Boron and Testosterone: A Small Mineral With a Big Reputation
Search "boron testosterone" and you'll find a lot of confidence. Boron "significantly boosts" testosterone. It raises free testosterone by 25%. It slashes estrogen by half.
Now go and read the actual studies those numbers come from, and something interesting happens: the headline figure traces back to eight men, for seven days, in a pilot study.
That's not a reason to dismiss boron — it's genuinely one of the more intriguing trace elements, and the mechanism people propose for it is clever. But it is a reason to hold the claims loosely. Here's the honest picture.
What Is Boron?
Boron is a trace element found in soil, rocks and water, and it makes its way into our diet mostly through plants.[1] Fruits, nuts, legumes and leafy vegetables are the main sources — avocados, prunes, raisins and almonds are particularly rich.
One thing worth clearing up straight away, because a lot of websites get it wrong: boron is not currently classified as an essential nutrient for humans.[2] Zinc and magnesium are essential — your body can't function without them, and the deficiency states are well described. Boron sits in a more ambiguous category: there's decent mechanistic evidence that small intakes produce measurable biological effects, but its essentiality hasn't been established.[2]
Typical dietary intake sits somewhere around 1–2 mg a day, mostly without anyone thinking about it.
What Research Suggests Boron Does
The best-established area is bone and mineral metabolism. A narrative review of boron and bone health pulled together 11 eligible studies covering 594 subjects, and found the results interesting enough to warrant attention — boron appears to influence calcium metabolism and the growth and maintenance of bone tissue.[1]
Boron also appears to interact with vitamin D, with research suggesting it can increase serum vitamin D concentrations.[1] Since vitamin D is itself involved in bone health and a range of other processes, this is one of the more plausible routes by which a trace element could have knock-on effects.
The Testosterone Question
Now the part everyone actually came for.
Boron appears to interfere with the metabolism of human steroid hormones, and the leading hypothesis for how is genuinely elegant: boron may inhibit certain enzymes that add hydroxyl groups to steroid molecules — a step involved in breaking them down.[1] If that's right, boron wouldn't be increasing hormone production at all. It would be slowing hormone degradation, leaving more of what you already made in circulation.[1]
There's a second proposed route involving SHBG (sex hormone-binding globulin). Most testosterone in your blood travels bound to SHBG, which keeps it inactive; only the unbound portion — "free" testosterone — is biologically available. Lower SHBG means more free testosterone from the same total. So boron's proposed effect isn't about making more, it's about unlocking what's there.
Plausible. Elegant. Now let's look at the actual human data.
What the Studies Actually Found
Two studies do most of the heavy lifting here, both from the same research group.[1]
Naghii et al., 1997: 18 healthy men took 10 mg of boron daily for four weeks. The result? A statistically significant increase in estradiol — and a trend toward higher free testosterone that did not reach statistical significance.[1]
Naghii et al., 2011: 8 healthy men aged 29–50 took 10 mg/day for seven days. This time free testosterone rose, SHBG fell, and estradiol dropped by around 39%.[1]
Read those twice, because there's a problem sitting in plain sight: the two studies found opposite effects on estradiol.One found it went significantly up. The other found it went substantially down. Same research group, same dose, different durations and sample sizes.
And the famous "25% free testosterone" figure that gets quoted everywhere comes from the second one — a pilot study with eight participants over seven days.
The Honest Verdict
So where does that leave boron?
It's a genuinely interesting trace element with a plausible, well-reasoned mechanism and a small body of human research showing measurable hormonal effects. That's more than can be said for a lot of ingredients in this category.
But a recent critical review of boron and related trace elements is blunt about the state of the field: considerable research gaps remain — including dose–response characterisation, toxicity thresholds and controlled human trials — before any of it can be translated into confident recommendations.[2] Small samples, short durations and inconsistent findings are exactly what "preliminary" looks like.
The reasonable position is curiosity without conviction: boron looks worth studying, the mechanism is interesting, and the human evidence is nowhere near settled. Anyone telling you it definitely does anything to your hormones is going further than the data allows.
Safety and Dosage
Boron has a reasonable safety margin at dietary and low supplemental intakes, and the tolerable upper intake level for adults is generally set at 20 mg/day. The studies discussed above used 10 mg/day for short periods. Long-term safety at supplemental doses hasn't been well characterised, which is another gap the reviews specifically flag.[2]
As always, that's a conversation for a healthcare professional or pharmacist who knows your situation.
Common Myths About Boron
Myth 1: Boron is an essential mineral. It isn't currently classified as essential for humans, however interesting the mechanistic evidence is.[2]
Myth 2: Boron significantly increases testosterone. The most-cited result comes from a pilot study of eight men over seven days, and an earlier, larger study didn't find a significant testosterone effect at all.[1]
Myth 3: Boron lowers estrogen. One study found estradiol went up significantly; another found it went down. The evidence contradicts itself.[1]
Getting Boron From Food
Reassuringly boring advice to finish:
- Prunes and raisins — among the richest sources going
- Avocados
- Almonds and other nuts
- Legumes — beans and chickpeas
- Leafy vegetables
A varied diet with fruit, nuts and vegetables in it supplies boron without any effort at all.
Boron is a good example of why reading past the headline matters. It's a real trace element doing real things in the body, with a mechanism that makes sense — and simultaneously, the confident numbers circulating about it rest on a much thinner foundation than their confidence suggests. Both things are true, and the interesting version of the story is the one that holds them together.
References
- Rondanelli M, Faliva MA, Peroni G, et al. Pivotal role of boron supplementation on bone health: A narrative review. Journal of Trace Elements in Medicine and Biology. 2020;62:126577. Available at: https://www.sciencedirect.com/science/article/pii/S0946672X20301425
- Dietary Lithium, Silicon, and Boron: An Updated Critical Review of Their Roles in Metabolic Regulation, Neurobiology, Bone Health, and the Gut Microbiome. Nutrients. 2025. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12899721/
- Naghii MR, Mofid M, Asgari AR, Hedayati M, Daneshpour MS. Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines. Journal of Trace Elements in Medicine and Biology. 2011;25(1):54-58.
- Pizzorno L. Nothing Boring About Boron. Integrative Medicine: A Clinician's Journal. 2015;14(4):35-48.
This article is intended for general educational purposes only and does not constitute medical advice. The research described is preliminary and evolving. Individual health needs vary; please consult a qualified healthcare professional or pharmacist regarding your own circumstances before starting any new supplement.
