Supplements: Boron
10mg boron daily for 7 days raised free testosterone 28.3%, lowered estradiol 39%, and reduced SHBG 9% in men (Naghii et al. 2011, PMID 21129941).
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Evidence Tier | 3 | tier | Weak — small human studies, effects most relevant to deficient populations, limited independent replication |
| Free Testosterone Increase | +28.3 | % | After 10mg/day × 7 days in men; baseline status not controlled for deficiency |
| Estradiol Reduction | −39 | % | Same study; reduction in 17β-estradiol over 1-week supplementation period |
| Upper Tolerable Intake | 20 | mg/day | Set by both US and EU regulatory bodies; no serious adverse effects below this level |
| Typical Dietary Intake | 0.5–3.5 | mg/day | Western diet range; plant-heavy diets trend toward upper end |
| Prunes Boron Content | 4.4 | mg/100g | Highest common food source; raisins 2.2mg/100g, almonds 2.3mg/100g |
Boron occupies an unusual position in nutrition science: it is not classified as an essential nutrient in humans (no deficiency syndrome has been formally defined), yet it demonstrably affects hormone metabolism, bone mineral density, and inflammatory markers at physiological doses.
Mechanism of Action
Boron’s hormonal effects operate through two primary pathways. First, it reduces sex hormone binding globulin (SHBG), the protein that renders testosterone biologically inactive. Lower SHBG means more free (bioavailable) testosterone circulates in blood. Second, boron modulates the conversion of steroid hormones — specifically, it appears to shift estrogen metabolism away from 17β-estradiol toward less potent metabolites, while increasing 3α,5α-tetrahydroprogesterone. These effects suggest boron functions as a mild modulator of the sex hormone axis rather than a direct testosterone precursor.
| Effect | Dose | Change | Study PMID | Population | Notes |
|---|---|---|---|---|---|
| Free testosterone | 10mg/day | +28.3% | 21129941 | 8 men, 7 days | Small sample, no deficiency screen |
| Estradiol (17β) | 10mg/day | −39% | 21129941 | 8 men, 7 days | Large effect; replication needed |
| SHBG | 10mg/day | −9% | 21129941 | 8 men, 7 days | Modest but consistent |
| Inflammatory cytokines | 10mg/day | Reduced hsCRP | 21129941 | 8 men, 7 days | Secondary finding |
| Bone density | 3mg/day | Maintained | Observational | Post-menopausal women | Mechanism via Ca/Mg retention |
| Cognitive function | 3mg/day | Improved scores | Animal + small human | Deficient subjects | Not replicated at scale |
Dietary vs. Supplemental Sources
Most people in Western countries consume 1-3.5mg of boron daily through diet. Plant foods dominate: prunes (4.4mg/100g), almonds (2.3mg/100g), raisins (2.2mg/100g), and avocados are leading sources. Anyone eating abundant fruit and nuts is unlikely to be deficient. The Naghii 2011 study used 10mg — a dose roughly 3-7× typical dietary intake — which may explain the pronounced effects.
Practical Considerations
Boron glycinate and boron citrate offer better bioavailability than inorganic forms. Standard supplemental doses range 3-10mg/day. The US and EU have both set the tolerable upper intake level at 20mg/day, well above common supplement doses. Unlike many “testosterone booster” compounds, boron at least has plausible mechanistic data and one human trial showing hormone effects — though the study size (n=8) demands caution before attributing it the same evidence weight as established interventions like vitamin D or zinc in genuinely deficient men.
Related Pages
Sources
- 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;25(1):54-58.
- Nielsen FH. Update on the possible nutritional importance of silicon. J Trace Elem Med Biol. 2014;28(4):379-382.
- Miljkovic D et al. Boron and aging. Aging. 2021;13(2):2810-2825.
Frequently Asked Questions
Does boron actually increase testosterone?
A small 2011 study found 10mg boron daily for 7 days raised free testosterone by 28.3% in men. However, this study had 8 participants and did not screen for baseline boron deficiency, so the effect may be confined to people with low intake. Most Western adults get 1-3mg/day from food.
What is the best form of boron supplement?
Boron glycinate and boron citrate are the most bioavailable supplemental forms. Boron trioxide (found in some cheap products) has lower solubility. Standard effective doses are 3-10mg elemental boron per day.
Can you get enough boron from food?
Yes, if you eat fruits, nuts, and legumes regularly. Prunes contain 4.4mg/100g, almonds 2.3mg/100g, and raisins 2.2mg/100g. Someone eating a varied diet with abundant produce likely does not need supplemental boron.
Is boron safe long-term?
Doses up to 20mg/day are considered safe per US and EU regulatory bodies. At very high doses (above 100mg/day in animal studies), reproductive toxicity has been observed. The 3-10mg supplemental range maintains a large safety margin.
Does boron help with joint pain?
Observational data links higher boron intake regions with lower arthritis rates, and boron deficiency impairs calcium and magnesium metabolism affecting bone. However, controlled human RCTs for joint pain are limited and no therapeutic dose is established.