Boron: What the Research Says, and What to Check on the Label
Boron is a trace mineral people take for testosterone, joints and bones; the trials are small and short, and the results are mixed. Most bone and mineral studies used 3 mg a day, and the adult upper limit is 20 mg. It is not an essential nutrient. Our pick: NOW Boron 3 mg.
By Erin Rose Updated October 19, 2026 How we score
What to buy
NOW Boron 3 mg is our pick. One capsule gives the 3 mg most bone and mineral studies used, with nothing else added, for $0.06 a day at Vitacost’s price. No boron product is on a public testing list.
NOW Boron 3 mg
Our pick · 3 mg, boron only
Want a brand certificate of analysis? Life Extension gives the same 3 mg for $0.05 a day and adds 25 mg of vitamin B2.
Life Extension Boron
3 mg · certificate of analysis
Where to go next
- Best boron: the products we compared, ranked.
- Boron dosage guide: how much to take, limits by age, and a calculator.
What boron does
Boron is a trace mineral in plant foods. The NIH does not class it as an essential nutrient, so it has no recommended daily amount.
| Goal | Evidence | What trials found |
|---|---|---|
| Testosterone | Mixed, tiny trials | Free testosterone rose after 10 mg a day for a week in 8 men (Naghii 2011); 2.5 mg a day for 7 weeks did nothing in 19 bodybuilders (Ferrando 1993). |
| Joints | Early, small trials | Calcium fructoborate eased knee discomfort over 2 weeks in 60 adults (Pietrzkowski 2014); the NIH says this needs more trials. |
| Bones | Mixed, mostly markers | 3 mg a day cut calcium and magnesium lost in urine in 12 women after months on a very low boron diet (Nielsen 1987); another trial found no effect (Beattie 1993), and the NIH reports a trial where boron did not change bone density. No trial measured fractures. |
| Period pain | One trial | 10 mg a day around two periods lowered pain in 113 students (Nikkhah 2015). |
How much boron
Most bone and mineral studies used 3 mg a day; hormone trials used up to 10 mg. The adult upper limit is 20 mg a day, and lower for children. See the dosage guide.
Is boron safe?
The NIH lists no known drug interactions. It has no data on harm from boron in food or water, which is not proof of safety, and its 20 mg limit comes from animal studies of harm to reproduction and growth. A few things to check:
- Add up all your boron, including multivitamins and joint formulas, and stay under 20 mg a day as an adult.
- Children have lower limits: 3 mg a day at ages 1 to 3, up to 17 mg at 14 to 18.
- Pregnant or breastfeeding: the limit is the same as for others your age (20 mg at 19 or older, 17 mg at 14 to 18), but ask your doctor first.
Questions people ask
Where does boron come from in food?
Fruits, vegetables and legumes. Food gives most adults about 1 to 1.5 mg a day (NIH Office of Dietary Supplements).
Is boron the same as borax or boric acid?
The body turns most boron you swallow into boric acid, and some trials gave boric acid itself. The difference is the amount: supplements give 3 to 10 mg a day, under the adult limit. Never swallow household borax or boric acid.
Sources
- NIH Office of Dietary Supplements. “Boron: Fact Sheet for Health Professionals.” ods.od.nih.gov
- Naghii MR, et al. “Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines.” J Trace Elem Med Biol. 2011. PubMed 21129941
- Ferrando AA, et al. “The effect of boron supplementation on lean body mass, plasma testosterone levels, and strength in male bodybuilders.” Int J Sport Nutr. 1993. PubMed 8508192
- Pietrzkowski Z, 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. PubMed 24940052
- Nielsen FH, et al. “Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women.” FASEB J. 1987. PubMed 3678698
- Beattie JH, et al. “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. PubMed 8329361
- Nikkhah S, et al. “Effects of boron supplementation on the severity and duration of pain in primary dysmenorrhea.” Complement Ther Clin Pract. 2015. PubMed 25906949