<0.0001) and WOMAC -13.73 (P<0.0001) at day 14; WOMAC -5.3 at day 7 (P=0.06)
• Funding: Not stated in the abstract; authors reported no conflicts of interest.

Estimated treatment differences for the MPQ score were -5.8 (P=0.0009) and -8.9 (P< 0.0001) at Day 7 and 14, respectively.

A narrative review of 11 studies suggested boron may support bone health, but it was not a systematic review and did not grade certainty. (Source 5)

• Expert review, not systematic, Low certainty.
• Size: 11 studies, 594 subjects.
• Who: Humans.
• How long: Varied.
• Result: Not pooled.
• Funding: Not stated.

Despite the number of studies considered being low, the number of subjects studied is high (594) and the results are interesting.

What the evidence does not support

A 7-week placebo-controlled trial of 2.5 mg boron a day in male bodybuilders found no effect on testosterone, lean body mass or strength. (Source 6)

• Randomized trial, Low certainty.
• Size: 19 men.
• Who: Male bodybuilders aged 20-27.
• How long: 7 weeks.
• Result: No significant effect on any dependent variable (analysis of variance)
• Funding: Not stated in the abstract.

Analysis of variance indicated no significant effect of boron supplementation on any of the dependent variables.

In an observational study of 134 Korean women, boron intake was not significantly correlated with bone mineral density (reported by NIH ODS). (Source 2)

• Survey study, Very low certainty.
• Size: 134 women.
• Who: Korean women, average age 41.
• How long: Not applicable.
• Result: No significant correlation.
• Funding: Not stated.

However, in an observational study in 134 Korean women (average age 41 years), boron intakes (mean of 0.9 mg/day) were not significantly correlated with bone mineral density in the lumbar spine or femoral regions.

Where the research disagrees

Whether boron supplements raise testosterone

• Ferrando & Green, 1993, Placebo-controlled trial, 19 men, 7 weeks: boron supplementation had no effect on these measures. (Source 6)
• Naghii et al., 2011, Uncontrolled study, 8 men, 1 week: After one week (in samples taken at 8.00 A.M, only), the mean plasma free testosterone increased (Source 3)

How much

• Reference intake: None. The US Food and Nutrition Board (2001) found the data insufficient to set an RDA, AI or EAR for boron, and boron is not classed as essential for humans. (Source 2)
• Upper limit: The Food and Nutrition Board (2001) set a UL of 20 mg/day for adults, based on reproductive and developmental effects in animals (as reported by NIH ODS, 2022). EFSA's upper level for adults is 10 mg/day, as cited in Rondanelli et al. 2020. (Source 2)
• Studied: 2.5 mg boron a day for 7 weeks in male bodybuilders. (Source 6)
• Studied: 10 mg boron a day for one week in 8 healthy men. (Source 3)
• Studied: 110 mg calcium fructoborate twice a day for 2 weeks. (Source 4)

A common belief, and what the research shows

The belief: Boron is a proven testosterone booster.

What the research shows: The only placebo-controlled trial we reached, in bodybuilders, found 'no significant effect of boron supplementation on any of the dependent variables', including testosterone. The positive report came from an uncontrolled study of 8 men over one week.

Questions and answers

What is it?

Boron is a trace element found mainly in plant foods. It is not classed as an essential nutrient for humans, because no clear biological role has been identified. (Source 2)

What does it do in the body?

Researchers think boron plays a part in calcium metabolism and bone, but its exact role in humans is not established, and there is no clear guidance on supplement amounts. (Source 5)

Is it good or bad for you?

The amounts in food are not known to be harmful. Evidence of benefit from supplements is limited to small, short trials, and a placebo-controlled trial found no effect on testosterone or strength. Very large doses, usually from swallowing boric acid or borax, are toxic and can be fatal. (Source 1)

How do you get more of it?

Intake comes from plant foods and drinks such as coffee, and from supplements that use many forms: sodium borate, boron citrate, boron glycinate and calcium fructoborate, among others. Trials gave 2.5 to 10 mg of boron a day. (Source 2)

If it is harmful, what reduces it?

Boron from food is not considered harmful. Serious poisoning comes from swallowing boric acid or borax in household cleaners and pesticides; that is a medical emergency. We found no studies of ways to lower boron in healthy people. (Source 2)

Why might someone be low in it or missing it?

Intake depends mostly on how many plant foods a person eats, because plants hold the most boron. No deficiency disease is established in humans, and no RDA exists. (Source 2)

Which whole foods contain it or feed it?

Plant foods hold the most boron: fruit, tubers and legumes. Avocados, prunes, raisins and peanuts are rich. In the US diet the main sources are coffee, milk, apples, beans and potatoes. Wine, cider and beer also contain boron. (Source 2)

What happens if you do not have it?

No human deficiency disease has been established. Limited data suggest low boron might affect mental alertness and executive function, but this evidence is weak. (Source 2)

How can you test for it?

Boron is not routinely measured in clinical practice. Urine boron tracks recent intake in studies, but no validated test of boron status for individuals exists. (Source 2)

References

1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Boron, Chapter 2: Relevance to Public Health. 2010. Read the source
2. NIH Office of Dietary Supplements. Boron - Health Professional Fact Sheet (updated June 9, 2022). 2022. Read the source
3. Journal of Trace Elements in Medicine and Biology. Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines. 2011. PMID 21129941, DOI 10.1016/j.jtemb.2010.10.001. Read the source
4. Clinical Interventions in Aging. Short-term efficacy of calcium fructoborate on subjects with knee discomfort: a comparative, double-blind, placebo-controlled clinical study. 2014. PMID 24940052, DOI 10.2147/CIA.S64590. Read the source
5. Journal of Trace Elements in Medicine and Biology. Pivotal role of boron supplementation on bone health: A narrative review. 2020. DOI 10.1016/j.jtemb.2020.126577. Read the source
6. International Journal of Sport Nutrition. The effect of boron supplementation on lean body mass, plasma testosterone levels, and strength in male bodybuilders. 1993. PMID 8508192, DOI 10.1123/ijsn.3.2.140. Read the source