Boron After 40: Hormones, Bones and Realistic Expectations
Boron is a trace element that most people have never thought about, yet it regularly appears in "testosterone boosters" aimed at men over 40 and in bone formulas for women around the menopause. The research behind it is real but thin, and the gap between what studies found and what labels promise is wide. Our editorial team examines what boron can and cannot do in midlife.
Boron in the diet and in the body
Boron is present in plant foods: fruit such as apples, pears and prunes, dried fruit, nuts, pulses, avocado and wine. Typical adult intakes in Western diets are around 1–2 mg a day, with higher amounts in vegetarians and people who eat plenty of fruit and nuts.
It is not officially classed as an essential nutrient for humans, and no Reference Nutrient Intake exists in the UK. Nevertheless, a body of research suggests it influences the metabolism of calcium, magnesium and vitamin D, and the activity of several steroid hormones.
Boron is absorbed efficiently and excreted mostly in urine, so blood levels drop quickly when intake falls. This rapid turnover is one reason why short supplementation studies can show measurable changes in a matter of days.
After 40, interest in boron typically centres on three areas: the slow decline in testosterone in men, bone health during and after the menopause, and joint comfort in people with osteoarthritis.
What studies show about hormones
The study most often quoted on supplement labels is a small trial by Naghii and colleagues. Healthy men took 10 mg of boron daily for one week; free testosterone rose, oestradiol fell and some inflammatory markers decreased. The changes were statistically significant but the sample was tiny and the duration very short.
Earlier, Nielsen's group studied postmenopausal women on a low-boron diet and then gave 3 mg per day. They reported reduced urinary calcium and magnesium losses and increases in circulating oestradiol and testosterone, particularly when magnesium intake was low.
By contrast, a study by Ferrando and Green in male bodybuilders found that 2.5 mg of boron per day over seven weeks did not increase lean mass, strength or testosterone compared with placebo. Training alone accounted for the improvements seen.
Put together, the data suggest boron can nudge hormone balance in some circumstances, especially when baseline intake is low, but there is no good evidence that it produces meaningful gains in muscle or strength.
Bones, joints and the menopause
Bone health is the area where boron's biology looks most coherent. It appears to interact with vitamin D and oestrogen metabolism and to reduce urinary calcium loss, all relevant to bone density in midlife women. However, long-term trials showing fewer fractures do not exist.
For osteoarthritis, epidemiological observations that regions with low boron intake have higher rates of arthritis, together with a few small trials, led to interest in boron for joint comfort. Pizzorno's review summarises this literature while acknowledging its limitations.
For women over 40, the established foundations of bone health remain adequate calcium, vitamin D (the UK advises 10 micrograms a day, particularly in autumn and winter), regular weight-bearing and resistance exercise, not smoking and moderating alcohol. Boron, at best, is a minor addition to these.
Women with a history of hormone-sensitive conditions, such as certain breast cancers or endometriosis, should be cautious, because boron may raise oestrogen levels. Those on hormone replacement therapy should discuss supplements with their GP.
Safety limits and who should avoid it
In the UK, the Expert Group on Vitamins and Minerals set a safe upper level for supplemental boron of 9.6 mg per day for adults, based on 0.16 mg per kilogram of body weight. The EU's tolerable upper intake level is 10 mg per day for adults. Most supplements contain 3–6 mg, which sits comfortably within these limits when combined with food.
Very high doses are toxic, and boric acid is classified in the EU and UK as toxic to reproduction. This is relevant when products are taken at multiples of the labelled dose or combined with several other boron-containing formulas.
| Group | Recommendation |
|---|---|
| Healthy adults over 40 | Food first; 3 mg/day from supplements is a typical, low-risk amount |
| Kidney disease | Avoid without medical advice, as boron is cleared by the kidneys |
| Hormone-sensitive conditions | Discuss with specialist before use |
| Pregnancy, trying to conceive | Avoid supplements |
| Men on testosterone therapy | Inform prescribing clinician; effect on results unclear |
Signs of excess can include nausea, vomiting, diarrhoea and skin rashes. If these appear, stop the supplement and seek advice.
Conclusions of the editorial team
Boron is a plausible, inexpensive and generally safe supplement at modest doses, but it is not a testosterone booster in any meaningful sense. The hormonal changes seen in short studies are small and have not translated into more muscle or strength.
For midlife men and women, the best returns come from:
- a diet rich in fruit, nuts and pulses, which supplies boron naturally;
- resistance training at least twice a week;
- adequate sleep, vitamin D and protein;
- checking hormone levels through a GP if symptoms suggest a deficiency.
If you do choose to supplement, stay well within the UK safe upper level and avoid stacking multiple products that contain boron.
Related topics worth reading next include our guides to vitamin D for active adults, testosterone testing after 40 and magnesium for sleep and recovery.
References
- 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. J Trace Elem Med Biol. 2011;25(1):54–58.
- 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.
- 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.
- Pizzorno L. Nothing boring about boron. Integr Med (Encinitas). 2015;14(4):35–48.
- Green NR, Ferrando AA. Plasma boron and the effects of boron supplementation in males. Environ Health Perspect. 1994;102(Suppl 7):73–77.
- Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals. London: Food Standards Agency; 2003.
