Boron is often found in "testosterone" complexes and bone mineral formulas. However, what kind of element is it, where does it enter the body, and what are its effects that have a scientific basis? The editors have broken down the chemistry, physiology and key research on boron to separate the established facts from the hypotheses.
Boron as a trace element: chemistry and sources
Boron is a chemical element with atomic number 5, a light non-metal that almost never occurs in free form in nature. In soil, water and living organisms, it exists mainly in the form of boric acid and its salts - borates. It is in this form that boron gets into plants, and through them into our diet.
Boron is definitely necessary for plants: it takes part in the construction of the cell wall, the transport of sugars and the development of pollen. For humans, the situation is more complicated. Boron does not have an officially established recommended daily allowance, and the question of whether it is an "essential" trace element in the strict sense is still debated in the scientific literature. At the same time, enough data have been accumulated to consider it biologically active and useful in physiological amounts.
The main food sources of boron are products of plant origin. It is most abundant in fruits (especially dried fruits), nuts, legumes, avocados, and leafy vegetables. Coffee, wine and drinking water, the boron content of which depends on the region, can make a significant contribution to consumption. Animal products contain little of it.
A normal mixed diet for an adult provides approximately 1–3 mg of boron per day; vegetarians and people who eat a lot of fruits and nuts have higher incomes. For comparison, most dietary supplements with boron contain 3 mg of the element per serving, which is about double the usual intake.
| Product group | Relative boron content | Editorial comment |
|---|---|---|
| Dried fruits (raisins, prunes, dried apricots) | High | One of the most concentrated food sources |
| Nuts and peanut butter | High | Almonds, hazelnuts, peanuts |
| Beans, avocado | Medium–high | Handy daily source |
| Fresh fruits, vegetables | Medium | Depends on the soil of the growing region |
| Meat, fish, dairy products | Low | Minor contribution to the diet |
How boron is absorbed and excreted
Boron belongs to elements with very high bioavailability. Boric acid and most borates from food and supplements are almost completely absorbed in the small intestine: in physiological studies, absorption was estimated at the level of more than 85–90%. For comparison, absorption of iron or zinc from food is several times lower.
In the blood, boron circulates mainly in the form of uncharged boric acid, which easily passes through cell membranes and is evenly distributed in the body's aqueous environments. Some accumulates in bone tissue, nails and hair, allowing researchers to use these tissues as markers of long-term exposure.
Boron is excreted mainly by the kidneys with urine, and quite quickly: most of the dose taken leaves the body within a few days. Because of this, the level of boron in the plasma largely reflects recent consumption, and no stable "depot" is formed in the body. This fact is also important for safety: in people with preserved kidney function, accumulation at moderate doses is unlikely.
On the other hand, when kidney function is impaired, excretion slows down and boron concentration can increase. That is why kidney disease is considered one of the main reasons for caution when taking boron supplements.
Biological roles of boron: what science knows
Unlike classical microelements, no enzyme in which it would be an obligatory cofactor has been described for boron. Instead, it is known that boric acid is able to form complexes with molecules that contain several hydroxyl groups located next to each other: sugars, some vitamins, nucleotides. Through such interactions, boron probably affects the stability of membranes and the work of signaling molecules.
Most attention has been paid to the role of boron in the metabolism of calcium, magnesium, and vitamin D. In a classic experiment by Nielsen et al. (1987), postmenopausal women received 3 mg of boron per day after a period of a low-boron diet. Against this background, urinary calcium and magnesium loss decreased, and serum estradiol and testosterone levels increased. It was this work that became the starting point for further interest in boron.
Epidemiological observations, summarized by Newnham (1994), indicated that regions with low boron content in the soil and diet are more likely to have joint disease. Such data do not prove a causal relationship, but have prompted the study of boron as a factor in bone and joint health.
Another direction is the influence on inflammatory processes. In small human studies, boron supplementation was associated with reductions in inflammatory markers such as C-reactive protein and pro-inflammatory cytokines. The mechanism is explained, among other things, by the effect on enzymes involved in the inflammatory cascade, but these data are still limited.
- Bones and minerals: reduction of calcium and magnesium losses, possible participation in vitamin D metabolism.
- Steroid hormones: influence on the ratio of free and bound fractions of sex hormones.
- Inflammation: reduction of selected inflammatory markers in short studies.
- Cognitive function: Early work suggested a link between low boron intake and poorer attention performance, but evidence was scarce.
Boron and hormones: mechanistic hypotheses
For the sports audience, the main reason for interest in boron is its possible effect on testosterone and estradiol. Here it is important to distinguish between total testosterone, which is measured in a standard analysis, and free testosterone — a small portion of the hormone that is not bound to transport proteins and directly acts on tissues.
Most of the testosterone in the blood is bound to sex hormone-binding globulin (SHBG) and albumin. One hypothesis is that boron may reduce the activity or level of SHBG, thereby increasing the proportion of free testosterone without increasing total production of the hormone. This is consistent with the results of a short study by Naghii et al. (2011).
In that work, healthy men received 10 mg of boron per day for a week. The authors reported an increase in free testosterone and a decrease in plasma estradiol, as well as a decrease in the levels of inflammatory markers. However, there were only eight participants, no placebo control group, and the follow-up period was very short.
The second hypothesis concerns the effect of boron on enzymes metabolizing steroid hormones, in particular on hydroxylation processes. There is still little direct evidence of this in humans. Therefore, the "boron - hormones" mechanism remains a plausible, but not conclusively confirmed model, and the magnitude of the effect in real conditions is unknown.
We presented a detailed analysis of research specifically on athletes in a separate material; here we only note that in a controlled study by Ferrando and Green (1993) in bodybuilders, intake of 2.5 mg of boron per day for seven weeks did not give advantages over placebo either in terms of testosterone, strength, or muscle mass.
Does an athlete need boron?
Based on the available data, the editors consider boron not as a "testosterone booster", but as a trace element, the sufficient supply of which is part of a balanced diet. For people who regularly eat fruits, vegetables, nuts and legumes, an additional intake, most likely, will not give a noticeable effect on sports results.
Boron may be appropriate in the composition of complex mineral supplements, in particular for the maintenance of bone tissue, if the diet is poor in plant foods. It is better to make such decisions taking into account the general diet and, if necessary, after consulting a doctor or nutritionist.
It is important to remember that there is not too much distance between useful and excessive amounts of boron. The upper tolerable intake level established by EFSA is 10 mg per day for adults, while the US Institute of Medicine has set it at 20 mg. We talk about excess symptoms and risk groups in separate articles.
It is also worth considering the quality of the product. Supplements for athletes are sometimes contaminated with prohibited substances, so it is advisable for professional athletes to choose products that have passed independent certification.
Editorial conclusions
Boron is a light element that enters the body mainly with plant food, is almost completely absorbed and quickly excreted by the kidneys. It does not have a set daily rate, but is involved in the exchange of calcium, magnesium and steroid hormones.
The best-known studies show effects of boron on the ratio of free and bound testosterone and on estradiol levels, but they are small and short-lived. Controlled work on athletes did not confirm the anabolic effect.
Practical conclusion: the priority is a diet with a sufficient amount of fruits, vegetables and nuts; Boron supplements are an additional, not a key tool, and their dose should not approach the upper limit.
To get a complete picture, we advise you to read our materials "The benefits of Boron for athletes: the evidence base", "Side effects of Boron" and "How to take Boron: dosage, time of administration, duration".
List of used literature
- 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):394â397.
- 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):54â58.
- 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):140â149.
- Newnham RE. Essentiality of boron for healthy bones and joints. Environ Health Perspect. 1994;102(Suppl 7):83â85.
- Pizzorno L. Nothing boring about boron. Integr Med (Encinitas). 2015;14(4):35â48.
- Nielsen FH, Meacham SL. Growing evidence for human health benefits of boron. J Evid Based Complementary Altern Med. 2011;16(3):169â180.
- Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington (DC): National Academy Press; 2001.
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Opinion related to the tolerable upper intake level of boron (sodium borate and boric acid). EFSA Journal. 2004.
